WO2016209813A1

WO2016209813A1 - Triblock copolymer with vinyl alcohol and/or vinyl acetate residues, synthetic precursors thereof, and a polymer membrane comprising the triblock copolymer

Info

Publication number: WO2016209813A1
Application number: PCT/US2016/038518
Authority: WO
Inventors: E. Bryan Coughlin; Haomiao YUAN; Toshinori Kato
Original assignee: Kuraray Co Ltd; University of Massachusetts Boston; University of Massachusetts Amherst
Current assignee: Kuraray Co Ltd; University of Massachusetts Boston; University of Massachusetts Amherst
Priority date: 2015-06-23
Filing date: 2016-06-21
Publication date: 2016-12-29
Anticipated expiration: 2017-12-23

Abstract

A triblock copolymer has the structure ( l ) wherein A includes a polyolefin, each Z can include a poly(vinyl acetate), a poly(vinyl alcohol), or a poly(vinyl acetate-co-vinyl alcohol), and L¹, L², R¹, R² and y are defined herein. The triblock copolymer can be amphiphilic when the Z includes a poly(vinyl alcohol), or a poly(vinyl acetate-co-vinyl alcohol). Also described are synthetic precursors to the triblock copolymer that include a mid-functional polymer and a chain transfer agent. The triblock copolymer and films prepared therefrom are useful in applications including separation of oil-water mixtures.

Description

TRIBLOCK COPOLYMER WITH VINYL ALCOHOL AND/OR VINYL ACETATE RESIDUES, SYNTHETIC PRECURSORS THEREOF, AND A POLYMER MEMBRANE

COMPRISING THE TRIBLOCK COPOLYMER

BACKGROUND OF THE INVENTION

[0001] Amphiphilic block copolymers (ABCs) have gained increasing interest due to potential applications including drug delivery and emulsion stabilization. ABCs can self-assemble to generate various morphologies including spheres, cylinders, and vesicles in aqueous solution or using a selective solvent. Many studies of block copolymers in aqueous solution have focused on hydrophobic polymers with hydrophilic poly(ethylene oxide) (PEO) or poly(acrylic acid) (PAA). In contrast, very few studies have focused on the use of poly(vinyl alcohol) (PVOH)-containing amphiphiles, largely due to the lack of well-defined PVOH-containing block copolymers. Water soluble PVOH homopolymers, typically obtained by hydrolysis of poly(vinyl acetate) (PVAc), are of interest for applications including adhesion, medicine, and tissue engineering. See, e.g., Peppas, N. A.; Bures, P.; Leobandung, W.; Ichikawa, H., European Journal of Pharmaceutics and Biopharmaceutics, 2000, 50 (1), 27; Lee, K. Y.; Mooney, D. J., Chemical Reviews, 2001, 101 (7), 1869.

[0002] PVAc can be synthesized by reversible addition-fragmentation chain transfer (RAFT) and cobalt- mediated radical polymerization (CMRP). See, e.g., Stenzel, M. H.; Cummins, L.; Roberts, G. E.; Davis, T. P.; Vana, P.; Barner-Kowollik, C, Macromolecular Chemistry and Physics, 2003, 204 (9), 1160; Debuigne, A.; Caille, J.-R.; Jerome, R., Angewandte Chemie International Edition, 2005, 44 (7), 1101. However, controlled living radical polymerization (CRP) by sequential RAFT and CMRP to obtain PVAc block copolymers is difficult due to the high reactivity and poor stability of its propagating radicals relative to those of other monomers. An atom transfer radical polymerization (ATRP) initiator which combines the functionality of a RAFT agent has been used to synthesize polystyrene-poly( vinyl acetate) amphiphilic block copolymers (PS-^-PVAc). See, e.g., Nicolay, R.; Kwak, Y.; Matyjaszewski, K., Chemical Commununications 2008, (42), 5336. However, because the ester linkage between PS and PVAc is not hydrolytically stable, the block copolymer cannot be hydrolyzed to generate PS-&-PVOH.

[0003] Efforts to prepare hydrolytically stable PVOH-containing amphiphilic block copolymers include synthesizing functionalized PVAc, for example, by CMRP, and using the functionalized PVAc as a macroinitiator for polymerization of the hydrophobic block, for example, using RAFT or ATRP. This approach has allowed for the formation of PVOH-containing block copolymers by hydrolysis of the PVAc counterparts. See, e.g., Debuigne, A.; Caille, J.-R.; Willet, N.; Jerome, R., Macromolecules, 2005, 38 (23), 9488.

[0004] An alternative approach to block copolymerization uses a method combining mechanistically incompatible monomers, rather than relying solely on controlled living radical polymerization techniques. Exemplary block copolymer syntheses combining mechanistically incompatible monomers include combinations of Ziegler-Natta

polymerization with nitroxide mediated living free radical polymerization (NMP), ring- opening polymerization (ROP) with RAFT, ring-opening metathesis polymerization (ROMP) with ATRP, and ROMP with RAFT. For example, a tandem ROMP-RAFT method was employed to synthesize well-defined styrene-butadiene-styrene (SBS) triblock copolymers and alkylacrylate-butadiene-alkylacrylate triblock copolymers. See, e.g., Bowden, N. B.; Dankova, M.; Wiyatno, W.; Hawker, C. J.; Waymouth, R. M., Macromolecules, 2002, 35 (25), 9246; Mahanthappa, M.K.; Bates, F.S.; Hillmyer, M.A., Macromolecules, 2005, 38 (19), 7890. Combining mechanistically incompatible monomers has not yet been exploited for the synthesis of PVOH-containing block copolymers.

[0005] Amphiphilic block copolymers and methods of preparation have been the subject of intensive research and development. Nonetheless, there remains a continuing need for well-defined block copolymers comprising PVOH and robust procedures for their preparation.

BRIEF SUMMARY OF EMB ODFMENT S OF THE INVENTION

[0006] One embodiment is a triblock copolymer having the structure

wherein Z is independently at each occurrence a polymer block comprising a poly( vinyl acetate), a poly(vinyl alcohol), or a poly(vinyl acetate-co-vinyl alcohol); A is a polyolefin block; L¹ is independently at each occurrence a group that is (-CH₂-)_X, wherein x is an integer from 1 to 10; L² is independently at each occurrence a C1-C12 alkylene group or C₆-C₁₂ arylene group; R¹ and R² are independently at each occurrence hydrogen, a C1-C12 alkylene group, a C6-C20 arylene group, a C1-C20 alkyloxy carbonyl group, or a cyano group; and y is independently at each occurrence 0 to 4. [0007] Another embodiment is a polymer membrane comprising the triblock copolymer.

0008] Another embodiment is a chain transfer agent having the structure

wherein L¹ is independently at each occurrence a group that is (-CH₂-)_X, wherein x is an integer from 1 to 10; L² is independently at each occurrence a C1-C12 alkylene group or C₆-Ci2 arylene group; R¹ and R² are independently at each occurrence hydrogen, a C1-C12 alkylene group, a C6-C20 arylene group, a C1-C20 acyl group, or a cyano group; y is independently at each occurrence 0 to 4; p is independently at each occurrence 0 or 1; X is independently at each occurrence - R⁵-, -0-, or -S-, wherein R⁵ is hydrogen, C1-C12 alkyl, C3-C12 cycloalkyl, C₆-Ci2 aryl, C2-20 alkenyl, C7-20 aralkyl, optionally substituted with one or more in-chain or pendent heteroatoms selected from the group consisting of oxygen, nitrogen, and sulfur; and R⁴ is independently at each occurrence C1-C20 alkyl, C3-C12 cycloalkyl, C₆- C20 aryl, C2-20 alkenyl, C7-20 aralkyl, or C2-7 acyl, optionally substituted with one or more in- chain or pendent heteroatoms selected from the group consisting of oxygen, nitrogen, and sulfur; provided that when X is -NR⁵-, R⁴ can optionally combine to form a ring with R⁵.

[0009] Another embodiment is a method of preparing the triblock copolymer, the method comprising polymerizing vinyl acetate in the presence of a chain transfer agent having he structure

wherein L¹ is independently at each occurrence a group that is (-CH₂-)_X, wherein x is an integer from 1 to 10; L² is independently at each occurrence a C1-C12 alkylene group or C₆-Ci2 arylene group; R¹ and R² are independently at each occurrence hydrogen, a C1-C12 alkylene group, a C6-C20 arylene group, a C1-C20 alkyloxy carbonyl group, or a cyano group; y is independently at each occurrence 0 to 4; p is independently at each occurrence 0 or 1; X is independently at each occurrence -NR⁵-, -0-, or -S-, wherein R⁵ is hydrogen, C1-C12 alkyl, C3-C12 cycloalkyl, C₆-Ci2 aryl, C2-20 alkenyl, C7-20 aralkyl, optionally substituted with one or more in-chain or pendent heteroatoms selected from the group consisting of oxygen, nitrogen, and sulfur; and R⁴ is independently at each occurrence C1-C20 alkyl, C3-C12 cycloalkyl, C₆- C20 aryl, C2-20 alkenyl, C7-20 aralkyl, or C2-7 acyl, optionally substituted with one or more in- chain or pendent heteroatoms selected from the group consisting of oxygen, nitrogen, and sulfur; provided that when X is -NR⁵-, R⁴ can optionally combine to form a ring with R⁵; to provide a macro-chain transfer agent comprising a poly(vinyl acetate); and polymerizing a cyclic olefin in the presence of the macro-chain transfer agent to provide the triblock copolymer.

0010] Another embodiment is polyolefin having the structure

wherein A is a polyolefin block; L¹ is independently at each occurrence a group that is (-CH₂- )x, wherein x is an integer from 1 to 10; L² is independently at each occurrence a C1-C12 alkylene group or C₆-Ci2 arylene group; R¹ and R² are independently at each occurrence hydrogen, a C1-C12 alkylene group, a C6-C20 arylene group, a C1-C20 alkyloxy carbonyl group, or a cyano group; y is independently at each occurrence 0 to 4; p is independently at each occurrence 0 or 1; X is independently at each occurrence -NR⁵-, -0-, or -S-, wherein R⁵ is hydrogen, C1-C12 alkyl, C3-C12 cycloalkyl, C₆-Ci2 aryl, C2-20 alkenyl, C7-20 aralkyl, optionally substituted with one or more in-chain or pendent heteroatoms selected from the group consisting of oxygen, nitrogen, and sulfur; and R⁴ is independently at each occurrence C1-C20 alkyl, C3-C12 cycloalkyl, C6-C20 aryl, C2-20 alkenyl, C7-20 aralkyl, or C2-7 acyl, optionally substituted with one or more in-chain or pendent heteroatoms selected from the group consisting of oxygen, nitrogen, and sulfur; provided that when X is -NR⁵-, R⁴ can optionally combine to form a ring with R⁵.

[0011] Another embodiment is a mid-functional polymer having the structure

wherein Z is independently at each occurrence a polymer block comprising a poly( vinyl acetate), a poly(vinyl alcohol), or a poly(vinyl acetate-co-vinyl alcohol); L¹ is independently at each occurrence a group that is (-CH₂-)_X, wherein x is an integer from 1 to 10; L² is independently at each occurrence a C1-C12 alkylene group or C₆-C₁₂ arylene group; R¹ and R² are independently at each occurrence hydrogen, a C1-C12 alkylene group, a C6-C20 arylene group, a C1-C20 alkyloxy carbonyl group, or a cyano group; y is independently at each occurrence 0 to 4; p is independently at each occurrence 0 or 1; X is independently at each occurrence - R⁵-, -0-, or -S-, wherein R⁵ is hydrogen, C1-C12 alkyl, C3-C12 cycloalkyl, C₆- C12 aryl, C2-20 alkenyl, C7-20 aralkyl, optionally substituted with one or more in-chain or pendent heteroatoms selected from the group consisting of oxygen, nitrogen, and sulfur; and R⁴ is independently at each occurrence C1-C20 alkyl, C3-C12 cycloalkyl, or C6-C20 aryl, C2-20 alkenyl, C7-20 aralkyl, or C2-7 acyl, optionally substituted with one or more in-chain or pendent heteroatoms selected from the group consisting of oxygen, nitrogen, and sulfur; provided that when X is -NR⁵-, R⁴ can optionally combine to form a ring with R⁵.

