Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F297/00—Macromolecular compounds obtained by successively polymerising different monomer systems using a catalyst of the ionic or coordination type without deactivating the intermediate polymer
  • C08F297/02—Macromolecular compounds obtained by successively polymerising different monomer systems using a catalyst of the ionic or coordination type without deactivating the intermediate polymer using a catalyst of the anionic type
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F293/00—Macromolecular compounds obtained by polymerisation on to a macromolecule having groups capable of inducing the formation of new polymer chains bound exclusively at one or both ends of the starting macromolecule
  • C08F293/005—Macromolecular compounds obtained by polymerisation on to a macromolecule having groups capable of inducing the formation of new polymer chains bound exclusively at one or both ends of the starting macromolecule using free radical "living" or "controlled" polymerisation, e.g. using a complexing agent
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F297/00—Macromolecular compounds obtained by successively polymerising different monomer systems using a catalyst of the ionic or coordination type without deactivating the intermediate polymer
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L53/00—Compositions of block copolymers containing at least one sequence of a polymer obtained by reactions only involving carbon-to-carbon unsaturated bonds; Compositions of derivatives of such polymers

Definitions

• the present invention relates to self- assembling compounds capable of forming a birefringent gel when added to an organic medium, such as an organic solvent or an organic monomer, in an amount of about 0.05% to about 2% by weight, based on the weight of the organic medium.
• a birefringent gel comprising the self -assembling compound and an organic monomer can be polymerized to form a birefringent polymer.
• the present invention also relates to a method of manufacturing an article from the birefringent gel or a birefringent melt of the birefringent polymer.
• a self -assembling compound is a block oligomer or polymer, containing a flexible block, a rigid block, and a dendritic block, wherein the bonds between the blocks are covalent bonds.
• amorphous polystyrene can be oriented by applying an external mechanical field.
• melt -drawn polystyrene fibers exhibit weak birefringence on the order of -0.02.
• flow- induced birefringence is not a permanent property of the polymer, and birefringence completely disappears when the melt -drawn polysty- rene fibers are heated above their glass transition temperature (T g ) .
• Birefringence is a property that is well known to persons skilled in the art of ordered materials, such as liquid crystals, and its measurement is a standard methodology used to determine whether a material exhibits long-range orientational or positional order.
• a material that exhibits birefringence is ordered, i.e., has a long-range molecular orientation or has do- mains of oriented molecules.
• Birefringence of a material is demonstrated using a bipolar microscope, wherein an ordered material rotates incident light from the microscope, and the light is transmitted through the material. Materials that lack order, i.e., are amorphous or glassy, scatter the incident light and appear dark when viewed through a bipolar microscope. In some systems, the observed transmit - ted light can be attributed, partially or completely, to the highly ordered, self -assembled DRC structure in the gels or polymers.
• the present invention is directed to self- assembling compounds, or molecules, that have the ability to form nanostructures, orient, or change the structure of organic media, including the coiled macromolecules of a typical amorphous, glassy poly- mer .
• the present compounds are linear, and form scaffold-like aggregates of a nanoscale dimension, in the form of ribbon, which impart order to otherwise disordered organic media, and improve the properties of the organic media.
• the present invention is directed to self-assembling compounds that improve the properties of polymeric materials, such as polystyrene, poly-
• ethyl methacrylate and other acrylic polymers, which are commercial polymers having numerous applications.
• modification of an organic medium, such as polystyrene or an organic solvent can be achieved using a compound of the present invention, termed a dendron-rodcoil or DRC compound, as an additive in small quantities to impart liquid crystal-like (LC) properties to organic media, like a polymer, and thereby impart improved optical, mechanical, and/or thermal properties to conventional amorphous and semi-crystalline polymers that otherwise have been unattainable.
• LC liquid crystal-like
• one aspect of the present invention is to provide a new and simple method of producing low-cost polymers having the highly advanced physical properties of expensive liquid crystalline polymers. In one embodiment, this aspect is achieved by imparting order to amorphous, glassy polymers using a present DRC compound. It also is possible to change the proper- ties of polymers that are semi-crystallme in nature, i.e., are not completely amorphous.
