CN101891843B - Preparation method of hyperbranched polyvinyl acetate - Google Patents

Abstract

The invention belongs to the field of high molecular materials, in particular relates to a method for preparing a hyperbranched polyvinyl acetate polymer with a controllable structure. Vinyl acetate is used as a monomer and azodiisobutyronitrile is used as an initiating agent to form a reversible addition-fragmentation chain transfer (RAFT) polymerization system with a RAFT reagent, and 1,4-dioxane is used as a solvent to prepare the hyperbranched polyvinyl acetate in an inert atmosphere, wherein the RAFT reagent is (2-ethoxycarbonothioylthio) vinyl acetate (ECTVA). In the invention, the ECTVA is used for regulating and controlling the polymerization of VAc monomers, and the synthesis of the hyperbranched PVAc polymer with the controllable structure is successfully realized for the first time by combining the SCVP technology and the RAFT technology; and compared with the straight chain polymers, the prepared hyperbranched PVAc polymer has better capacity of dispersing gold nanoparticles.

Description

A kind of preparation method of hyperbranched polyvinyl acetate

Technical field

The invention belongs to polymeric material field, be specifically related to a kind of method for preparing the hyperbranched polyvinyl acetate polymkeric substance of controllable structure.

Background technology

Branching macromole (Dendritic macromolecules) is one of focus of polymeric material field research in recent years.According to the macromolecular constitutional features of branching, can it be divided into dendritic macromole (Dendrimer) and hyperbranched polymer (Hyperbranched po1ymers).The branching macromole is owing to have highly branched structure; Thereby show the performance different with line polymer, for example the viscosity of easy entanglement, solution and body is not low, molecular structure is spherical in shape and molecule chain end has a large amount of functional group etc. for its molecular chain.Wherein dendritic macromole is because its structural perfection (symmetry of zero defect and height etc.); Receive the concern of educational circles at first; But no matter dendritic macromole is synthetic or synthetic through convergence method through the method for dispersing; All need pass through polystep reaction and purifying, loaded down with trivial details building-up process and high cost have hindered its industrialized application greatly.On the other hand; In the application in a lot of fields; Perfectly dendritic structure is not necessary condition, and what for example when improving viscosity, need mainly is the globosity of its highly branched formation, and what need as the linking agent of coating then mainly is its LV and a large amount of terminal reactive groups.Therefore; The hyperbranched polymer conduct begins to get into people's the visual field with a family macromolecule of dendritic macromole similar; And since its structure similar and characteristic with dendritic macromole with and synthesize and outclass the advantage of dendritic macromole, so be considered to have the prospect of heavy industrialization from the beginning.Because for the pursuit of perfect structure, reaction need not passed through the synthetic and purifying of multistep to hyperbranched polymer, can obtain required polymkeric substance by monomer is synthetic through single stage method, thereby greatly reduce the synthetic cost.In addition; The existence of a large amount of functional groups makes its polymkeric substance that can obtain various different qualities and special purpose through modification, has shown from coating, tackiness agent, auxiliary rheological agents to huge using values of numerous areas such as supramolecular chemistry, nanosecond science and technology, biomaterial, photovaltaic material, medicine deliveries.