[0012] These and other embodiments are described in detail below.

BRIEF DESCRIPTION OF THE FIGURES

[0013] Figure 1 is a chemical scheme showing a synthetic route to a dixanthate chain transfer agent.

[0014] Figure 2 is a chemical scheme showing a synthetic route to a dixanthate- terminated poly(cyclooctene) by ROMP.

[0015] Figure 3 is a chemical scheme showing a synthetic route to a poly( vinyl acetate) having cis-2-butene functionality by RAFT polymerization.

[0016] Figure 4 is a chemical scheme showing a synthetic route to a poly( vinyl acetate)-£-polybutadiene-£-poly(vinyl acetate) triblock copolymer from a poly(vinyl acetate) macromolecular chain transfer agent.

[0017] Figure 5 shows insertion efficiency of the cyclic olefin monomer as a function of poly( vinyl acetate) number average molecular weight.

[0018] Figure 6 is a chemical scheme showing a synthetic route to a poly( vinyl alcohol)-£-polybutadiene-£-poly(vinyl alcohol).

DETAILED DESCRIPTION OF THE INVENTION

[0019] The present inventors have prepared triblock copolymers containing a polyolefin block and a poly( vinyl acetate) block, a poly(vinyl alcohol) block, or a poly( vinyl acetate-co-vinyl alcohol) block. The triblock copolymers can be prepared from a chain transfer agent having functionality capable of mediating both reversible addition- fragmentation transfer (RAFT) polymerizations and ring-opening metathesis polymerizations (ROMP). Also described are synthetic precursors to the triblock copolymer that include a mid-functional polymer and a chain end-functionalized polyolefin. The triblock copolymer and films prepared therefrom are useful in applications including separation of oil-water mixtures.

[0020] One aspect of the present disclosure is the chain transfer agent useful for forming the triblock copolymers. Thus, one embodiment is a chain transfer agent having the structure

wherein L¹ is independently at each occurrence a group that is (-CH₂-)_X, wherein x is an integer from 1 to 10; L² is independently at each occurrence a C1-C12 alkylene group or C₆-Ci2 arylene group; R¹ and R² are independently at each occurrence hydrogen, a C1-C12 alkylene group, a C6-C20 arylene group, a C1-C20 alkyloxy carbonyl group (-(CO)O-alkyl-), or a cyano group; y is independently at each occurrence 0 to 4; p is independently at each occurrence 0 or 1; X is independently at each occurrence - R⁵-, -0-, or -S-, wherein R⁵ is hydrogen, C1-C12 alkyl, C3-C12 cycloalkyl, C₆-Ci2 aryl, C2-20 alkenyl, C7-20 aralkyl, optionally substituted with one or more in-chain or pendent heteroatoms selected from the group consisting of oxygen, nitrogen, and sulfur; and R⁴ is independently at each occurrence C1-C20 alkyl, C3-C12 cycloalkyl, C6-C20 aryl, C2-20 alkenyl, C7-20 aralkyl, or C2-7 acyl, optionally substituted with one or more in-chain or pendent heteroatoms selected from the group consisting of oxygen, nitrogen, and sulfur; provided that when each occurrence of p is 1, and X is -NR⁵-, R⁴ can optionally combine to form a ring with R⁵. For example, in some embodiments, when X is -NR⁵-, R⁴ and R⁵ can combine to form a ring that is pyrrole, imidazole, piperidine, and the like. In some embodiments, p is 0, and R⁴ is preferably a Ci-6 alkyl group or a C₆-2o aryl group (e.g., a benzyl group). In some embodiments, each occurrence of L¹ is methylene (-CH₂-). In some embodiments, each occurrence of L² is

wherein n is independently at each occurrence 0, 1, 2, 3, or 4; and wherein R³ is

independently at each occurrence occurrence halogen, cyano, thiocyanato, nitro, C2-C12 alkylamido, C1-C12 alkyl, C1-C12 alkoxyl, C1-C12 alkylthio, C3-C12 cycloalkyl, C2-C12 acyl, C₆-Ci2 aryl, C3-C20 heteroaryl, or C1-C12 carbamoyl. In some embodiments, n is 0. In some embodiments, L¹ and L² are independently at each occurrence a divalent group (-L¹-, -L²-) in terms of their attachment to the rest of the compound. In some embodiments, each occurrence of R¹ and R² are hydrogen. In some embodiments, each occurrence of y is 1. In some embodiments, each occurrence of p is 1. In some embodiments, each occurrence of X is - H-, -0-, or -S-. In some embodiments, each occurrence of X is - H-, or -0-. In some embodiments, each occurrence of X is -0-. In some embodiments, each occurrence of R⁴ is ethyl. In an embodiment, each occurrence of L¹ is methylene (-CH₂-); each occurrence of L² is phenylene; each occurrence of y is 1; each occurrence of p is 1; each occurrence of X is - 0-; and each occurrence of R⁴ is ethyl.

[0021] In a specific embodiment, the chain transfer agent is a compound having the structure

wherein L is independently at each occurrence a group that is (-CH₂-)_X, wherein x is an integer from 1 to 10; n is independently at each occurrence 0, 1, 2, 3, or 4; R³ is

independently each occurrence halogen, cyano, thiocyanato, nitro, C₂-Ci₂ alkylamido, Ci-Ci₂ alkyl, Ci-Ci₂ alkoxyl, Ci-Ci₂ alkylthio, C₃-Ci₂ cycloalkyl, C₂-Ci₂ acyl, C₆-Ci₂ aryl, C₃-C₂o heteroaryl, or Ci-Ci₂ carbamoyl; X is independently at each occurrence - R⁵-, -0-, or -¾- wherein R⁵ is hydrogen, Ci-Ci₂ alkyl, C₃-Ci₂ cycloalkyl, or C₆-Ci₂ aryl; and R⁴ is

independently at each occurrence hydrogen, Ci-Ci₂ alkyl, C₃-Ci₂ cycloalkyl, C₆-Ci₂ aryl, C_2- i₂ alkenyl, C_7-13 alkylaryl, or C_2-7 acyl, optionally substituted with one or more in-chain or pendent heteroatoms selected from the group consisting of oxygen, nitrogen, and sulfur. In some embodiments, R⁴ is independently at each occurrence Ci-C₂₀ alkyl, C₃-Ci₂ cycloalkyl, or C₆-C₂o aryl, preferably alkyl, C₃-Ci₂ cycloalkyl, or C₆-Ci₂ aryl. In some embodiments, each occurrence of L¹ is methylene (-CH₂-). In some embodiments, L¹ is independently at each occurrence a divalent group (-L¹-) in terms of its attachment to the rest of the compound. In some embodiments, each occurrence of n is 0. In some embodiments, each occurrence of X is - H-, -0-, or -S-. In some embodiments, each occurrence of X is - NH-, or -0-. In some embodiments, each occurrence of X is -0-. In some embodiments, each occurrence of R⁴ is ethyl. In an embodiment, each occurrence of L¹ is methylene (-CH₂-); each occurrence of n is 0; each occurrence of X is -0-; and each occurrence of R⁴ is ethyl. In some embodiments, the chain transfer agent can be prepared by reacting 4-hydroxybenzyl alcohol with cis-l,4-dichloro-2-butene under basic conditions to form (Z)-l,4-bis(4- hydroxymethylphenoxy)but-2-ene, which is then reacted with a potassium salt of a xanthate ester or dithiocarbonate ester or trithiocarbonate ester to form the chain transfer agent.

[0022] The invention includes end-functionalized polyolefins formed using the above-described chain transfer agent. For example, the invention includes end-functionalized polyolefins having xanthate ester, dithiocarbonate ester, trithiocarbonate ester,

dithiocarbamate, or dithiobenzoate end groups. Thus, one embodiment is a polyolefin having the structure

wherein A is a polyolefin block; L¹ is independently at each occurrence a group that is (-CH₂- )x, wherein x is an integer from 1 to 10; L² is independently at each occurrence a C1-C12 alkylene group or C₆-Ci2 arylene group; R¹ and R² are independently at each occurrence hydrogen, a C1-C12 alkylene group, a C6-C20 arylene group, a C1-C20 alkyloxy carbonyl group, or a cyano group; y is independently at each occurrence 0 to 4; p is independently at each occurrence 0 or 1; X is independently at each occurrence - R⁵-, -0-, or -S-, wherein R⁵ is hydrogen, C1-C12 alkyl, C3-C12 cycloalkyl, C₆-Ci2 aryl, C2-20 alkenyl, C7-20 aralkyl, optionally substituted with one or more in-chain or pendent heteroatoms selected from the group consisting of oxygen, nitrogen, and sulfur; and R⁴ is independently at each occurrence C1-C20 alkyl, C3-C12 cycloalkyl, C6-C20 aryl, C2-20 alkenyl, C7-20 aralkyl, or C2-7 acyl, optionally substituted with one or more in-chain or pendent heteroatoms selected from the group consisting of oxygen, nitrogen, and sulfur; provided that when X is -NR⁵-, R⁴ can optionally combine to form a ring with R⁵. In some embodiments, each occurrence of y is 1. In some embodiments, each occurrence of p is 1. In some embodiments, L¹ and L² are independently at each occurrence a divalent group (-L¹-, -L²-) in terms of their attachment to the rest of the compound. In some embodiments, the polyolefin is a polybutadiene, a polycyclooctene, a polycyclooctadiene, a poly acetylene, a polynorbornene, a polyolefin derived from a functionalized norbornene, a polyolefin derived from a functionalized cyclooctene, a polyolefin derived from a functionalized cyclooctadiene, or a combination thereof. In some embodiments, when the polyolefin includes polybutadiene, the polybutadiene can be derived from 1,5-cyclooctadiene (i.e., by ring opening metathesis polymerization). In some embodiments, the polyolefin block excludes polybutadiene. In some embodiments, the polyolefin block is a divalent polyolefin block (-A-) in terms of its attachment to the rest of the compound. In some embodiments, each occurrence of L¹ is methylene (-CH₂-). In some embodiments, each occurrence of L² is

wherein n is independently at each occurrence 0, 1, 2, 3, or 4; and wherein R³ is independently at each occurrence occurrence halogen, cyano, thiocyanato, nitro, C₂-Ci₂ alkylamido,

alkyl,

alkoxyl, alkylthio, C -Ci₂ cycloalkyl, C₂-Ci₂ acyl, C₆-Ci₂ aryl, C -C₂₀ heteroaryl, or Ci-Ci₂ carbamoyl. In some embodiments, n is 0. In some embodiments, L¹ and L² are independently at each occurrence a divalent group (-L¹-, -L²-) in terms of their attachment to the rest of the compound. In some embodiments, each occurrence of R¹ and R² are hydrogen. In some embodiments, each occurrence ofR⁴ is ethyl. In some embodiments, each occurrence of p is 1. In some embodiments, each occurrence of X is - H-, -0-, or -S-. In some embodiments, each occurrence of X is -NH-, or -0-. In some embodiments, each occurrence of X is -0-. In some embodiments, the polyolefin is a polybutadiene, each occurrence of L¹ is methylene (-CH₂-); each occurrence of L² is phenylene; each occurrence of R¹ and R² are hydrogen; each occurrence of y is 1; each occurrence of p is 1; each occurrence of X is -0-; and each occurrence ofR⁴ is ethyl. In some embodiments, the polyolefin is a polycyclooctene, each occurrence of L¹ is methylene (-CH₂-); each occurrence of L² is phenylene; each occurrence ofR¹ and R² are hydrogen; each occurrence of y is 1 ; each occurrence of p is 1; each occurrence of X is -0-; and each occurrence ofR⁴ is ethyl.