• a DRC compound of the present invention is a crys- talline material that is miscible with organic solvents and monomers. After monomer polymerization, the resulting polymer composite behaves like a homogeneous LC phase in that the polymer remains birefringent, i.e., is molecularly oriented, over a broad temperature range of up to 300°C (e.g., 200°C above the glass transition temperature of polystyrene) . This property allows a substantially greater orientation of the polymer during a melt-drawing process, including the manufacture of fibers, com- pared to that presently achieved using pure glassy polymers, such as polystyrene.
• one aspect of the present invention is to provide a compound having the ability to orient organic media, such as organic solvents and organic monomers.
• Another aspect of the present invention is to provide a compound having the ability to orient the macromolecular chains of an amorphous or semi- crystalline polymer and impart order, and, accord- ingly, improved properties, to the polymer.
• a compound of the present invention is a dendron-rodcoil , or DRC, which is a block oligomer or polymer having a branched block (dendron) , a rigid block (rod), and a flexible block (coil), wherein the bonds between the blocks are covalent bonds .
• DRC dendron-rodcoil
• a dendron-rodcoil, or DRC, compound can be depicted by the following three general structures: D- R - C D - C - R C - D - R ,
• D is the dendritic block
• R is the rod block
• C is the coil block
• bonds between the D, R, and C blocks are covalent bonds.
• Another aspect of the present invention is the formation of a birefringent gel, or a gel capable of rotating light, of an organic medium prepared by adding about 0.05% to about 2%, by weight, of a DRC compound to the organic medium, for example, an organic solvent or an organic monomer.
• An organic monomer is defined herein as a gaseous or liquid organic compound having a functional group capable of undergoing a polymerization reaction.
• the functional group typically is a carbon-carbon double or triple bond, but also can be an epoxy group, for example.
• An organic solvent is a liquid organic compound that lacks a functional group capable of undergoing a polymerization reaction.
• Another aspect of the present invention is the preparation of a birefringent polymer formed by polymerizing a birefringent gel comprising an organic monomer and a DRC material .
• the birefringent gel can further comprise metal ions to mineralize the birefringent polymer by forming inorganic materials te plated by the DRC assemblies.
• the birefringent gel also can contain a crosslmker, a polymerization initiator, and other optional ingredients to achieve specific properties in the final product .
• Yet another aspect of the present invention is to provide a method of manufacturing an article from a birefringent gel or a polymer prepared from a birefringent gel, comprising an organic monomer and a DRC compound.
• One method comprises melting the birefringent polymer to form a birefringent polymer melt, then forming the birefringent melt into the article, for example, drawing a fiber from the birefringent polymer melt to provide an optical fiber or molding the birefringent melt to form the article.
• an article can be formed by polymerizing the birefringent gel into a predetermined shape.
• Still another aspect of the present inven- tion is to provide a method of imparting order to an amorphous or semi -crystalline polymer by incorporating about 0.05% to about 2%, by weight of the polymer, of a DRC compound into the polymer.
• Another aspect of the present invention is to provide a mineralized, ordered polymer by introducing metal ions into a polymer containing about 0.05% to about 2%, by weight, of a DRC compound.
• Another aspect of the present invention is to admix the DRC compound with a gaseous monomer, like ethylene, then polymerize the resulting mixture to provide a polymer, or article prepared therefrom, having improved properties.