The preparation method of hyperbranched polymer roughly is divided into polycondensation, ring-opening polymerization and living polymerization etc.And wherein (self-condensing vinyl polymerization is SCVP) (referring to Fre ' chet, J.M.J. from the condensation vinyl polymerization; Henmi, M.; Gitsov, I.; Aoshima, S.; Leduc, M.R.; Grubbs, R.B.Science 1995,269, and 1080-1083) method is because its implementation condition and polymer process easily flexibly, since the nineteen ninety-five reported first, become one of important method that hyperbranched polymer prepares from people such as Fr é chet.With SCVP polymerization technique and living polymerization, particularly living radical polymerization technique combines, for a flexible and changeable and simple and easy to do approach has been opened up in the synthetic and design of hyperbranched polymer.Common living radical polymerization technique mainly contains living free radical polymerization polymerization (NMP), ATRP (ATRP) and RAFT polymerization (RAFT).This technology has the consistency of functional groups high; Polymerization technique is easy; Characteristics such as implementation method is versatile and flexible are therefore since last century, the nineties came to light, through the develop rapidly in twenty or thirty year; Become the strong instrument that utilizes Polymer Synthesizing designing and preparing functional materials, be widely used in the polymkeric substance of each class formation such as block, pectination, star synthetic in.Utilize living radical polymerization technique and SCVP to combine, the preparation that has successfully realized multiple monomeric hyperbranched polymers such as styrene-based and methyl acrylic ester is (referring to (1) Matyjaszewski, K.; Xia, J.Chem.Rev.2001,101,2921-2990.; (2) Hawker, C.J.; Fre ' chet, J.M.J.; Grubbs, R.B.; Dao, J.J. Am.Chem.Soc.1995,117,10763-10764.; (3) Gaynor, S.G.; Edelman, S.Z.; Matyjaszewski, K.Macromolecules 1996,29, and 1079.; (4) Matyjaszewski, K.; Gaynor, S.G.; Kulfan, A.; Podwika, M.Macromolecules 1997,30,5192-5194.).Through the adjusting of polymerization technique, regulation and control that can smooth implementation polymer chain segment structure, polymerization process shows active controlled characteristic.

PVA (PVAc) is because its outstanding physicals and biocompatibility are one of important polymkeric substance.Be widely used in the fields such as building, weaving, packing, printing, wood working, coating and tackiness agent.Simultaneously, through further reaction,, can obtain another important polymkeric substance Z 150PH (PVA) one by one with wherein ethanoyl hydrolysis.Therefore, vinyl acetate (VAc) often is used as functional element and introduces in the polymer segment, realizes having the preparation of specific functionality polymer materialss such as good biocompatibility.Yet because VAc belongs to non-conjugative monomer, two keys directly do not link to each other with carbonyl in its structure, and the success ratio that employing NMP and ATRP legal system are equipped with controllable structure PVAc is not high, and adopts the RAFT rule relatively easily to realize.Through selecting the sulphur ortho ester as regulation and control reagent, can carry out the monomeric active free radical polymerization process of VAc smoothly, this technology is become macromole designing technique (MADIX) under the xanthate regulation and control again (referring to Richard, R.E.; Schwarz, M.; Ranade, S.; Chan, A.K.; Matyjaszewski, K.; Sumerlin, B.Biomacromolecules 2005,6,3410-3418.).

At present, there are many documents to carry out the monomeric RAFT process study of VAc, prepared corresponding polymer (referring to (1) H.S.Martina, C.Lyndal; G.E.Roberts, Macromol.Chem.Phys.2003,204; 1160-1168. (2) F.Arnaud, B.K.Christopher, P.D.Thomas; Macromol.Chem.Phys.2004,205,925.).Yet; Research for the monomeric hyperbranched polymer of VAc is but very rare; For example people such as Bernard has synthesized two kinds of xanthate reagent, and (referring to Corinne E.Lipscomb and Mahesh K.Mahanthappa, Macromolecules 2009 to synthesize pectination PVAe; 42,4571-4579); Bernard etc. synthesized four kinds of xanthate reagent synthesize star PVAc (referring to Julien B., Arnaud F., Thomas P. D., Christopher B., Martina H.S., Polymer 2006,47,1073-1080); Sherrington seminar has reported that the PVAc that utilizes three TTT and VAe copolymerization branched structure is (referring to Julien B., Arnaud F., Ling Z.; Anastasia N., Thomas P. D., Christopher B.; Martina H.S.; Macromolecules 2005,38,5475-5484).Yet the hyperbranched polymer molecule amount that this method makes distributes wide, and MWD can not be well controlled.

Summary of the invention

The object of the invention provides a kind of preparation method of hyperbranched polyvinyl acetate.

For achieving the above object, the technical scheme that the present invention adopts is: a kind of preparation method of hyperbranched polyvinyl acetate is a monomer with vinyl acetate (VAc); Diisopropyl azodicarboxylate (AIBN) is an initiator; Constitute RAFT polymerization (RAFT) system with RAFT reagent, with 1, the 4-dioxane is a solvent; In inert atmosphere, the preparation hyperbranched polyvinyl acetate; Wherein said RAFT reagent be (2-oxyethyl group dithio perester radical) vinyl acetate (2-(ethoxycarbonothioylthio) vinyl acetate, ECTVA).