0023] In an embodiment, the polyolefin has the structure

wherein A is a polyolefin block; L¹ is independently at each occurrence a group that is (-CH₂- )_x, wherein x is an integer from 1 to 10; n is independently at each occurrence 0, 1, 2, 3, or 4; R³ is independently at each occurrence halogen, cyano, thiocyanato, nitro, C₂-Ci₂ alkylamido, Ci-Ci₂ alkyl,

alkoxyl, alkylthio, C -Ci₂ cycloalkyl, C₂-Ci₂ acyl, C₆-Ci₂ aryl, C -C₂o heteroaryl, or

carbamoyl; X is independently at each occurrence - R⁵-, -0-, or -S-, wherein R⁵ is hydrogen, C1-C12 alkyl, C3-C12 cycloalkyl, or C₆-Ci2 aryl; and R⁴ is independently at each occurrence hydrogen, C1-C20 alkyl, C3-C12 cycloalkyl, C6-C20 aryl, C_2- 20 alkenyl, C7-20 alkylaryl, or C2-7 acyl, optionally substituted with one or more in-chain or pendent heteroatoms selected from the group consisting of oxygen, nitrogen, and sulfur. In some embodiments, R⁴ is independently at each occurrence C1-C20 alkyl, C3-C12 cycloalkyl, or C6-C20 aryl, preferably C1-C12 alkyl, C3-C12 cycloalkyl, or C₆-Ci2 aryl. As described above, the polyolefin can be a polybutadiene, a polycyclooctene, a polycyclooctadiene, a polynorbornene, a polyolefin derived from a functionalized norbornene, a polyacetylene, or a combination thereof. In some embodiments, the polyolefin block excludes polybutadiene. In some embodiments, the polyolefin is a divalent polyolefin (-A-) in terms of its attachment to the rest of the compound. In some embodiments, each occurrence of L¹ is methylene (-CH₂-). In some embodiments, each occurrence of n is 0. In some embodiments, each occurrence ofR⁴ is ethyl. In some embodiments, each occurrence of X is - H-, -0-, or -S-. In some embodiments, each occurrence of X is - H- or -0-. In some embodiments, each occurrence of X is -0-. In some embodiments, the polyolefin is a polybutadiene; each occurrence of L is methylene (-CH₂-); each occurrence of n is 0; each occurrence of X is -0-; and each occurrence ofR⁴ is ethyl. In some embodiments, the polyolefin is a

polycyclooctene; each occurrence of L is methylene (-CH₂-); each occurrence of n is 0; each occurrence of X is -0-; and each occurrence ofR⁴ is ethyl.

[0024] In some embodiments, the polyolefin can have a molecular weight of about 1,000 to about 500,000 Daltons (Da), for example about 1,000 to about 100,000 Da, for example about 1,000 to about 50,000 Da, for example about 1,000 to about 25,000 Da, for example about 1,000 to about 10,000 Da. In some embodiments, the polyolefin is a ring opening metathesis polymer. For example, the polyolefin can be the product of ring opening metathesis polymerization of a cyclic olefin. The end-functionalized polyolefin can be formed by reaction of the chain transfer agent with a cyclic olefin monomer (e.g., cyclooctene, cyclooctadiene, cyclooctatetraene, cyclopentadiene, dicyclopentadiene, norbornene, and the like) in the presence of a ROMP catalyst such as a ruthenium-containing catalyst. An example of such a procedure is described in the working examples below.

[0025] In some embodiments, the polyolefin includes in-chain aliphatic unsaturation. In some embodiments, the polyolefin can be at least partially hydrogenated. For example, a hydrogenated polyolefin can include less than or equal to 30% in-chain aliphatic

unsaturation, for example less than or equal to 20% in-chain aliphatic unsaturation, for example less than or equal to 10% in-chain aliphatic unsaturation, for example less than or equal to 5% in-chain aliphatic unsaturation, for example less than or equal to 1% in-chain aliphatic unsaturation. In some embodiments, a hydrogenated polyolefin is devoid of in- chain aliphatic unsaturation. Hydrogenation of a polyolefin can be carried out according to methods which are generally known. The degree of in-chain aliphatic unsaturation can be evaluated by a variety of methods, for example infrared spectroscopy and 1H and ¹ C nuclear magnetic resonance spectroscopy

[0026] The invention includes a mid-functional polymer formed using the above- described chain transfer agent. As used herein, the term "mid-functional" generally describes a polymer having a reactive functional group incorporated mid-chain, for example between two polymer blocks, wherein the polymer blocks can be the same or different. For example, the invention includes a mid-functional polymer having a cis-alkene functionality. Thus, one embodiment is a mid-functional polymer having the structure

wherein Z is independently at each occurrence a polymer block comprising a poly( vinyl acetate), a poly(vinyl alcohol), or a poly(vinyl acetate-co-vinyl alcohol); L¹ is independently at each occurrence a group that is (-CH₂-)_X, wherein x is an integer from 1 to 10; L² is independently at each occurrence a divalent C1-C12 alkylene group or C₆-Ci2 arylene group; R¹ and R² are independently at each occurrence hydrogen, a C1-C12 alkylene group, a C6-C20 arylene group, a C1-C20 alkyloxy carbonyl group, or a cyano group; y is independently at each occurrence 0 to 4; p is independently at each occurrence 0 or 1; X is independently at each occurrence - R⁵-, -0-, or -S-, wherein R⁵ is hydrogen, C1-C12 alkyl, C3-C12 cycloalkyl, C₆- C12 aryl, C2-20 alkenyl, C7-20 aralkyl, optionally substituted with one or more in-chain or pendent heteroatoms selected from the group consisting of oxygen, nitrogen, and sulfur; and R⁴ is independently at each occurrence C1-C20 alkyl, C3-C12 cycloalkyl, or C6-C20 aryl, C2-20 alkenyl, C7-20 aralkyl, or C2-7 acyl, optionally substituted with one or more in-chain or pendent heteroatoms selected from the group consisting of oxygen, nitrogen, and sulfur; provided that when X is -NR⁵-, R⁴ can optionally combine to form a ring with R⁵. For example, R⁴ and R⁵ can combine to form a ring that is pyrrole, imidazole, piperidine, and the like. In some embodiments, each occurrence of p is 0, and R⁴ is preferably a Ci-6 alkyl group or a C₆-2o aryl group (e.g., a benzyl group). In some embodiments, each occurrence of Z is a poly(vinyl alcohol). In some embodiments, each occurrence of Z is a poly(vinyl acetate). In some embodiments, each occurrence of Z is a poly(vinyl acetate-co-vinyl alcohol). In some embodiments, each occurrence of Z is a monovalent polymer block (-Z) in terms of its attachment to the rest of the compound. In some embodiments, each occurrence of L¹ is methylene (-CH₂-). In some embodiments, each occurrence of L² is

independently at each occurrence halogen, cyano, thiocyanato, nitro, C₂-Ci₂ alkylamido, Ci- Ci₂ alkyl, Ci-Ci₂ alkoxyl, Ci-Ci₂ alkylthio, C -Ci₂ cycloalkyl, C₂-Ci₂ acyl, C₆-Ci₂ aryl, C -C₂o heteroaryl, or Ci-Ci₂ carbamoyl. In some embodiments, n is 0. In some

embodiments, L¹ and L² are independently at each occurrence a divalent group (-L¹-, -L²-) in terms of their attachment to the rest of the compound. In some embodiments, each occurrence of R¹ and R² are hydrogen. In some embodiments, each occurrence of y is 1. In some embodiments, each occurrence of p is 1. In some embodiments, each occurrence of R⁴ is ethyl. In some embodiments, each occurrence of X is - H-, -0-, or -S-. In some embodiments, each occurrence of X is - H-, or -0-. In some embodiments, each occurrence of X is -0-. In some embodiments, each occurrence of Z is a poly(vinyl acetate), a poly(vinyl alcohol), or a poly( vinyl acetate-co-vinyl alcohol); each occurrence of L¹ is methylene (-CH₂- ); each occurrence of L² is phenylene; each occurrence of R¹ and R² are hydrogen; each occurrence of y is 1; each occurrence of p is 1; each occurrence of X is -0-; and each occurrence of R⁴ is ethyl.

[0027] In an embodiment, the mid-functional polymer has the structure

wherein Z is independently at each occurrence a polymer comprising a poly(vinyl acetate), a poly(vinyl alcohol), or a poly(vinyl acetate-co-vinyl alcohol); L¹ is independently at each occurrence a divalent group that is (-CH₂-)_X, wherein x is an integer from 1 to 10; n is independently at each occurrence 0, 1, 2, 3, or 4; R³ is independently at each occurrence halogen, cyano, thiocyanato, nitro, C₂-Ci₂ alkylamido, Ci-Ci₂ alkyl, Ci-Ci₂ alkoxyl, Ci-Ci₂ alkylthio, C -Ci₂ cycloalkyl, C₂-Ci₂ acyl, C₆-Ci₂ aryl, C -C₂₀ heteroaryl, or Ci-Ci₂ carbamoyl; X is independently at each occurrence - R⁵-, -0-, or -S-, wherein R⁵ is hydrogen, C1-C12 alkyl, C3-C12 cycloalkyl, or C₆-Ci2 aryl; and R⁴ is independently at each occurrence hydrogen, C1-C20 alkyl, C3-C12 cycloalkyl, C₆-C₂o aryl, C2-20 alkenyl, C7-20 alkylaryl, or C2-7 acyl, optionally substituted with one or more. In some embodiments, R⁴ is independently at each occurrence C1-C20 alkyl, C3-C12 cycloalkyl, or C6-C20 aryl, preferably C1-C12 alkyl, C₃- C12 cycloalkyl, or C₆-Ci2 aryl. In some embodiments, each occurrence of Z is a monovalent polymer block (-Z), for example a monovalent poly(vinyl alcohol), a monovalent poly( vinyl acetate), a monovalent poly( vinyl acetate-co-vinyl alcohol), or a combination thereof. The mid-functional polymer can have a molecular weight of about 200 to about 500,000 Daltons (Da), for example about 1,000 to about 100,000 Da, for example about 1,000 to about 50,000 Da, for example about 1,000 to about 25,000 Da, for example about 1,000 to about 15,000 Da. In some embodiments, the mid-functional polymer can have a dispersity of 1.05 to 2.0, for example 1.05 to 1.3. In some embodiments, each occurrence of L¹ is methylene (-CH₂-). In some embodiments, each occurrence of n is 0. In some embodiments, each occurrence of X is -NH-, -0-, or -S-. In some embodiments, each occurrence of X is - H- or -0-. In some embodiments, each occurrence of X is -0-. In some embodiments, each occurrence of R⁴ is ethyl. In some embodiments, each occurrence of Z is a poly( vinyl acetate); each occurrence of L¹ is methylene (-CH₂-); each occurrence of n is 0; each occurrence of X is -0-; and each occurrence ofR⁴ is ethyl. In some embodiments, each occurrence of Z is a monovalent poly( vinyl alcohol); each occurrence of L¹ is methylene (-CH₂-); each occurrence of n is 0; each occurrence of X is -0-; and each occurrence ofR⁴ is ethyl. In some embodiments, each occurrence of Z is a poly(vinyl acetate-co-vinyl alcohol); each occurrence of L¹ is methylene (-CH₂-); each occurrence of n is 0; each occurrence of X is -0-; and each occurrence of R⁴ is ethyl. The mid-functional polymer can be formed by reaction of the above-described chain transfer agent with vinyl acetate in the presence of a radical source such as

azobisisobutyronitrile (AIBN). An example of such a procedure is described in the working examples below.