• a gaseous monomer like ethylene
• Fig. 1(A) contains photographs of birefringent dichloromethane gels containing a DRC com- pound of the present invention
• Figs. 1(B) and 1(C) contain photographs of polystyrene and poly (2-ethylhexyl methacrylate) containing a DRC compound and polystyrene and poly (2- ethylhexyl methacrylate) free of a DRC compound;
• Fig. 2 contains a molecular representation of a linear DRC compound of structural formula (1), and NMR spectra of the DRC compound in THF (a solution) and dichloromethane (a gel);
• Fig. 3 contains photographs of a small angle X-ray pattern of gel -derived polystyrene (A) and optical micrographs of the polystyrene taken between crossed polarizers showing birefringence at 100°C (B) and 250°C (C) ;
• Fig. 4 contains photographs of polystyrene containing 1%, by weight, DRC compound (1) (left) and 1%, by weight, of a diblock RC compound (right), and molecular representations of the DRC compound and RC compound, and aggregates of each;
• Fig. 5 contains X-ray diffraction patterns and optical micrographs of a pure polystyrene fiber (A, C, and E) and a polystyrene fiber containing 1%, by weight, DRC compound (1) (B, D, and F) ;
• Fig. 6 is a transmission electron micrograph of osmium tetroxide treated polystyrene con- taining 1%, by weight, DRC compound (1);
• Fig. 7 is a molecular representation of the bimolecular ribbon formed via self-assembly of linear DRC molecules of structural formula (1); and Fig. 8 contains plots of Herman's orientation factor (f) vs. draw (or deformation) ratios ( ⁇ ) for polystyrene (lower line) and polystyrene containing 1% by weight DRC compound (1) (higher line)
• the present invention is directed to self- assembling compounds that form a birefringent gel when added to an organic medium in an amount of about 0.05% to about 2%, by weight of the organic medium. If the organic medium is an organic monomer, the birefringent gel can be polymerized to form a birefringent polymer.
• the present invention therefore, is directed to improving the properties of polymers, like amorphous and semi -crystalline polymers, by inducing order in the polymers through incorporation of a small amount of a novel DRC compound into the poly- mer.
• the DRC compounds impart order to organic media, and convert amorphous and semi -crystalline polymers into composites that behave like liquid crystalline polymers, and, consequently, exhibit improved physical properties.
• the resulting compos- ites exhibit little or no microphase separation, and, surprisingly, retain birefringence in the melt form and behave in the melt form like a liquid crystalline material.
• modification of amorphous polystyrene using a present dendron- rodcoil compound as additive, in small quantities is specifically illustrated.
• the advantages achieved and the problems solved by the present invention include, for example: a) a very small amount of a DRC compound modifies a polymer and induces liquid crystalline- like (LC) order in the polymer; b) the DRC compound and the polymer components of the composite are sufficiently compatible to prevent the composite from undergoing appreciable microphase separation.
• the birefringent composite also can be oriented on a macroscopic level, thereby improv- ing tensile strength and other mechanical properties compared to amorphous polystyrene; and d) the composite remains highly birefringent, even at temperatures well above the T g , even when no external mechanical field is applied, because the birefringence of the composite is attributed to intrinsic order in the material .
• the present invention is directed to novel dendron-rodcoil (DRC) compounds that impart order to organic media at low concentrations of about 0.05% to about 2%, by weight of the media, and to polymers and articles of manufacture prepared from such ordered organic media.
• the novel DRC compounds are triblock oligomers or relatively low molecular weight polymers having a dendritic block (D) , a rod block (R) , and a coil block (C) , wherein bonds between the various blocks are covalent bonds.
• the dendritic block has a branched struc- ture.
• the rod block is rigid and unbrancned, whereas the coil block is flexible and unbranched.
• a DRC compound of the present invention has a general structural formula:
• D is the dendritic block
• R is the rod block
• C is the coil block
• the bonds joining the D, R, and C blocks are covalent bonds.
• Preferred embodiments of the present invention have the structure D-R-C.
• the DRC compounds have a tendency to aggregate, which is at- tributed to the rigid, rod block and flexible, coil block of the compound.
• the DRC compounds also resist packing in three dimensions because the branched structure of the dendritic block prevents stacking of DRC molecules.
• the DRC compounds therefore, associate to form a ribbon-like aggregate, as illustrated in Figs. 4 and 7, discussed hereafter.
• This ribbon-like aggregate of DRC molecules acts as a scaffold to impart order to organic media, such as organic solvents and organic mono- mers .
• the coil block, C is linear and flexible, and is an oligomer or polymer comprising one or more low molecular weight monomers.
• Block C has a weight average molecular weight (M w ) of about 200 to about 10,000, and preferably about 200 to about 5,000.
• M w weight average molecular weight
• block C has an M w of about 200 to about 2,000.
• the beneficial properties of the C block for example, helping provide a capability for the DRC compounds to aggregate, have a tendency to decrease as the M w of the C block increases. However, this decrease in beneficial properties is overcome by simultaneously increasing the M w of the R block. This M w effect of the C and R blocks is discussed in more detail hereafter .