In the technique scheme, monomer: RAFT reagent: initiator mol ratio be 10～200: 1: 0.5～1; Said polymerization temperature is 40～120 ℃, and said polymerization time is 15～360 minutes; Preferably, said polymerization temperature is 50～70 ℃.

In the technique scheme, the chemical structural formula of said RAFT reagent is as follows:

Further in the technical scheme, above-mentioned polymerisate dissolves with THF, pours in the sherwood oil then and precipitates; Treat deposition fully, topple over and sherwood oil that the vacuum-drying polymkeric substance promptly obtains hyperbranched polyvinyl acetate to constant mass.

The present invention requires to protect above-mentioned RAFT reagent simultaneously, and the preparation method of said RAFT reagent may further comprise the steps: ethyl sulphur ortho acid potassium is dissolved in the anhydrous propanone, and stirring at room dissolving back drips vinyl chloroacetate; The mixture stirring at room is 12h at least, removes by filter insoluble inorganic salt, and filtrating is through deionized water wash; And behind dichloromethane extraction, use anhydrous magnesium sulfate drying; The pressure reducing and steaming solvent obtains thick product, the thick product that obtains is made use column chromatography purification.

Because the technique scheme utilization, the present invention compared with prior art has advantage:

1, the present invention's sulphur ortho ester of having selected to have the oxyethyl group structure is as structural unit; Through in structure, introducing two keys; (2-(ethoxycarbonothioylthio) vinyl acetate (ECTVA) is a RAFT reagent with ECTVA, utilizes the monomeric polymerization of ECTVA regulation and control VAc to have designed and synthesized corresponding sulphur ortho ester (2-oxyethyl group dithio perester radical) vinyl acetate; Combine with the RAFT technology through SCVP, successfully realized hyperbranched PVAc polymkeric substance synthetic of controllable structure first.

2, polymerization result of the present invention shows, its polymerization kinetics and monomer concentration oblatio one-level linear relationship, polymericular weight be linear increasing with the increase of monomer conversion; The resulting polymers molecular weight distributing index is between 1.2～2.5; Resulting polymers can carry out chain extending reaction through further interpolation VAc monomer; These results show that jointly polymerization process is active controlled process.

3, the present invention can realize the regulation and control of the polymkeric substance degree of branching, and the polymkeric substance degree of branching of nuclear magnetic resonance method determination conforms to Theoretical Calculation gained degree of branching numerical value through regulating ECTVA and VAc ratio.

4, the hyperbranched PVAc polymkeric substance of gained of the present invention has the ability than the better dispersing nanometer gold of straight-chain polymer.

Description of drawings

Fig. 1 is the synthetic route chart of sulphur ortho ester ECTVA among the embodiment and the preparation wiring diagram of hyperbranched PVAc polymkeric substance;

Fig. 2 is monomer concentration semilog and a polymerization time graph of a relation in the VAc monomer polymerization process among the embodiment one;

Fig. 3 is the graph of a relation of polymericular weight and MWD and transformation efficiency in the VAc monomer polymerization process among the embodiment one;

Fig. 4 is that ECTVA regulates and control the GPC elution curve figure of VAc monomer polymerization resulting polymers down among the embodiment three;

Fig. 5 is PVAc polymkeric substance chain extending reaction front and back GPC elution curve figure among the embodiment four;

Fig. 6 is the hydrogen nuclear magnetic resonance spectrogram of hyperbranched PVAc polymkeric substance among the embodiment two;

Fig. 7 is the stable TEM picture of nanometer gold down of polymer P VAc among the embodiment five, wherein, and the nanometer gold (M under (a) hyperbranched polymer is stablized _n=10800, M _w/ M _n=2.37)/HAuCl ₄=1: 1; (b) nanometer gold (M under linear polymer is stablized _n=5600, M _w/ M _n=1.41)/HAuCl ₄=1: 1.