[0028] The invention includes a triblock copolymer comprising a polyolefin block and a poly(vinyl acetate), a poly(vinyl alcohol), or a poly( vinyl acetate-co-vinyl alcohol). In some embodiments, a poly(vinyl alcohol) can comprise repeat units derived from vinyl acetate due to incomplete hydrolysis. For example, a poly(vinyl alcohol) can comprise less than or equal to 20 mole percent vinyl acetate, or less than or equal to 10 mole percent vinyl acetate, or less than or equal to 5 mole percent vinyl acetate, or less than or equal to 1 mole percent vinyl acetate, based on the total moles of the poly( vinyl alcohol). The relative amounts of vinyl acetate and vinyl alcohol can be evaluated by a variety of methods, for example infrared spectroscopy and 1H and ¹ C nuclear magnetic resonance spectroscopy.

[0029] Thus, one embodiment is a triblock copolymer having the structure

wherein Z is independently at each occurrence a polymer block comprising a poly( vinyl acetate), a poly(vinyl alcohol), or a poly(vinyl acetate-co-vinyl alcohol); A is a polyolefin block; L¹ is independently at each occurrence a group that is (-CH₂-)_X, wherein x is an integer from 1 to 10; L² is independently at each occurrence a C₁-C₁₂ alkylene group or C₆-Ci₂ arylene group; R¹ and R² are independently at each occurrence hydrogen, a C₁-C₁₂ alkylene group, a C6-C20 arylene group, a C1-C20 alkyloxy carbonyl group, or a cyano group; and y is independently at each occurrence 0 to 4. In some embodiments, each occurrence of Z is a poly(vinyl acetate). In some embodiments, each occurrence of Z is a poly(vinyl alcohol). In some embodiments, each occurrence of Z is a poly (vinyl acetate-co-vinyl alcohol). In some embodiments, each occurrence of Z is a monovalent polymer block (-Z) in terms of its attachment to the rest of the compound. In some embodiments, the polyolefin is a polybutadiene, a polycyclooctene, a polycyclooctadiene, a polyacetylene, a polynorbornene, a polyolefin derived from a functionalized norbornene, a polyolefin derived from a

functionalized cyclooctene, a polyolefin derived from a functionalized cyclooctadiene, or a combination thereof. In some embodiments, the polyolefin block excludes polybutadiene. In some embodiments, the polyolefin block is a divalent polyolefin block (-A-) in terms of its attachment to the rest of the compound. In some embodiments, L¹ and L² are independently at each occurrence a divalent group (-L¹-, -L²-) in terms of their attachment to the rest of the compound. In some embodiments, each occurrence of L¹ is methylene (-CH₂-). In some embodiments, each occurrence of L² is

wherein n is independently at each occurrence 0, 1, 2, 3, or 4; and wherein R³ is independently at each occurrence occurrence halogen, cyano, thiocyanato, nitro, C₂-C₁₂ alkylamido, C₁-C₁₂ alkyl, C1-C12 alkoxyl, C1-C12 alkylthio, C3-C12 cycloalkyl, C2-C12 acyl, C₆-Ci2 aryl, C3-C20 heteroaryl, or C₁-C₁₂ carbamoyl. In some embodiments, n is 0. In some embodiments, each occurrence of R¹ and R² are hydrogen. In some embodiments, each occurrence of y is 1. [0030] In an embodiment, the triblock copolymer has the structure

wherein Z is independently at each occurrence a polymer block comprising a poly( vinyl acetate), a poly(vinyl alcohol), or a poly(vinyl acetate-co-vinyl alcohol); A is a polyolefin block; L¹ is independently at each occurrence a group that is (-CH₂-)_X, wherein x is an integer from 1 to 10; n is independently at each occurrence of 0, 1, 2, 3, or 4; and R³ is independently at each occurrence halogen, cyano, thiocyanato, nitro, C₂-Ci₂ alkylamido,

alkyl, Ci- C₁₂ alkoxyl, Ci-Ci₂ alkylthio, C -Ci₂ cycloalkyl, C₂-Ci₂ acyl, C₆-Ci₂ aryl, C -C₂₀ heteroaryl, or Ci-Ci₂ carbamoyl. In some embodiments, each occurrence of Z is a poly(vinyl alcohol), a poly(vinyl acetate), or a poly(vinyl acetate-co-vinyl alcohol). In some embodiments, the polyolefin is a polybutadiene, a polycyclooctene, a polycyclooctadiene, a polynorbornene, a polyolefin derived from a functionalized norbornene, a polyacetylene, or a combination thereof. In some embodiments, each occurrence of L¹ is methylene (-CH₂-). In some embodiments, each occurrence of n is 0. In an embodiment, each occurrence of Z is a poly(vinyl acetate); A is a polybutadiene; each occurrence of L¹ is methylene (-CH₂-); and each occurrence of n is 0. In an embodiment, each occurrence of Z is a poly(vinyl alcohol); A is a polybutadiene; each occurrence of L¹ is methylene (-CH₂-); and each occurrence of n is 0. In an embodiment, each occurrence of Z is a poly(vinyl acetate-co-vinyl alcohol); A is a polybutadiene; each occurrence of L¹ is methylene (-CH₂-); and each occurrence of n is 0. In an embodiment, each occurrence of Z is a poly(vinyl acetate); A is a polycyclooctene; each occurrence of L¹ is methylene (-CH₂-); and each occurrence of n is 0. In an embodiment, each occurrence of Z is a poly(vinyl alcohol); A is a polycyclooctene; each occurrence of L¹ is methylene (-CH₂-); and each occurrence of n is 0. In an embodiment, each occurrence of Z is a poly(vinyl acetate-co-vinyl alcohol); A is a divalent polycyclooctene; each occurrence of L¹ is methylene (-CH₂-); and each occurrence of n is 0.

[0031] In some embodiments, the triblock copolymer has a number average molecular weight of about 1,000 to about 1,000,000 Da, for example about 5,000 to about 100,000 Da, for example about 5,000 to about 40,000 Da, and a dispersity of about 1.3 to about 3.0, for example about 1.3 to about 1.8.

[0032] Another aspect of the invention is a method for producing the triblock copolymers. The triblock copolymer can be formed by sequential ROMP and RAFT polymerizations. Thus, in an embodiment, the method of preparing the triblock copolymer comprises polymerizing vinyl acetate in the presence of the above-described chain transfer agent to provide a macro-chain transfer agent comprising the mid-functional polymer disclosed herein, and polymerizing a cyclic olefin in the presence of the mid-functional polymer. The polymerizing of the vinyl acetate can be, for example, by RAFT in the presence of a radical source (e.g., AIBN). The polymerizing of the cyclic olefin can be by ROMP in the presence of a suitable ROMP catalyst, for example a ruthenium-containing catalyst. In some embodiments, the method further comprises hydrolyzing the poly(vinyl acetate)-containing triblock copolymer to provide a poly( vinyl alcohol) or a poly( vinyl acetate-co-vinyl alcohol)-containing triblock copolymer. An exemplary synthesis of a triblock copolymer is detailed in the working examples below.

[0033] Triblock copolymers comprising a poly(vinyl alcohol) block are formed by hydrolysis of the corresponding poly(vinyl acetate) copolymer. In the working examples below, this reaction is described in detail for embodiments in which the triblock copolymer is a poly( vinyl acetate)-£-polybutadiene-£-poly( vinyl acetate) triblock copolymer. The same techniques are also applicable to embodiments in which the polyolefin block is a polyolefin other than poly(butadiene).

[0034] The triblock copolymer is useful for forming structures including polymer films. The formation of a polymer film is described in the working examples. Films formed from the triblock copolymer typically have a thickness of about 10 to about 100 micrometers, specifically about 20 to about 80 micrometers. In some embodiments, the film can have a thickness corresponding to about one period of the block copolymer. The relationship between film thickness and the period of the block copolymer can be determined using methods known in the art. See, for example, Russell, T. P.; Lambooy, P.; Barker, J. G.; Gallagher, P. D.; Satija, S. K.; Kellogg, G. J.; and A. M. Mayes, Macromolecules, 1995, 28, 787; and Mayes, A. M.; and Kumar, S. K., MRS Bulletin, 1997, 22, 43. Block copolymer films can be thermally annealed and/or solvent vapor annealed to yield highly ordered structures.

[0035] In some embodiments, a film can be formed from a triblock copolymer comprising a poly(vinyl acetate) block. The film can be subjected to the hydrolysis conditions described above, and the poly(vinyl acetate) block can be hydrolyzed to provide a film comprising the triblock copolymer having the corresponding poly(vinyl alcohol) block or the corresponding poly(vinyl acetate-co-vinyl alcohol) block.

[0036] The invention includes at least the following embodiments. [0037] Embodiment 1 : A triblock copolymer having the structure

wherein Z is independently at each occurrence a polymer block comprising a poly( vinyl acetate), a poly(vinyl alcohol), or a poly(vinyl acetate-co-vinyl alcohol); A is a polyolefin block; L¹ is independently at each occurrence a group that is (-CH₂-)_X, wherein x is an integer from 1 to 10; L² is independently at each occurrence a C1-C12 alkylene group or C₆-Ci2 arylene group; R¹ and R² are independently at each occurrence hydrogen, a C1-C12 alkylene group, a C6-C20 arylene group, a C1-C20 alkyloxy carbonyl group, or a cyano group; and y is independently at each occurrence 0 to 4.

0038] Embodiment la: A triblock copolymer having the structure

wherein Z is independently at each occurrence a polymer block comprising a poly( vinyl acetate), a poly(vinyl alcohol), or a poly(vinyl acetate-co-vinyl alcohol); A is a polyolefin block; L¹ is independently at each occurrence a group that is (-CH₂-)_X, wherein x is an integer from 1 to 10; n is independently at each occurrence of 0, 1, 2, 3, or 4; and R³ is independently at each occurrence halogen, cyano, thiocyanato, nitro, C2-C12 alkylamido, C1-C12 alkyl, Ci- C12 alkoxyl, C1-C12 alkylthio, C3-C12 cycloalkyl, C2-C12 acyl, C₆-Ci2 aryl, C3-C20 heteroaryl, or C1-C12 carbamoyl.

[0039] Embodiment 2: The triblock copolymer of embodiment 1 or la, wherein each occurrence of Z is a poly(vinyl alcohol).

[0040] Embodiment 3 : The triblock copolymer of embodiment 1 or 1 a, wherein each occurrence of Z is a poly(vinyl acetate).

[0041] Embodiment 4: The triblock copolymer of embodiment 1 or la, wherein each occurrence of Z is a poly(vinyl acetate-co- vinyl alcohol).

[0042] Embodiment 5: The triblock copolymer of any one of embodiments 1 to 4, wherein the polyolefin is a polybutadiene.

[0043] Embodiment 6: The triblock copolymer of any one of embodiments 1 to 4, wherein the polyolefin is a polycyclooctene.

[0044] Embodiment 7: The triblock copolymer of any one of embodiments 1 to 6, wherein each occurrence of L¹ is methylene (-CH₂-).

[0045] Embodiment 8: The triblock copolymer of any one of embodiments 1 or 2 to

7, wherein each occurrence of L² is

independently at each occurrence occurrence halogen, cyano, thiocyanato, nitro, C₂-Ci₂ alkylamido, Ci-Ci₂ alkyl,

alkoxyl, alkylthio, C -Ci₂ cycloalkyl, C₂-Ci₂ acyl, C₆-Ci₂ aryl, C -C₂₀ heteroaryl, or Ci-Ci₂ carbamoyl.

[0046] Embodiment 9: The triblock copolymer of embodiments la to 8, wherein each occurrence of n is 0.

[0047] Embodiment 10: The triblock copolymer of any one of embodiments 1 or 2 to 9, wherein each occurrence of R¹ and R² are hydrogen and each occurrence of y is 1.

[0048] Embodiment 11 : The triblock copolymer of embodiment 1, wherein each occurrence of Z is a poly( vinyl acetate); A is a polybutadiene; each occurrence of L¹ is methylene (-CH₂-); each occurrence of L² is phenylene; each occurrence of R¹ and R² are hydrogen and each occurrence of y is 1.