• the C block is linear and unbranched, which allows the C blocks of DRC molecules to come in close proximity to one another (see Fig. 4) .
• the C block therefore, comprises monomers that preferably are unsubstituted, or substituted with small moieties, which allows individual DRC molecules to come in close proximity to form a molecular ribbon of DRC molecules, as illustrated in Fig. 7. Large substituent moieties on the monomers comprising the C block, which hinder aggregation of DRC molecules, typically are avoided.
• the branched D blocks prevent intimate contact and entanglement of the C blocks of neighboring DRC molecules (see Fig. 4) .
• the monomers comprising the C block therefore, can be any low molecular weight monomer that provides a flexible oligomer or polymer. If a hydrophobic C block is desired, the monomer can be ethylene, propylene, vinyl methyl ether, or a chlorinated or fluorinated vinyl monomer, e.g., vinyl chloride or vinylidene fluoride, for example.
• a hydrophilic C block can be prepared from a monomer like ethylene oxide or aziridine, for example.
• the C block also can contain reactive groups for availability in a subsequent reaction, for example, for entering into a polymerization reaction with an organic monomer after formation of a birefringent gel .
• a reactive C block is prepared from monomers like isoprene and butadiene, which provide a C block having carbon-carbon unsat- uration.
• Reactive groups also can be present m the C block as pendant substituents on the backbone of the C block.
• the C block can have hydroxy, ammo, carboxy, or cyano groups as pendant substituents.
• the C block also can have other small, nonreactive, pendant substituents, like methyl, ethyl, isopropyl, isopropenyl, halo (especially F or Cl) , and CF 3 , for example.
• the rod block, R is linear and rigid, and is an oligomer or polymer of a monomer that provides a rigid polymeric structure.
• Block R has an M w of about 200 to about 10,000, and preferably about 200 to about 5,000. To achieve the full advantage of the present invention, block R has an M w of about 200 to about 2,000.
• a function of the R block is to promote aggregation of DRC molecules to form a molecular ribbon of DRC molecules, as illustrated in Fig. 7. Aggregation and ribbon formation is adversely affected if the M w of C block is too large. However, this adverse affect can be overcome by increasing the length, i.e., M w , of the R block. It has been found that a ratio of C block monomer units to R block monomer units of about 2:1 to about 4:1, and preferably about 2.5:1 to about 3.5:1, provides preferred DRC compounds with respect to aggregation, forming a molecular ribbon, and imparting order to organic media.
• the R block comprises one or more monomers that provide a rigid polymer.
• One such monomer for example, is acetylene, which provides a rigid polymer having the general structure:
• the carbon-carbon double bonds of polyacetylene impart rigidity to block R, and provide reactive sites on the R block.
• monomers useful in providing the rigid R block are bifunctional phenyl monomers, bi- phenyl monomers having a functional group on each phenyl ring, and a compound having the structure
• A is (CH 2 ) n , O, S, or NH, wherein n is 1 or 2
• the Y groups are groups capable of undergoing a condensation reaction.
• the Y groups are independently selected from moieties such as -C0 2 H, -COCl, -C0 2 R (wherein R is Ci-C 4 alkyl) , -OH, -SH, -CONH 2 , -CONHR, -NH 2 , -NHR, -OSiR 3 , and similar condensable moieties well known to persons skilled in the art.
• Preferred Y groups are -C0 2 H, -OH, and -OSiR 3 .
• the R block is not branched. This feature allows the R blocks of the DRC molecules to come in close proximity to one another (Fig. 4), which assists aggregation because of ⁇ - ⁇ interactions between R blocks on neighboring DRC molecules.
• the dendritic block D is branched and is prepared by reacting functional groups on the R block and/or C block with a suitably functionalized compound to incorporate branches into the DRC compound.
• the branched D block prevents DRC compounds from stacking in three dimensions, but allows the DRC molecules to aggregate and form a ribbon.
• the D blocks of the DRC molecules aggregate to form a bimolecular species.
• the bimolecular species then aggregate to form DRC ribbons, or scaffolds.
• the compound used to incorporate branching into the DRC compound typically is a polyfunctional compound having a substituent capable of condensing with a substituent on the R or C blocks, and having additional substituents for further branching.