Embodiment

Below in conjunction with accompanying drawing and embodiment the present invention is further described:

Embodiment one: the RAFT polymerization of vinyl acetate as shown in Figure 1

(1) raw material and reagent

Potassium ethyl xanthonate (Alfa Aesar, 98%); Vinyl chloroacetate (Shanghai chemical reagents corporation, 98%); Methyl-sulphoxide (analytical pure, Shanghai chemical reagents corporation); Vinyl acetate (VAc, analytical pure, Shanghai chemical reagents corporation) is crossed the neutral alumina pillar with preceding, and is kept in the refrigerator; Diisopropyl azodicarboxylate (AIBN, analytical pure, Shanghai chemical reagents corporation), with preceding through twice recrystallization; 1; 4-dioxane (analytical pure; Shanghai chemical reagents corporation),

molecular sieve drying.Chemical reagents corporation buys other reagent from Shanghai, and directly uses.

Testing tool:

INOVA 400 MHz NMRs (DMSO-d6 is a solvent, and TMS is interior mark) are measured the structure of compound; Waters 1515 type gel permeation chromatographs (GPC) are equipped with HR 1; HR 2 and HR4 (7.8 * 300mm2,5 μ tm microballoons are filled) separator column, Waters717 automatic sampling instrument and 2540 differential detectors; PS with narrow distribution is a standard specimen, measures polymericular weight and MWD; EA1110CHNO-S type elemental analyser; Waters 515 type high performance liquid chromatographs (HPLC) are equipped with UV-detector and C18 separator column; The JEM-1010 of JEOL company type transmission electron microscope (TEM); Sigma ultra-high speed desk centrifuge.

(2) RAFT reagent is synthetic

(2-(ethoxycarbonothioylthio) vinyl acetate (ECTVA) is synthetic according to following steps: add ethyl sulphur ortho acid potassium (8.0g 0.05mol) and dry acetone (50mL) in the there-necked flask, stirring at room dissolving back drips vinyl chloroacetate (6.0g 0.05mol) to RAFT reagent (2-oxyethyl group dithio perester radical) vinyl acetate.Mixture stirring at room 18h removes by filter insoluble inorganic salt.Filtrating is through deionized water wash, and the use anhydrous magnesium sulfate drying spends the night behind dichloromethane extraction.The pressure reducing and steaming solvent obtains thick product.It is that 20: 1 sherwood oil and ETHYLE ACETATE is purified through column chromatography for separation as developping agent that the thick product that obtains is used volume ratio, obtains the aqueous product 6.76g of pistac (productive rate 65%) at last, and its purity detects through HPLC and is higher than 99%. ¹H?NMR(δ(ppm)，DMSO-d ₆)：1.33(OCH ₂CH ₃，3H，t)，4.20(COCH ₂-S，2H，s)，4.59(OCH ₂CH ₃，2H，q)，4.74(CH ₂＝CHO，1H，d)，4.97(CH ₂＝CHO，1H，d)7.28(CH ₂＝CHO，1H，q)。

Said preparation process is as follows:

(3) the RAFT polymerization of vinyl acetate

With vinyl acetate (VAc) is monomer, and synthetic ECTVA is a RAFT reagent, and Diisopropyl azodicarboxylate (AIBN) is an initiator; Carry out polymerization according to following ratio, VAc: ECTVA: AIBN=10～200: 1: 0.5～1, VAc concentration are 5.42mol/L; Add monomer successively, initiator, RAFT reagent solvent (1; The 4-dioxane) in the 5ml ampoule, logical argon gas 10min places the oil bath under the steady temperature (60 ℃) to react preset time (15～360min) ampoule behind the tube sealing.After reaction finishes, take out tube sealing, with the cold water cooling, open tube sealing immediately,, pour in the sherwood oil and precipitate with the THF dissolving.Treat deposition fully, topple over and sherwood oil that polymkeric substance dries by the fire and causes constant mass, promptly obtains hyperbranched polyvinyl acetate in vacuum drying oven.

Its polymerization kinetics result is as shown in Figure 2 under different ECTVA and VAc ratio condition, and resulting polymers molecular weight and MWD are as shown in Figure 3.