[0049] Embodiment 12: The triblock copolymer of embodiment 1, wherein each occurrence of Z is a monovalent poly( vinyl alcohol); A is a polybutadiene; each occurrence of L¹ is methylene (-CH₂-); each occurrence of L² is phenylene; each occurrence of R¹ and R² are hydrogen and each occurrence of y is 1.

[0050] Embodiment 13 : The triblock copolymer of embodiment 1, wherein each occurrence of Z is a poly( vinyl acetate); A is a poly(cyclooctene); each occurrence of L¹ is methylene (-CH₂-); each occurrence of L² is phenylene; each occurrence of R¹ and R² are hydrogen and each occurrence of y is 1.

[0051] Embodiment 14: The triblock copolymer of embodiment 1, wherein each occurrence of Z is a poly(vinyl alcohol); A is a poly(cyclooctene); each occurrence of L¹ is methylene (-CH₂-); each occurrence of L² is phenylene; each occurrence of R¹ and R² are hydrogen and each occurrence of y is 1.

[0052] Embodiment 15: The triblock copolymer of embodiment 1, wherein each occurrence of Z is a poly(vinyl acetate-co vinyl alcohol); A is a polybutadiene; each occurrence of L¹ is methylene (-CH₂-); each occurrence of L² is phenylene; each occurrence of R¹ and R² are hydrogen and each occurrence of y is 1.

[0053] Embodiment 16: The triblock copolymer of embodiment 1, wherein each occurrence of Z is a poly(vinyl acetate-co vinyl alcohol); A is a poly(cyclooctene); each occurrence of L¹ is methylene (-CH₂-); each occurrence of L² is phenylene; each occurrence of R¹ and R² are hydrogen and each occurrence of y is 1.

0054] Embodiment 17: A polyolefin having the structure

wherein A is a polyolefin block; L¹ is independently at each occurrence a group that is (-CH₂- )x, wherein x is an integer from 1 to 10; L² is independently at each occurrence a Ci-Ci₂ alkylene group or C₆-Ci₂ arylene group; R¹ and R² are independently at each occurrence hydrogen, a alkylene group, a C₆-C₂o arylene group, a Ci-C₂₀ alkyloxy carbonyl group, or a cyano group; y is independently at each occurrence 0 to 4; p is independently at each occurrence 0 or 1; X is independently at each occurrence -NR⁵-, -0-, or -S-, wherein R⁵ is hydrogen, alkyl, C -Ci₂ cycloalkyl, C₆-Ci₂ aryl, C_2-2o alkenyl, C_7-2o aralkyl, optionally substituted with one or more in-chain or pendent heteroatoms selected from the group consisting of oxygen, nitrogen, and sulfur; and R⁴ is independently at each occurrence Ci-C₂₀ alkyl, C -Ci₂ cycloalkyl, C₆-C₂o aryl, C_2-2o alkenyl, C_7-2o aralkyl, or C_2-7 acyl, optionally substituted with one or more in-chain or pendent heteroatoms selected from the group consisting of oxygen, nitrogen, and sulfur; provided that when X is -NR⁵-, R⁴ can optionally combine to form a ring with R⁵.

0055] Embodiment 17a: A polyolefin having the structure

wherein A is a polyolefin block; L¹ is independently at each occurrence a group that is (-CH₂- )x, wherein x is an integer from 1 to 10; n is independently at each occurrence 0, 1, 2, 3, or 4; R³ is independently at each occurrence halogen, cyano, thiocyanato, nitro, C₂-Ci₂ alkylamido, Ci-Ci₂ alkyl,

alkoxyl, alkylthio, C -Ci₂ cycloalkyl, C₂-Ci₂ acyl, C₆-Ci₂ aryl, C3-C20 heteroaryl, or C1-C12 carbamoyl; X is independently at each occurrence - R⁵-, -0-, or -S-, wherein R⁵ is hydrogen, C1-C12 alkyl, C3-C12 cycloalkyl, or C₆-Ci2 aryl; and R⁴ is independently at each occurrence hydrogen, C1-C20 alkyl, C3-C12 cycloalkyl, C6-C20 aryl, C2- 20 alkenyl, C7-20 alkylaryl, or C2-7 acyl, optionally substituted with one or more in-chain or pendent heteroatoms selected from the group consisting of oxygen, nitrogen, and sulfur.

[0056] Embodiment 18: The polyolefin of embodiment 17 or 17a, wherein the polyolefin is a poly(butadiene).

[0057] Embodiment 19: The polyolefin of embodiment 17 or 17 a, wherein the polyolefin is a poly(cyclooctene).

[0058] Embodiment 20: The polyolefin of any one of embodiments 17 to 19, wherein each occurrence of L¹ is methylene (-CH₂-).

[0059] Embodiment 21 : The polyolefin of any one of embodiments 17 or 18 to 20, wherein L² is

independently at each occurrence occurrence halogen, cyano, thiocyanato, nitro, C2-C12 alkylamido, C1-C12 alkyl, C1-C12 alkoxyl, C1-C12 alkylthio, C3-C12 cycloalkyl, C2-C12 acyl, C₆-Ci2 aryl, C3-C20 heteroaryl, or C1-C12 carbamoyl.

[0060] Embodiment 22: The polyolefin of any one of embodiments 17 or 18 to 21, wherein each occurrence of R¹ and R² are hydrogen and each occurrence of y is 1.

[0061] Embodiment 23 : The polyolefin of any one of embodiments 17a or 21 to 22, wherein each occurrence of n is 0.

[0062] Embodiment 24: The polyolefin of any one of embodiments 17 to 23, wherein each occurrence of R⁴ is ethyl.

[0063] Embodiment 25: The polyolefin of any one of embodiments 17 to 24, wherein each occurrence of X is -NH- or -0-.

[0064] Embodiment 26: The polyolefin of any one of embodiments 17 to 25, wherein each occurrence of X is -0-.

[0065] Embodiment 27: The polyolefin of embodiment 17, wherein the polyolefin is a polybutadiene; each occurrence of L¹ is methylene (-CH₂-); each occurrence of L² is phenylene; each occurrence of R¹ and R² are hydrogen; each occurrence of y is 1; each occurrence of p is 1; each occurrence of X is -0-; and each occurrence of R⁴ is ethyl.

[0066] Embodiment 28: The polyolefin of embodiment 17, wherein the polyolefin is a polycyclooctene; each occurrence of L¹ is methylene (-CH₂-); each occurrence of L² is phenylene; each occurrence of R¹ and R² are hydrogen; each occurrence of y is 1; each occurrence of p is 1; each occurrence of X is -0-; and each occurrence of R⁴ is ethyl.

[0067] Embodiment 29: A mid-functional polymer having the structure

wherein Z is independently at each occurrence a polymer block comprising a poly( vinyl acetate), a poly(vinyl alcohol), or a poly(vinyl acetate-co-vinyl alcohol); L¹ is independently at each occurrence a group that is (-CH₂-)_X, wherein x is an integer from 1 to 10; L² is independently at each occurrence a C₁-C₁₂ alkylene group or C₆-Ci₂ arylene group; and R¹ and R² are independently at each occurrence hydrogen, a Ci-Ci₂ alkylene group, a C₆-C₂o arylene group, a Ci-C₂₀ alkyloxy carbonyl group, or a cyano group; y is independently at each occurrence 0 to 4; p is independently at each occurrence 0 or 1; X is independently at each occurrence - R⁵-, -0-, or -S-, wherein R⁵ is hydrogen, Ci-Ci₂ alkyl, C -Ci₂ cycloalkyl, C₆- C₁₂ aryl, C_2-2o alkenyl, C_7-2o aralkyl, optionally substituted with one or more in-chain or pendent heteroatoms selected from the group consisting of oxygen, nitrogen, and sulfur; and R⁴ is independently at each occurrence Ci-C₂₀ alkyl, C -Ci₂ cycloalkyl, C₆-C₂o aryl, C_2-2o alkenyl, C_7-2o aralkyl, or C_2-7 acyl, optionally substituted with one or more in-chain or pendent heteroatoms selected from the group consisting of oxygen, nitrogen, and sulfur; provided that when X is -NR⁵-, R⁴ can optionally combine to form a ring with R⁵.

[0068] Embodiment 29a: A mid-functional polymer having the structure

wherein Z is independently at each occurrence a polymer comprising a poly(vinyl acetate), a poly(vinyl alcohol), or a poly(vinyl acetate-co-vinyl alcohol); L¹ is independently at each occurrence a group that is (-CH₂-)_X, wherein x is an integer from 1 to 10; n is independently at each occurrence 0, 1, 2, 3, or 4; R³ is independently at each occurrence halogen, cyano, thiocyanato, nitro, C2-C12 alkylamido, C1-C12 alkyl, C1-C12 alkoxyl, C1-C12 alkylthio, C3-C12 cycloalkyl, C2-C12 acyl, C₆-Ci2 aryl, heteroaryl, or carbamoyl; X is independently at each occurrence - R⁵-, -0-, or -S-, wherein R⁵ is hydrogen, C1-C12 alkyl, C3-C12 cycloalkyl, or C₆-Ci2 aryl; and R⁴ is independently at each occurrence hydrogen, C1-C20 alkyl, C3-C12 cycloalkyl, C6-C20 aryl, C2-20 alkenyl, C7-20 alkylaryl, or C2-7 acyl, optionally substituted with one or more in-chain or pendent heteroatoms selected from the group consisting of oxygen, nitrogen, and sulfur.

[0069] Embodiment 30: The mid-functional polymer of embodiment 29 or 29a, wherein each occurrence of Z is a poly(vinyl alcohol).

[0070] Embodiment 31 : The mid-functional polymer of embodiment 29 or 29a, wherein each occurrence of Z is a poly(vinyl acetate).

[0071] Embodiment 32: The mid-functional polymer of embodiment 29 or 29a, wherein each occurrence of Z is a poly(vinyl acetate-co-vinyl alcohol).

[0072] Embodiment 33 : The mid-functional polymer of any one of embodiments 29 to 32, wherein each occurrence of L¹ is methylene (-CH₂-).

[0073] Embodiment 34: The mid- functional polymer of any one of embodiments 29 or 30 to 32 wherein L² is

[0074] Embodiment 35: The mid- functional polymer of any one of embodiments 29a or 34, wherein each occurrence of n is 0.

[0075] Embodiment 36: The mid-functional polymer of any of embodiments 29 or 30 to 35, wherein each occurrence of R¹ and R² are hydrogen and each occurrence of y is 1.

[0076] Embodiment 37: The mid- functional polymer of any one of embodiments 29 to 36, wherein each occurrence of X is - H- or -0-.

[0077] Embodiment 38: The mid- functional polymer of any one of embodiments 29 to 37, wherein each occurrence of X is -0-.

[0078] Embodiment 39: The mid- functional polymer of any one of embodiments 29 to 38, wherein each occurrence of R⁴ is ethyl.

[0079] Embodiment 40: The mid-functional polymer of embodiment 29, wherein each occurrence of Z is a poly(vinyl acetate); each occurrence of L¹ is methylene (-CH₂-); each occurrence of L² is phenylene; each occurrence of R¹ and R² are hydrogen; each occurrence of y is 1; each occurrence of p is 1; each occurrence of X is -0-; and each occurrence of R³ is ethyl.

[0080] Embodiment 41 : The mid-functional polymer of embodiment 29, wherein each occurrence of Z is a poly(vinyl alcohol); each occurrence of L¹ is methylene (-CH₂-); each occurrence of L² is phenylene; each occurrence of R¹ and R² are hydrogen; each occurrence of y is 1; each occurrence of p is 1; each occurrence of X is -0-; and each occurrence of R⁴ is ethyl.

[0081] Embodiment 42: The mid-functional polymer of embodiment 25, wherein each occurrence of Z is a poly(vinyl acetate-co vinyl alcohol); each occurrence of L¹ is methylene (-CH₂-); each occurrence of L² is phenylene; each occurrence of R¹ and R² are hydrogen; each occurrence of y is 1; each occurrence of p is 1; each occurrence of X is -0-; and each occurrence of R⁴ is ethyl.