• a compound used to form the D block also can contain nonreactive substituents, like CF 3 .
• the D block is more hydrophilic than the R block, which assists in aggregation of the DRC compounds, for example by facilitating ⁇ - ⁇ interac- tions between aromatic rings in the R blocks of individual DRC molecules, and by promoting association of DRC molecules to form the bimolecular species by interactions such as hydrogen bonding through the D blocks.
• Increased hydrophilicity typically is achieved by having hydroxy substituents present on the D block.
• An example of a compound used to incorporate branching, i.e., a dendritic block, into a DRC compound is
• Y groups as defined above, are selected independently.
• the following synthetic scheme illustrates the preparation of a DRC compound of the present invention.
• synthesis of triblock DRC compound (1) illustrated in the following scheme begins with the preparation of an oligoisoprene block C by anionic polymerization. Functionali- zation of the flexible coil block C using ethylene oxide then is performed to provide a hydroxy-terminated oligoisoprene.
• Functionalized block C then is condensed with a carboxyl -substituted biphenyl com- pound to form an ester linkage under mild conditions (i.e., DIPC, diisopropylcarbodiimide; DPTS, 4-(N,N- dimethylamino) pyridinium-4 -toluenesulfonic acid; THF, tetrahydrofuran; HCl , hydrochloric acid, HF, hydrofluoric acid; RT, room temperature) .
• DIPC diisopropylcarbodiimide
• DPTS 4-(N,N- dimethylamino) pyridinium-4 -toluenesulfonic acid
• THF tetrahydrofuran
• HCl hydrochloric acid
• HF hydrofluoric acid
• RT room temperature
• the bi- phenyl compound also contained a tert-butyldimethyl- silyl protecting group, and deprotection then was performed at -78°C using tetrabutylammonium fluoride (TBAF) . Repetition of the esterification and depro- tection reactions yielded a diblock compound containing flexible oligoisoprene and rigid biphenyl segments, i.e., a diblock containing the C and R segments.
• the third D block of DRC compound (1) is dendritic, and is synthesized by reacting a protected form of an A 2 B-type monomer, i.e., 3,5-d ⁇ - hydroxybenzoic acid, with the diblock RC compound. Esterification and deprotection reactions illustrated hereafter provided the DRC compound of struc- tural formula (1) containing dendritic (D) , rod (R) , and coil (C) segments, or blocks.
• the flexible oligoisoprene C block of DRC compound (1) contains, on average, about 9 monomeric isoprene units, and is structurally diverse, primarily containing the 3,4 addition product of isoprene.
• the C block imparts solubility to DRC compound (1), thereby allowing a self-assembly process to occur in solution or m the melt.
• the geometry of the dendron block D, and the coil block C facilitate formation of one -dimensional self-assembled struc- tures, or scaffolds, i.e., ribbons of bimolecular species of DRC molecules.
• the bulki- ness of the dendritic block D relative to rod block R prevents the formation of three-dimensional assemblies, i.e., stacks of DRC ribbons.
• the essentially identical aromatic rod-dendron blocks of DRC compound (1) strongly drive aggregation through nonco- valent ⁇ - ⁇ interactions.
• the four hydroxy groups located on the periphery of dendritic block D provide an additional driving force for self-assembly of DRC compound (1) molecules through the formation of hydrogen bonds between DRC molecules.
• Magnesium sulfate (MgS0 4 ) was used to dry all organic solutions during work-up procedures.
• the silica used for flash chromatography was Silica Gel 60 (230-400 mesh) , available from EM Sciences. 1 H NMR spectra were recorded in THF-d 6 or
• Mass spectrometry was performed by the Mass Spectroscopy Laboratory at the University of Illinois, Urbana-Champaign, IL. High resolution field desorption mass spectra were collected on a Micromass 70-VSE spectrometer operating at 8 KV acceleration voltage and 4 KV extraction plate voltage. Matrix assisted laser desorption ionization (MALDI) mass spectra were obtained on a VG TofSpec spectrometer using dithranol silver tri- fluoroacetate as a matrix. Elemental analyses were performed by the University of Illinois Microanalyt- ical service Laboratory using a Perkin-Elmer Model
• the esterification reactions were performed on a scale of about 4 to about 12 grams (g) .