By result among Fig. 2 visible (γ is the mol ratio of ECTVA and VAc), the monomer concentration semilog is linear with the prolongation of polymerization time to be increased, and shows in the polymerization process that the growth number of free radical keeps constantly basically, and polymerization has the living control polymerization characteristic.Simultaneously, after ECTVA and VAc ratio increase, since the reduction of initiator A IBN concentration in the system, the also corresponding decline of its rate of polymerization.The result shows (mol ratio that γ is ECTVA and VAc) among Fig. 3, and the resulting polymers molecular weight is linear increasing along with the increase of monomer conversion.Through regulating the ratio of ECTVA and VAc, can control the molecular weight of resulting polymers.The MWD of polymerization resulting polymers is in 1.2～2.5 scopes, and this value is apparently higher than the molecular weight distribution value of the prepared polymkeric substance of common active controllable free-radical polymerisation.This mainly is because in the SCVP process; Because have two keys in the ECTVA structure, it is in as VAc polymerization adjusting and controlling reagent, two keys have wherein also been participated in polymerization process; Cause complex polymerization systemsization, the also corresponding increase of chain transfer that possibly exist and chain termination reaction.Thereby the MWD of final polymkeric substance broadens.

Embodiment two: the preparation resulting polymers degree of branching under different VAc and the ECTVA ratio condition among the detection embodiment one

The degree of branching is the important parameter of hyperbranched polymer.In this research, utilize proton nmr spectra that the degree of branching of resulting polymers is detected.The typical proton nmr spectra of polymkeric substance is as shown in Figure 6.Wherein be arranged in two keys that chemical shift about 7.2ppm belongs to polymkeric substance.The chemical shift integrated value that utilization is positioned at 4.70-4.97ppm place and 3.95-4.02 can calculate the degree of branching of polymkeric substance.Its concrete calculation formula is following:

${\mathrm{DB}}_{\mathrm{NMR}}=2\left(\frac{b}{\mathrm{\γ}+1}\right)[1-\frac{b}{\mathrm{\γ}+1}]$

b＝I _4.70-4.97/(I _3.95-4.02+I _4.70-4.97)

Utilize this formula, the degree of branching numerical value that calculates resulting polymers is as shown in table 1, and formula calculated below wherein the theoretical degree of branching of polymkeric substance was utilized:

${\mathrm{DB}}_{\mathrm{theo}}=\frac{2(1-e^{-(\mathrm{\γ}+1)})(\mathrm{\γ}+e^{-(\mathrm{\γ}+1)})}{{(\mathrm{\γ}+1)}^2}$

The preparation resulting polymers degree of branching under different VAc of table 1. and the ECTVA ratio condition

entry	γ a	T(h)	Con.(％) b	M n(g/moL) c	M w/M n c	DB NMR d	DB theo e
								1	10	6	96.3	7100	2.39	0.143	0.165
2	20	6	90.0	8000	2.44	0.085	0.091
								3	50	6	85.0	8900	2.64	0.036	0.038
4	100	6	86.4	8100	2.92	0.018	0.020
								5	200	6	60.2	9100	2.35	0.010	0.010

^aThe ratio of monomer VAc and ECTVA, γ=[VAc] ₀/ [ECTVA] ₀, ^bThe transformation efficiency of polyreaction; ^cPolymkeric substance GPC determining molecular weight; ^dThe nuclear magnetic resonance measuring polymkeric substance degree of branching; ^fThe calculated value of the polymkeric substance degree of branching;

Data presentation in the table, resulting polymers matches better through the degree of branching and the theoretical value of nuclear magnetic resonance measuring.After particularly increasing VAc and ECTVA ratio, its degree of agreement is higher.This result shows, utilizes SCVP and RAFT synizesis bonded method, can be very easily through regulating the degree of branching that regulation and control reagent and monomeric ratio are regulated resulting polymers.

Embodiment three:

According to the method polymerization hyperbranched polyvinyl acetate of embodiment one, polymerizing condition: solvent is 1, and 4-dioxane, polymerization temperature are 60 ℃, and the concentration of monomer VAc is 5.42molL ^-1[VAc] ₀: [ECTVA] ₀/ [AIBN] ₀=10: 1: 1.GPC elution curve figure according to ordinary method making gained hyperbranched polyvinyl acetate gets Fig. 4.

As shown in Figure 4, the GPC elution curve of resulting polymers all appears unimodal, and peak shape meets Gaussian distribution, shows that polymerization process does not produce tangible double activity center, and its molecular structure is in the controllable reaction.