0082] Embodiment 43 : A chain transfer agent having the structure

wherein L¹ is independently at each occurrence a group that is (-CH₂-)_X, wherein x is an integer from 1 to 10; L² is independently at each occurrence a Ci-Ci₂ alkylene group or C₆-Ci₂ arylene group; R¹ and R² are independently at each occurrence hydrogen, a Ci-Ci₂ alkylene group, a C₆-C₂o arylene group, a Ci-C₂₀ alkyloxy carbonyl group, or a cyano group; y is independently at each occurrence 0 to 4; p is independently at each occurrence 0 or 1; X is independently at each occurrence - R⁵-, -0-, or -S-, wherein R⁵ is hydrogen, Ci-Ci₂ alkyl, C₃-Ci₂ cycloalkyl, C₆-Ci₂ aryl, C_2-2o alkenyl, C_7-2o aralkyl, optionally substituted with one or more in-chain or pendent heteroatoms selected from the group consisting of oxygen, nitrogen, and sulfur; and R⁴ is independently at each occurrence Ci-C₂₀ alkyl, C -Ci₂ cycloalkyl, C₆- C₂o aryl, C_2-2o alkenyl, C_7-2o aralkyl, or C_2-7 acyl, optionally substituted with one or more in- chain or pendent heteroatoms selected from the group consisting of oxygen, nitrogen, and sulfur; provided that when X is -NR⁵-, R⁴ can optionally combine to form a ring with R⁵. 0083] Embodiment 43a: A chain transfer agent having the structure

wherein L¹ is independently at each occurrence a group that is (-CH₂-)_X, wherein x is an integer from 1 to 10; n is independently at each occurrence 0, 1, 2, 3, or 4; R³ is

independently each occurrence halogen, cyano, thiocyanato, nitro, C₂-Ci₂ alkylamido,

alkyl,

alkoxyl, alkylthio, C -Ci₂ cycloalkyl, C₂-Ci₂ acyl, C₆-Ci₂ aryl, C -C₂₀ heteroaryl, or Ci-Ci₂ carbamoyl; X is independently at each occurrence - R⁵-, -0-, or -¾- wherein R⁵ is hydrogen, Ci-Ci₂ alkyl, C -Ci₂ cycloalkyl, or C₆-Ci₂ aryl; and R⁴ is

independently at each occurrence hydrogen, Ci-C₂₀ alkyl, C -Ci₂ cycloalkyl, C₆-C₂o aryl, C_2- ₂o alkenyl, C_7-2o alkylaryl, or C_2-7 acyl, optionally substituted with one or more in-chain or pendent heteroatoms selected from the group consisting of oxygen, nitrogen, and sulfur.

[0084] Embodiment 44: The chain transfer agent of embodiment 43 or 43 a, wherein each occurrence of L¹ is methylene (-CH₂-).

0085] Embodiment 45: The chain transfer agent of embodiment 43, wherein L² is

independently at each occurrence occurrence halogen, cyano, thiocyanato, nitro, C₂-Ci₂ alkylamido, Ci-Ci₂ alkyl, Ci-Ci₂ alkoxyl, Ci-Ci₂ alkylthio, C -Ci₂ cycloalkyl, C₂-Ci₂ acyl, C₆-Ci₂ aryl, C -C₂₀ heteroaryl, or Ci-Ci₂ carbamoyl.

[0086] Embodiment 46: The chain transfer agent of embodiments 43 a or 45, wherein each occurrence of n is 0.

[0087] Embodiment 47: The chain transfer agent of any of embodiments 43 to 46, wherein each occurrence of X is - H- or -0-.

[0088] Embodiment 48: The chain transfer agent of any of embodiments 43 to 47, wherein each occurrence of X is -0-.

[0089] Embodiment 49: The chain transfer agent of any of embodiments 43 to 48, wherein each occurrence of R⁴ is ethyl.

[0090] Embodiment 50: The chain transfer agent of embodiment 43, wherein each occurrence of L¹ is methylene (-CH₂-); each occurrence of L² is phenylene; each occurrence of R¹ and R² are hydrogen; each occurrence of y is 1 ; each occurrence of p is 1 ; each occurrence of X is -0-; and each occurrence of R⁴ is ethyl.

[0091] Embodiment 51 : A polymer membrane comprising the triblock copolymer of any of embodiments 1 to 16.

[0092] Embodiment 52: A method of preparing the triblock copolymer of any of embodiments 1 to 16, the method comprising, polymerizing vinyl acetate in the presence of a chain tr nsfer agent having the structure

independently each occurrence halogen, cyano, thiocyanato, nitro, C₂-Ci₂ alkylamido, C_\-Cn alkyl, C_\-Cn alkoxyl, C_\-Cn alkylthio, C -Ci₂ cycloalkyl, C₂-Ci₂ acyl, C₆-Ci₂ aryl, C -C₂₀ heteroaryl, or Ci-Ci₂ carbamoyl; y is independently at each occurrence 0 or 1 ; p is independently at each occurrence 0 or 1 ; X is independently at each occurrence - R⁵-, -0-, or -S-, wherein R⁵ is hydrogen, Ci-Ci₂ alkyl, C -Ci₂ cycloalkyl, C₆-Ci₂ aryl, C_2-2o alkenyl, C_7-2o aralkyl, optionally substituted with one or more in-chain or pendent heteroatoms selected from the group consisting of oxygen, nitrogen, and sulfur; and R⁴ is independently at each occurrence Ci-C₂₀ alkyl, C -Ci₂ cycloalkyl, C₆-C₂o aryl, C_2-2o alkenyl, C_7-2o aralkyl, or C_2-7 acyl, optionally substituted with one or more in-chain or pendent heteroatoms selected from the group consisting of oxygen, nitrogen, and sulfur; provided that when X is -NR⁵-, R⁴ can optionally combine to form a ring with R⁵; to provide a macro-chain transfer agent comprising a poly(vinyl acetate); and polymerizing a cyclic olefin in the presence of the macro-chain transfer agent to provide the triblock copolymer.

[0093] Embodiment 53 : The method of embodiment 52, further comprising hydrolyzing the triblock copolymer to provide a triblock copolymer comprising poly( vinyl alcohol).

[0094] All cited patents, patent applications, and other references are incorporated herein by reference in their entirety, including U.S. priority application 62/183,408, filed June 23, 2015. However, if a term in the present application contradicts or conflicts with a term in the incorporated reference, the term from the present application takes precedence over the conflicting term from the incorporated reference.

[0095] All ranges disclosed herein are inclusive of the endpoints, and the endpoints are independently combinable with each other. Each range disclosed herein constitutes a disclosure of any point or sub-range lying within the disclosed range.

[0096] The use of the terms "a" and "an" and "the" and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. Further, it should further be noted that the terms "first," "second," and the like herein do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. The modifier "about" used in connection with a quantity is inclusive of the stated value and has the meaning dictated by the context (e.g., it includes the degree of error associated with measurement of the particular quantity).

[0097] As used herein, the term "alkyl" means a branched or straight chain, saturated, monovalent hydrocarbon group, e.g., methyl, ethyl, i-propyl, and n-butyl. "Alkylene" means a straight or branched chain, saturated, divalent hydrocarbon group (e.g., methylene (-CH₂-) or propylene (-(CH₂)3-)). "Alkenyl" and "alkenylene" mean a monovalent or divalent, respectively, straight or branched chain hydrocarbon group having at least one carbon-carbon double bond (e.g., ethenyl (-HC=CH₂) or propenylene (-HC(CH₃)=CH₂-). "Alkynyl" means a straight or branched chain, monovalent hydrocarbon group having at least one carbon- carbon triple bond (e.g., ethynyl). "Alkoxy" means an alkyl group linked via an oxygen (i.e., alkyl-O-), for example methoxy, ethoxy, and sec-butyloxy. "Cycloalkyl" and

"cycloalkylene" mean a monovalent and divalent cyclic hydrocarbon group, respectively, of the formula -C_nH_2n-x and -C_nH_2n-2x- wherein x is the number of cyclization(s). "Aryl" means a monovalent, monocyclic or polycyclic aromatic group (e.g., phenyl or naphthyl).

"Arylene" means a divalent, monocyclic or polycyclic aromatic group (e.g., phenylene or naphthylene). The prefix "halo" means a group or compound including one more halogen (F, CI, Br, or I) substituents, which can be the same or different. The prefix "hetero" means a group or compound that includes at least one ring member that is a heteroatom (e.g., 1, 2, or 3 heteroatoms, wherein each heteroatom is independently N, O, S, or P.

[0098] "Substituted" means that the compound or group is substituted with at least one (e.g., 1, 2, 3, or 4) substituents instead of hydrogen, where each substituent is

independently nitro (-N0₂), cyano (-CN), hydroxy (-OH), halogen, thiol (-SH), thiocyano (- SCN), Ci-6 alkyl, C_2-6 alkenyl, C_2-6 alkynyl, Ci_6 haloalkyl, C₁-9 alkoxy, Ci-6 haloalkoxy, C_3-12 cycloalkyl, C5-18 cycloalkenyl, C₆-i₂ aryl, C_7-13 arylalkylene (e.g, benzyl), C_7-12 alkylarylene (e.g, toluyl), C_4-12 heterocycloalkyl, C_3-12 heteroaryl, Ci_6 alkyl sulfonyl (-S(=0)₂-alkyl), C_6-12 arylsulfonyl (-S(=0)₂-aryl), or tosyl (CH₃C₆H₄SO₂-), provided that the substituted atom's normal valence is not exceeded, and that the substitution does not significantly adversely affect the manufacture, stability, or desired property of the compound. When a compound is substituted, the indicated number of carbon atoms is the total number of carbon atoms in the group, including those of the substituent(s).

[0099] The invention is further illustrated by the following non-limiting examples.

EXAMPLES

[00100] A dixanthate chain transfer agent having an alkene-containing moiety was synthesized according to the chemical scheme of Figure 1. The dixanthate reagent was prepared by reacting cis-l,4-dichloro-2-butene with a slight molar excess of 4-hydroxybenzyl alcohol in the presence of 2 molar equivalents of potassium hydroxide, catalytic potassium iodide, and methanol as the solvent. Compound 1 in the chemical scheme of Figure 1 was isolated and characterized by nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry. Compound 1 was further reacted with two molar equivalents of phosphorus tribromide, followed by reaction with potassium ethyl xanthate to give the dixanthate chain transfer agent shown as compound 3 in the chemical scheme of Figure 1. Compound 3 was purified by column chromatography on silica gel, and isolated as a pale yellow solid or a white, fluffy solid, depending on the method of drying. The structure of compound 3 was verified by NMR spectroscopy and mass spectrometry.

[00101]The dixanthate chain transfer agent can be used for controlled radical polymerization of alkene-containing monomers and metathesis polymerization of olefins, specifically cyclic olefins. As shown in the chemical scheme of Figure 2, polycyclooctene samples having xanthate end-groups with differing molecular weights and dispersities (D) typical of ROMP were prepared by adjusting the molar ratio of the chain transfer agent and the cyclic olefin monomer. Samples were synthesized using [l,3-bis-(2,4,6-trimethylphenyl)- 2-imidazolidinylidene]dichloro(phenylmethylene)(tricyclohexylphosphine)-ruthenium (known as Grubbs' 2^nd generation catalyst) and cis-cyclooctene at 40°C in a dichloromethane solution. The molecular weight of polycyclooctene prepared by ROMP from the dixanthate transfer agent was found to be inversely proportional to the amount of dixanthate agent employed in the polymerization.

[00102] Samples of mid-functional poly(vinyl acetate) (PVAc) were synthesized by RAFT polymerization using azobisisobutyronitrile (AIBN) as initiator and the dixanthate chain transfer agent, as shown in the chemical scheme of Figure 3. The molar ratio of initiator to chain transfer agent was 1 :5 and the RAFT polymerization was conducted at 70°C for the desired time intervals. The resulting polymers had dispersity values of 1.20 to 1.30 , suggesting that the polymerization was well-controlled. The polymers were synthesized in a range of number average molecular weights from 5,000 to 20,000 grams/mole (g/mol).