• a mixture of the diblock R-C rodcoil (1 equivalent), 3 , 5-b ⁇ s ( tert-butyldimethyl- silyloxy) benzoic acid (1 equivalent), and DPTS (1 equivalent) was dissolved in methylene chloride (CH 2 C1 2 ) , and the resulting mixture was stirred under nitrogen.
• DIPC (1 equivalent) was added to the stirred mixture via syringe, and the reaction was allowed to proceed, with stirring, for 3 hours.
• Benzene (100 mL) and THF (20 mL) were added to a flask, followed by the addition of n- butyl lithium (n-BuLi, 1 equivalent), and finally the addition of isoprene (9 equivalents) .
• the re- suiting reaction mixture was stirred for 30 minutes, then quenched by bubbling ethylene oxide through the solution for about 15 minutes, followed by addition of 10 mL (milliliters) of 3 N HCl/THF (1/2 weight ratio) .
• the solvents then were removed by rotatory evaporation.
• the diblock polymer was prepared from esterification of the hydroxy- functionalized isoprene oligomer and Reactant B (4 - ert-butyld ⁇ methyl- s ⁇ lyloxy-4 -biphenylcarboxylic acid) by the above- described general esterification procedure.
• the reaction product was purified by flash chromatography by eluting with CH 2 C1 2 to yield a silyl-protected diblock RC polymer as a colorless liquid. Yield: 69%.
• a diblock RC polymer was prepared from the silyl protected diblock RC polymer by the above- described general silyl deprotection method, and was purified by flash chromatography by eluting with 5% THF/CH 2 C1 2 to yield a diblock RC polymer as a colorless liquid. Yield: 95%.
• a third biphenyl compound was added to complete the synthesis of diblock RC polymer by esterifymg the above compound.
• the resulting esterification product was purified by flash chromatography by eluting with 7% THF/CH 2 C1 2 to yield a white solid. Yield: 76%.
• the diblock RC prepared above was reacted with Reactant D (3 , 5-bis ( ert-butyldimethylsilyl- oxy) benzoic acid), by the above-described general esterification method, and the resulting product was purified by flash chromatography by eluting with 7% THF/CH 2 C1 2 to yield a white solid. Yield: 89%.
• the above silyl protected product was silyl deprotected by the above-described general silyl deprotection method, and resulting reaction product was purified by flash chromatography by eluting with CH 2 C1 2 and gradually increasing to 10% THF/CH 2 C1 2 to yield the DRC compound of structural formula (1) as a white solid. Yield: 78%.
• the DRC compounds of the present invention have the ability to impart order to organic media, for example, organic solvents and organic monomers. Ordering of the organic solvent or monomer is demonstrated by the formation of a birefringent gel by the addition of about 0.05% to about 2%, by weight of the organic media, of a DRC compound to the organic media.
• the birefringent gel can be subjected to a polymerization reaction to form a birefringent polymer.
• the birefringent polymer can be melted and retain its birefringence, then the birefringent melt can be formed into a birefringent article of manufacture, like a fiber.
• the birefringent polymer retains its birefringent property even after several melt cycles, and, in each cycle, the melt exhibits liquid crystalline-like properties. This is a totally unexpected property for a polymer composite comprising 98% or greater polystyrene.
• a birefringent gel contain- mg DRC molecules and an organic monomer can be prepared in a desired, predetermined shape. This birefringent gel then can be subjected to polymerization conditions to provide a birefringent article of manufacture.
• a birefringent gel can be spun and formed into a fiber after polymerization, or the birefringent gel can be prepared in a form, which, after polymerization, provides an article of manufacture the shape of the form.
• the DRC compound of structural formula (1) was dissolved in dichloromethane to form a dilute 1 weight % solution of DRC compound (1) .
• the resulting solution undergoes spontaneous gelation to form a soft solid having a blue-violet hue.
• the DRC compound of structural formula (1) and dichloromethane were added to a capped vessel, and the resulting mixture was heated to 70-80°C.
• a viscous, blue solution formed, which gelled within several minutes at 70°C.
• the vessel then was cooled to room temperature.