Embodiment four, the chain extension of hyperbranched PVAc polymkeric substance

Get VAc (0.934g, 10.8mmol), hyperbranched PVAc polymkeric substance (2; Table 1) (119mg, 0.05mmol), AIBN (8.9mg; 0.05mmol) and 1mL 1; The 4-dioxane adds in the exsiccant ampere bottle, and logical argon gas 10min places the oil bath under the steady temperature (60 ℃) to react 2h the ampoule behind the tube sealing.After reaction finishes, take out tube sealing, with the cold water cooling, open tube sealing immediately,, pour in the sherwood oil and precipitate with the THF dissolving.Treat deposition fully, topple over and sherwood oil that polymkeric substance dries by the fire and causes constant mass, promptly obtains chain extension product (productive rate is 67%) in vacuum drying oven.

Contain the fragment of RAFT reagent through the polymer ends of RAFT polymerization process preparation, this fragment can further be used to regulate and control monomeric RAFT polymerization.Thereby, in the present embodiment, utilize the polymer P VAc for preparing down through the EVTAC regulation and control to be macromole RAFT reagent, having carried out VAc is that monomeric chain extension is realized, the GPC elution curve of polymkeric substance is as shown in Figure 5 before and after its chain extension.The result shows that behind chain extension, the molecular weight of polymkeric substance has been increased to 5700 by 2200, and the GPC curve before and after chain extension tangible displacement has taken place, and shows that the success of chain extending reaction is carried out.Yet, owing to there is the dead chain of part in the polymkeric substance, also possibly exists by AIBN in the chain extension process simultaneously and cause the VAc homopolymer that produces, thereby behind the chain extension, the MWD of polymkeric substance increases to 2.24 by original 1.30.

Embodiment five: the preparation of the nanometer gold under PVAc is stable

Get HAuCl ₄3H ₂O (100mg, 2.54 * 10 ^-4Mol) be dissolved in the 50mL THF, add PVAc (286mg, 2.17 * 10 ^-4Mol Mn=13200g/mol), stirs 24h.Subsequently, add Peng Qinghuana (113mg) aqueous solution 0.5mL, mixture vigorous stirring 4h.Product at 300000rpm spinning 40min, is collected solid product with ultracentrifuge, and uses THF washing three times, is scattered in the THF at last.

The TEM picture of the nanometer gold that obtains preparing according to routine techniques test, as shown in Figure 7, can find that from experimental result the nanometer gold that obtains when using hyperbranched PVAc as stablizer, its dispersiveness will obviously be better than the nanometer gold of linear PVAc under stablizing.

Embodiment six, the homopolymerization of ECTVA as shown in Figure 1

The homopolymerization process of RAFT reagent E CTVA is following: ECTVA (0.103g; 0.5mmoL); AIBN (1.70mg, 0.011mmol) with 5mL 1, the 4-dioxane adds in the exsiccant ampere bottle; Logical argon gas 10min places the oil bath under the steady temperature (60 ℃) to react preset time the ampoule behind the tube sealing.After reaction finishes, take out tube sealing, with the cold water cooling, open tube sealing immediately,, pour in the sherwood oil and precipitate with the THF dissolving.Treat deposition fully, topple over and sherwood oil that polymkeric substance dries by the fire and causes constant mass, promptly obtains polymer P ECTVA in vacuum drying oven.

Claims (2)

1. a RAFT reagent is characterized in that, the chemical structural formula of said RAFT reagent is as follows:

2. the preparation method of a hyperbranched polyvinyl acetate; With the vinyl acetate is monomer, and Diisopropyl azodicarboxylate is an initiator, constitutes RAFT polymerization (RAFT) system with RAFT reagent; With 1; The 4-dioxane is a solvent, in inert atmosphere, and the preparation hyperbranched polyvinyl acetate; It is characterized in that wherein said RAFT reagent is (2-oxyethyl group dithio perester radical) vinyl acetate, the chemical structural formula of said RAFT reagent is as follows:

Wherein, monomer: RAFT reagent: the mol ratio of initiator is 10～200: 1: 0.5～1; Said polymerization temperature is 40～120 ℃, and said polymerization time is 15～360 minutes.

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