Molecular weight characterization was performed on an Agilent 1260 series gel permeation chromatography (GPC) system in tetrahydrofuran (TFIF) relative to polystyrene standards. Number average molecular weight determined by GPC showed good correlation to molecular weight calculated from 1H NMR spectroscopy, specifically for low molecular weight polymers (e.g., less than 10,000 g/mol). Molecular weight was calculated from 1H NMR spectra by comparing integration of the resonances at 7.08 ppm, 6.83 ppm and 5.90ppm, corresponding to the chain transfer agent, and the resonances at 4.86ppm and 1.60-2.14 ppm, corresponding to the vinyl acetate repeat units. 1H NMR spectroscopy was also used to verify that the cis-2-butene functionality of the chain transfer agent was retained during the RAFT polymerization, specifically noting the resonance at 5.90 ppm.

[00103]The above-described poly(vinyl acetate) polymers were used as

macromolecular chain transfer agents in the polymerization of a cyclic olefin by ROMP, forming a triblock copolymer as shown in the chemical scheme of Figure 4. Triblock copolymers were synthesized from the macromolecular chain transfer agent using Grubbs' 2^nd generation catalyst and the cyclic olefin monomer 1,5-cyclooctadiene. ROMP of 1,5- cyclooctadiene was carried out at room temperature for the desired time intervals with dichloromethane as the solvent. The triblock copolymer structure was confirmed using 1H NMR spectroscopy, and molecular weight was determined by GPC in TFIF relative to polystyrene standards. The data demonstrate the insertion efficiency of the cyclic monomer is not dependent on the molecular weight of the poly(vinyl acetate) macromolecular chain transfer agent (e.g., greater than 80% cyclic olefin incorporation for macromolecular chain transfer agents having molecular weights of 8,000 daltons (Da) and 15,000 Da), as shown in Figure 5. As used herein, the term "insertion efficiency" refers to the mole percent of cyclic olefin monomer repeat units present in the triblock copolymer. Examples of triblock copolymers having varying molecular weight and compositions are shown in Table 1.

Molecular weights shown in Table 1 were determined by 1H NMR spectroscopy, and are reported in Da. The dispersity was determined using GPC in TFIF relative to polystyrene standards.

Table 1 : Examples of poly(vinyl acetate)-£-polyolefin-£-poly(vinyl acetate). Sample M_n poly(vinyl M_n polyolefin M_n triblock Dispersity (D) acetate) copolymer

1 3,800 1,600 5,400 1.31

2 7,600 12,500 19, 100 1.73

3 14,700 23,200 38,000 1.79

[00104] A polymer membrane comprising the triblock copolymers was prepared by dissolving the poly( vinyl acetate)-£-polybutadiene-£-poly(vinyl acetate) triblock copolymer in ethyl acetate. The polymer solution was added to a container having an aqueous solution of saturated sodium chloride (brine) and a uniform layer formed. The container was left under a stream of nitrogen and air for a desired time interval until the ethyl acetate had evaporated, leaving a uniform layer of the triblock copolymer on the surface of the brine solution. The polymer membrane was exposed to ultraviolet light (λ=302 nm) for a desired time interval to effect cross-linking.

[00105]Poly( vinyl alcohol)-£-polyolefin-£-poly(vinyl alcohol) was obtained, for example, by solid state hydrolysis of poly(vinyl acetate)-£-polybutadiene-£-poly( vinyl acetate) crosslinked polymer membranes. The transformation of the vinyl acetate groups to alcohol groups is shown in the chemical scheme of Figure 6. The free-standing polymer membrane was immersed in a saturated aqueous solution of potassium hydroxide (e.g., about 55 weight percent potassium hydroxide in water) for a desired time period at 20 to 50°C, with mild stirring so as not to disrupt the membrane structure. The polymer membrane was washed with water and dried under reduced pressure. Infrared (IR) spectroscopy was used to confirm the removal of the acetate group, yielding a polymer membrane comprising the triblock copolymer poly(vinyl alcohol)-£-polybutadiene-£-poly(vinyl alcohol). IR

spectroscopy further confirmed that while complete conversion was achieved at the exterior of the membrane, only partial conversion was achieved at the interior of the membrane. The partially-converted films showed improvements in mechanical strength compared to the films prior to hydrolysis.

[00106]Experimental details follow.

[00107]Materials. 4-hydroxybenzyl alcohol, cis-l,4-dichloro-2-butene, phosphorus tribromide, potassium ethyl xanthate, diisopropylethylamine, cesium carbonate, potassium carbonate and silica gel were purchased from VWR and used as received. Vinyl acetate monomer was obtained from VWR, and prior to polymerization was passed through a column of aluminum oxide to remove inhibitor. Hexanes, ethyl acetate, methanol, magnesium sulfate anhydrous, potassium hydroxide were purchased from Fisher Chemical and used as received. 2,2'-Azobisisobutyronitrile (AIBN) was obtained from Sigma-Aldrich and recrystallized from methanol. The second generation (G2) Grubbs catalyst (IMesH₂)(Cy₃P)RuCl₂(CHPh) was purchased from Sigma-Aldrich and used as received. 1,5-Cyclooctadiene was purchased from Sigma-Aldrich and used as received, or purified by fractional distillation.

[00108]Characterization. 1H (300 MHz) and ¹ C (75 MHz) NMR spectra were recorded on a Bruker Spectrospin 300 NMR spectrometer with the samples dissolved in chloroform-di (CDC1₃), dimethylsulfoxide-d₆ (DMSO-d₆), dichloromethane-d₂ (CD₂C1₂), or 1,1,2,2-tetrachloroethane (TCE-d²) (C₂D₂C1₄). Molecular weight and dispersity were measured by gel permeation chromatography (GPC) in THF at 40°C with a flow rate of 1 milliliter/minute on an Agilent 1260 series system, equipped with a refractive index (RI) and ultraviolet (UV) detectors, and two 5 micrometer analytical Mixed-C columns and one 5 micrometers analytical Mixed-D column from Agilent (300 x 7.5 millimeters). Fourier transform infrared (FTIR) spectroscopy was performed on a Perkin-Elmer Spectrum 100 with a universal ATR sampling accessory at room temperature.

[00109]Synthesis of (Z)-l,4-bis(4-hydroxymethylphenoxy)but-2-ene (1). (Z)-l,4- bis(4-hydroxymethylphenoxy)but-2-ene (shown as compound 1) was prepared as

summarized in the chemical scheme of Figure 1. Potassium hydroxide (9.3 grams, 160 millimoles) and cesium carbonate (2.0 grams, 6 millimoles) were dissolved in methanol (200 milliliters). Once the potassium hydroxide was fully dissolved, 4-hydroxybenzyl alcohol (19.8 grams, 160 millimoles) was added. The solution was heated to 40°C for 2 hours, at which point the solution turned red. Cis-l,4-dichloro-2-butene (10 grams, 80 millimoles) was added to the stirring solution dropwise. The solution was maintained at 40°C for 4 days. Methanol was removed by evaporation, and the remaining solid was washed with 1 Molar KOH (aqueous) and then rinsed with deionized water multiple times. The residue was dried under vacuum for 2 days to yield a white powder (18.84 grams, 79% yield). 1H NMR

(DMSO-de, ppm): δ 7.19 (d, J = 8.5 Hz, 4H, Ph), 6.88 (d, J = 8.5 Hz, 4H, Ph), 5.99 - 5.65 (m, 2H, CH=CH), 5.05 (s, 2H, OH), 4.67 (d, J = 3.7 Hz, 4H, benzyl), 4.38 (s, 4H, CH=CH-CH₂).

[00110]Synthesis of (Z)-l,4-bis(4-(ethyl xanthate methyl )phenoxy)but-2-ene (3). (Z)-l,4-bis(4-(ethyl xanthate methyl )phenoxy)but-2-ene (shown as compound 3) was prepared as summarized in the chemical scheme of Figure 1. (Z)-1,4-Bis(4- hydroxymethylphenoxy)but-2-ene (Compound 1) (18.45 grams, 61.5 millimoles) was added to a solution of N,N-diisopropylethylamine (17.3 grams, 135 millimoles) in anhydrous ethyl acetate (300 milliliters). The mixture was stirred for 1 hour to obtain a suspension. The flask was protected from light and cooled to 0°C. Phosphorus tribromide (18.65 grams, 68.8 millimoles) was added to the reaction mixture dropwise. The solution was kept in the dark and warmed to room temperature over the course of 1 hour. The product was washed with a potassium carbonate solution, and with brine solution several times. The organic portion was dried over MgS0₄ and filtered to give a solution of compound 2. Potassium ethyl xanthate (11.2 grams, 70 millimoles) was added directly to the filtered solution of compound 2 without any further purification and stirred at room temperature for 18 hours. The solution was washed with brine several times. The organic portion was dried over MgS0₄ and the volatiles were removed in vacuo. The crude product was further purified by silica gel column chromatography, eluting with hexane/ethyl acetate mixtures ranging from 10: 1 to 5: 1. The compound 3 product was isolated as a light yellow solid after drying under vacuum, or a white fluffy solid after drying under a stream of nitrogen (11.2 grams, 64.4% yield). 1H NMR (CD₂Cl₂-d₂, ppm): δ 7.27 (d, J= 8.6 Hz, 4H,Ph), 6.85 (d, J= 8.6 Hz, 4H,Ph), 5.90 (t, J = 3.5 Hz, 2H, CH=CH), 4.87 - 4.34 (m, 8H, =CH-CH₂ & CH₂CH₃ ), 4.32 (s, 4H, benzyl) 1.41 (t, J= 7.1Hz, 6H,-<¾). ¹ C NMR (CDC1 , ppm): 5 =214.18, 157.86, 130.38, 128.56, 127.96, 114.79, 70.05, 64.24, 40.00, 13.88. MS (ESI): m/z = 531 (M+Na⁺).

[0011 l]Synthesis of dixanthate functionalized polycyclooctene. A dixanthate- terminated poly(cyclooctene) was prepared as summarized in Figure 2. (Z)-l,4-bis(4-(ethyl xanthate methyl )phenoxy)but-2-ene (Compound 3) (0.10 grams, 0.20 millimoles) and cyclooctene (0.20 grams, 1.8 millimoles) were dissolved in tetrahydrofuran (0.6 grams). The solution was added to a solution of (IMesH₂)(Cy P)RuCl₂(CHPh) (Grubbs' 2^nd generation catalyst) (4.6 milligrams, 5.4 micromoles) in tetrahydrofuran (0.2 grams). The solution was stirred at 35°C for 1 hour. Following polymerization, volatiles were removed under vacuum. The end-functionalized polymer was characterized by NMR spectroscopy and gel permeation chromatography. 1H NMR (300 MHz, CD₂C1₂) 5 7.31 - 7.20 (d, Ph), 6.92 - 6.79 (d, Ph), 5.88 - 5.66 (m, CH=CH), 5.46 - 5.32 (m, CH=CH), 4.64 (q, 0-CH₂-CH₃), 4.44 (d,CH=CH- CH2-0), 4.31 (s, benzyl), 2.17 - 1.85 (br, CH=CH₂-CH₂-CH₂), 1.48 - 1.19 (br, -CH₂-). GPC (40°C, THF) (M_n=2,000 Da, D =1.80).

[00112]Table 2 is a summary of conditions and results for ROMP polymerizations of cis-cyclooctene. Number average molecular weight (Mn) was determined using 1H NMR spectroscopy, and is reported as Da. GPC in THF against polystyrene standards was used to determine Mn and polydispersity (D). Table 2: Examples of dixanthate functionalized polycyclooctene.