• the resulting gel was optically transparent and had blue-violet color. Neither phase separation nor precipitation was observed in the gels, and the gels remained stable for extended periods of time.
• Fig. 1A contains photographs of a series of inverted vials showing the formation of CH 2 C1 2 gels containing 0.3% to 1.5%, by weight, DRC compound, and showing the flow of a gel prepared using 0.2 weight % of DRC compound (1) in dichloromethane. The % of DRC compound in each gel is indicated on the vials. All the gels in Fig.
• Fig. 1A were birefringent when observed under cross polarizers in an optical microscope, and most importantly, upon heating, melting of the gel is not observed in a sealed vessel, even at temperatures well above the boiling point of the solvent.
• the gel structure illustrated in Fig. 1 is thermally irreversible, con- trary to most, if not all, organogels. See, Y.C. Lin et al . , J. Am. Chem . Soc , 111 , 5542 (1989); P. Terech et al . , J. Phys . Chem . , 99, 9558 (1995); P. Terech et al . , Chem . Rev. , 97 , 3133 (1997); W.Q.
• Birefringent gels also can be formed by adding a DRC compound to an organic monomer in an amount of about 0.05% to about 2%, by weight of the organic monomer.
• the organic monomer can be a liquid or a gas.
• the DRC compound is added to the organic monomer in an amount of about 0.1% to about 1.5%, and preferably about 0.25% to about 1%, by weight.
• Birefringent gels containing 0.3% to 2%, by weight of the DRC compound have sufficient strength to support their own weight .
• a birefringent gel can be formed by introducing a DRC compound (0.2 g) and styrene (20 g) into a capped vessel, followed by heating the vial in an oil bath for 10-15 minutes at about 100°C until all the DRC compound was dissolved. The resulting solution was rapidly cooled to room temperature, and the birefringent gel formed within several minutes . The gel was aged for one day at room temperature, then the capped vial was placed in a heating chamber at 110 °C under nitrogen atmosphere for 48 hours. Under these conditions, the soft gel was transformed into solid polymer composite, which had the characteristic blue-violet hue of a birefringent material and was transparent to visible light.
• birefringent gels containing a DRC compound and styrene are heated to about 100°C, polymerization of styrene occurs without any indication of a disruption of the gel structure, and the resulting hard polymer composite retains the same blue-violet hue of the gel.
• the birefringent polystyrene was examined by size exclusion chromatography (SEC) , which indicated an average M w of about 240,000, and a relatively low polydispersity index of about 1.9.
• Fig. 1 (B and C) contain photographs of three polystyrene specimens, each polymerized under the same conditions.
• Fig. 1(B) contains photographs of free-standing specimens.
• Fig. 1(C) contains photographs of the three specimens laying on a table.
• the specimen on the left of Fig. 1 (B and C) is pure polystyrene.
• the middle specimen is a gel -derived polystyrene containing 1%, by weight, of the DRC compound of structural formula (1) .
• the right specimen is a gel-derived from poly (2-ethylhexyl methacrylate) , a rubber-like material at room temperature, containing 1%, by weight, of the DRC compound of structural formula (1) .
• the photographs of Fig. 1 (B and C) reveal the optical transparency of all samples, and a wavelength filtering effect at the bottom of the gel -derived samples, which is not observed in the pure polystyrene sample.
• the poly- styrene and poly (2-ethylhexyl methacrylate) containing the DRC are birefringent, and thus have retained some order after polymerization.
• the polystyrene composites containing the DRC compound (1) exhibited birefringence under crossed polarizers and gave small angle X-ray (SAXS) peaks with a primary d- spacmg of 100 A corresponding to double the length of the DRC compound of structural formula (1) .
• SAXS small angle X-ray
• Fig. 2 contains NMR spectra of a THF solution of the DRC compound of structural formula (1) (top) and of the DRC compound (1) in a dichloromethane gel (bottom) .
• a molecular representation of the DRC compound of structural formula (1) is shown on the right of Fig. 2.
• Fig. 2 shows the disappear- ance of aromatic resonances in the gel formed in dichloromethane (bottom) .
• the aromatic resonances are clearly resolved the NMR spectra of a solution of DRC compound (1) m tetrahydrofuran (top) .