[00113] Synthesis of cis-2-butene mid-functional poly(vinyl acetate). A mid- functional poly(vinyl acetate) was prepared as summarized in Figure 3. Vinyl acetate (51.66 grams, 0.6 moles) was added to a reaction tube containing a mixture of dixanthate chain transfer agent (Compound 3; 1.016 grams, 2 millimoles) and AIBN (65.6 milligrams, 0.4 millimoles). The mixture was degassed by bubbling with nitrogen for 1 hour, followed by stirring at 70°C for 8 to 24 hours (depending on the target molecular weight). The poly( vinyl acetate) product was obtained by dissolution of the bulk reaction mixture in ethyl acetate, followed by precipitation in hexane. The poly(vinyl acetate) was precipitated several times to completely remove unreacted monomer. 1H NMR (300 MHz, CDCl₃-di) δ 7.06 (d, J = 7.6 Hz, Ph), 6.81 (d, J = 6.9 Hz, Ph), 5.90 (s, CH=CH), 4.85 (s, -CH₂-CH-OCO), 4.62 (s, benzyl), 2.14 - 1.92 (br, OCO-C¾), 1.78 (br, -C%-CH-OCO).

[00114] Table 3 is a summary of conditions and results for RAFT polymerizations of vinyl acetate. Number average molecular weight (Mn) was determined using 1H NMR spectroscopy, and is reported as Da. GPC in THF against polystyrene standards was used to determine Mn and polydispersity (D). Percent conversion of monomer to polymer was determined using 1H NMR spectroscopy.

Table 3 : Examples of mid-functional poly(vinyl acetate).

[00115] Synthesis of poly(vinyl acetate)-Z>-polybutadiene-Z>-poly(vinyl acetate). A poly(vinyl acetate)-£-polybutadiene-£-poly( vinyl acetate) triblock copolymer was prepared as summarized in Figure 4. Mid-functional poly( vinyl acetate) (4.2 grams, 0.6 millimoles, M„=7,000 grams/mole) and (IMesH₂)(Cy₃P)RuCl₂(CHPh) (Grubbs' 2^nd generation catalyst) (24.7 milligrams, 0.03 millimoles) were added to a reaction tube, which was evacuated and refilled with nitrogen. Dichloromethane (anhydrous, 150 milliliters) was cannulated into the reaction tube. 1,5-Cyclooctadiene (10.8 grams, 0.1 moles) was degassed by three cycles of freeze-pump-thaw followed by cannulation to the reaction tube. The mixture stirred at 45°C for 70 hours, until the solution turned yellow. Following polymerization, volatiles were removed by rotary evaporation. The triblock copolymer was dissolved in ethyl acetate at 57°C, giving a green solution, followed by cooling to 0°C to cause formation of a suspension. Centrifugation was used to isolate the green solution (forming a bottom layer). The white gel (forming an upper layer) (1.05 grams) was discarded. The purified polymer was obtained as green waxy solid 13.9 grams, 90.3% yield). 1H NMR (300 MHz, TCE-d₂): δ 7.04 (d, J = 7.6 Hz, Ph), 6.78 (d, J = 6.9 Hz, Ph), 5.37 (s, CH=CH), 4.88 (s, -CH₂-CH-OCO), 2.14 - 1.92 (br, OCO-CH5 & CH=CH-C¾), 1 72 (br, -C¾-CH-OCO).

[00116] Preparation of polymer membranes. Polymer membranes were prepared from poly( vinyl acetate)-£-polybutadiene-£-poly( vinyl acetate). A polymer solution of poly(vinyl acetate)-£-polybutadiene-£-poly( vinyl acetate) in ethyl acetate was prepared at a concentration of 5 weight percent. A container was filled with aqueous saturated brine solution, and the polymer solution (3-10 milliliters) was transferred to the top of the brine solution, forming a uniform layer. The container was left under nitrogen/air atmosphere for one day, at which point the ethyl acetate had evaporated, leaving a uniform membrane on the surface. The resulting polymer membrane was exposed to 302 nm UV light overnight to effect cross-linking.

[00117] Polymer membranes comprising poly(vinyl alcohol)-£-polybutadiene-£- poly(vinyl alcohol) were prepared by solid state hydrolysis as summarized in the chemical scheme of Figure 6.

[00118] Solid state hydrolysis of polymer membranes. The poly( vinyl acetate)-£- polybutadiene-£-poly(vinyl acetate) polymer membrane was immersed in a saturated aqueous solution of potassium hydroxide (KOH) for seven days at room temperature or 50°C, with mild stirring so as not to disrupt the structure of the membrane. The resulting film was washed with water and dried under reduced pressure. Infrared (IR) spectroscopy was used to confirm the hydrolysis, forming a free-standing polymer membrane comprising poly( vinyl alcohol)-£-polybutadiene-£-poly(vinyl alcohol).

Claims

CLAIMS:

1. A triblock copolymer having the structure

wherein

Z is independently at each occurrence a polymer block comprising a poly( vinyl acetate), a poly(vinyl alcohol), or a poly(vinyl acetate-co-vinyl alcohol);

A is a polyolefin block;

L¹ is independently at each occurrence a group that is (-CH₂-)_X, wherein x is an integer from 1 to 10;

L² is independently at each occurrence a C₁-C₁₂ alkylene group or C5-C₁₂ arylene group;

R¹ and R² are independently at each occurrence hydrogen, a C₁-C₁₂ alkyl group, a C₆- C₂₀ aryl group, a C₁-C₂₀ alkoxy carbonyl group, or a cyano group; and

y is independently at each occurrence 0 to 4.

2. The triblock copolymer of claim 1, wherein the polyolefin is a polycyclooctene or a polybutadiene.

3. The triblock co olymer of claim 1, having the structure

wherein

n is independently at each occurrence 0, 1, 2, 3, or 4; and

R³ is independently at each occurrence occurrence halogen, cyano, thiocyanato, nitro, C2-C12 alkylamido, C1-C12 alkyl, C1-C12 alkoxyl, C1-C12 alkylthio, C3-C12 cycloalkyl, C2-C12 acyl, C₆-Ci2 aryl, C3-C20 heteroaryl, or C1-C12 carbamoyl.

4. The triblock copolymer of claim 3, wherein

the polyolefin is a polycyclooctene or a polybutadiene;

each occurrence of L¹ is methylene (-CH₂-); and

each occurrence of n is 0.

5. A polymer membrane comprising the triblock copolymer of claim 1.

6. A chain transfer agent having the structure

wherein

L² is independently at each occurrence a C1-C12 alkyl group or C₆-Ci2 aryl group; and R¹ and R² are independently at each occurrence hydrogen, a C1-C12 alkyl group, a C₆- C20 aryl group, a C1-C20 alkoxy carbonyl group, or a cyano group;

y is independently at each occurrence 0 to 4;

p is independently at each occurrence 0 or 1;

X is independently at each occurrence - R⁵-, -0-, or -S-, wherein R⁵ is hydrogen, Ci- C12 alkyl, C3-C12 cycloalkyl, C₆-Ci2 aryl, C2-20 alkenyl, C7-20 aralkyl, optionally substituted with one or more in-chain or pendent heteroatoms selected from the group consisting of oxygen, nitrogen, and sulfur; and

R⁴ is independently at each occurrence C1-C20 alkyl, C3-C12 cycloalkyl, or C6-C20 aryl, C2-20 alkenyl, C7-20 aralkyl, C2-7 acyl, optionally substituted with one or more in-chain or pendent heteroatoms selected from the group consisting of oxygen, nitrogen, and sulfur; provided that when X is -NR⁵-, R⁴ can optionally combine to form a ring with R⁵.

7. The chain transfer agent of claim 6, having the structure

wherein

n is independently at each occurrence 0, 1, 2, 3, or 4;

p is independently at each occurrence 1; and

R² is independently at each occurrence occurrence halogen, cyano, thiocyanato, nitro, C2-C12 alkylamido, C1-C12 alkyl, C1-C12 alkoxyl, C1-C12 alkylthio, C3-C12 cycloalkyl, C2-C12 acyl, C₆-Ci2 aryl, C3-C20 heteroaryl, or C1-C12 carbamoyl.

8. The chain transfer agent of claim 7, wherein

each occurrence of L¹ is methylene (-CH₂-);

each occurrence of n is 0;

each occurrence of each occurrence of X is -0-; and

each occurrence of R⁴ is ethyl.

9. A method of preparing the triblock copolymer of claim 1, the method comprising, polymerizing vinyl acetate in the presence of a chain transfer agent having the structu

L² is independently at each occurrence a Ci-Ci₂ alkylene group or C₆-Ci₂ arylene group;

R¹ and R² are independently at each occurrence hydrogen, a Ci-Ci₂ alkylene group, a C₆-C₂o arylene group, a Ci-C₂₀ alkyloxy carbonyl group, or a cyano group;

y is independently at each occurrence 0 to 4;

p is independently at each occurrence 0 or 1 ;

X is independently at each occurrence - R⁵-, -0-, or -S-, wherein R⁵ is hydrogen, Ci-C₁₂ alkyl, C₃-Ci₂ cycloalkyl, C₆-Ci₂ aryl, C_2-20 alkenyl, C_7-2o aralkyl, optionally substituted with one or more in-chain or pendent heteroatoms selected from the group consisting of oxygen, nitrogen, and sulfur; and

R⁴ is independently at each occurrence Ci-C₂₀ alkyl, C -Ci₂ cycloalkyl, or C₆-C₂o aryl, C_2-2o alkenyl, C_7-2o aralkyl, C_2-7 acyl, optionally substituted with one or more in-chain or pendent heteroatoms selected from the group consisting of oxygen, nitrogen, and sulfur;

provided that when X is -NR⁵-, R⁴ can optionally combine to form a ring with R⁵;

to provide a macro-chain transfer agent comprising a poly(vinyl acetate); and polymerizing a cyclic olefin in the presence of the macro-chain transfer agent to provide the triblock copolymer.

10. The method of claim 9, further comprising hydro lyzing the triblock copolymer to provide a triblock copolymer comprising poly(vinyl alcohol).

11. A mid-functional polymer having the structure

wherein

L² is independently at each occurrence a C1-C12 alkylene group or C₆-Ci2 arylene group; and

R¹ and R² are independently at each occurrence hydrogen, a C1-C12 alkylene group, a C6-C20 arylene group, a C1-C20 alkyloxy carbonyl group, or a cyano group;

y is independently at each occurrence 0 to 4;

p is independently at each occurrence 0 or 1;

12. The mid-functional polymer of claim 11, wherein

each occurrence of L¹ is methylene (-CH₂-);

each occurrence of L² is phenylene;

each occurrence of R¹ and R² are hydrogen;

each occurrence of y is 1;

each occurrence of p is 1; each occurrence of X is -0-; and

each occurrence of R⁴ is ethyl.

13. The mid-functional polymer of claim 11, having the structure

wherein

n is independently at each occurrence 0, 1, 2, 3, or 4;

each occurrence of p is 1; and

14. A polyolefin having the structure

wherein

A is a polyolefin block;

y is independently at each occurrence 0 to 4;

p is independently at each occurrence 0 or 1;

R⁴ is independently at each occurrence C1-C20 alkyl, C3-C12 cycloalkyl, or C6-C20 aryl, C2-20 alkenyl, C₇-20 aralkyl, C2-7 acyl, optionally substituted with one or more in-chain or pendent heteroatoms selected from the group consisting of oxygen, nitrogen, and sulfur; provided that when X is - R⁵-, R⁴ can optionally combine to form a ring with R⁵.

15. The polyolefin of claim 14, wherein the polyolefin is a polybutadiene or a

polycyclooctene.

16. The polyolefin of claim 14, wherein

each occurrence of L¹ is methylene (-CH₂-);

each occurrence of L² is phenylene;

each occurrence of R¹ and R² are hydrogen;

each occurrence of y is 1;

each occurrence of p is 1;

each occurrence of X is -0-; and

each occurrence of R⁴ is ethyl.

17. The olyolefin of claim 14, having the structure

wherein

n is independently at each occurrence 0, 1, 2, 3, or 4;

p is independently at each occurrence 1; and