• All three types of protons (aromatic, vinyl, and aliphatic) generate signals in THF solutions because the DRC molecules can freely rotate in the absence of aggregation.
• the NMR signals that disappeared after gelation correspond to aromatic protons from both the dendritic (D) and rod (R) segments of DRC compound (1) .
• the absence of these NMR resonances indicates that a drastic decrease in motion has occurred, which results in nonaveragmg of magnetic anisotropies .
• protons from the flexible oligoisoprene coil (C) segment still gener- ate intense, but somewhat broadened, signals after gelation. Similar observations were made in NMR spectra of styrene-based gels of DRC compound (1) . Based on such evidence, it was concluded, but not relied upon herein, that aggregation of DRC mole- cules is mediated by aromatic units, and that aggregation is responsible for the birefringent gelation of nonpolar solvents, like CH 2 C1 2 . In contrast, oligoisoprene segments (blocks C) retain their rotational freedom in what is theorized to be a solvated self -assembled structure.
• Fig. 3(A) contains a small angle X-ray pattern of a gel -derived polystyrene containing 1 weight % of DRC compound (1)
• Fig. 3 (B and C) contain optical micrographs between crossed polarizers showing the birefringent texture of polystyrene containing 1 weight % DRC compound (1) at 100°C (B) and 250°C (C) . If the polymer did not exhibit birefringence, Fig. 3(B) and Fig. 3(C) would appear black.
• Polarized optical microscopy at elevated temperatures revealed a texture similar to that observed in liquid crystals and which was present until the isotropization point was reached at 310°C.
• the bright optical texture observed at the glass transition temperature (100°C) of polystyrene indicates a highly anisotropic medium (Fig. 3B) .
• Fig. 3B highly anisotropic medium
• the homogeneity of the optical texture shows the absence of macrophase separation.
• the self -assembled structure is suggested to be an aggregation of DRC molecules, in the form of ribbons of bimolecular DRC species.
• diblock RC molecules shows frustrated packing the x-y plane due to the presence of bulky dendritic fragments.
• the close packing of the rod segments in diblock RC molecules (right in Fig. 4) is not prevented, which is why diblock RC molecules can strongly aggregate via ⁇ - ⁇ stacking of biphenyl units forming two-dimensional assemblies within x-y plane. It has been suggested that a frustrated long-range aggregation in two dimensions among dendritic molecules plays an important role m this very unexpected behavior.
• Small angle X-ray scattering of the polymerized birefringent gel also reveals a Bragg reflection with characteristic spacing of about 10.7 nm (Fig. 3A) .
• the force field minimized length of average-sized DRC molecules is about 6.5 nm (nanometers), and, therefore, the d-spacmg observed is consistent with bilayer packing of dendron rodcoils to form a bimolecular species .
• the observed spacing is consistent with head-to-head (i.e., D block to D block) packing of DRC molecules (Fig. 4), and mter- digitation of the flexible oligoisoprene C block segments.
• This bilayer is theorized to be the main structural species, and also is the fundamental bi- molecular species causing medium gelation.
• gels formed dichloromethane and styrene monomer do not produce any small angle diffraction.
• DRC molecules are aggregated in the gel state. This suggests that in the gel, bimolecular species on the order of 10 nm form long separated strings, and, therefore, lack the neces- sary coherence to observe X-ray diffraction.
• Fibers were drawn from a birefringent melt of the birefringent polymer, and surprisingly, the solid fiber not only maintained its birefringence, but also revealed macroscopic orientation of the molecular DRC scaffold by small angle X-ray diffraction (Figs. 5D and 5F) . Similar fibers drawn from a pure polystyrene melt show almost no birefringence, and do not reveal evidence of molecular orientation by small angle X-ray diffraction (Figs. 5C and 5E) . Overall, Fig.
• 5 contains a wide-angle X-ray diffraction pattern collected from a pure polystyrene fiber (A) and a fiber of polystyrene containing 1 weight % of DRC compound (1) (B) ; small-angle X-ray diffraction pattern collected from the pure polystyrene fiber (C) and the fiber of scaffolded polystyrene containing 1 weight % of DRC compound (1) (D) ; and an optical micrograph between crossed polarizers showing the melt -drawn fibers of pure polystyrene (E) and a polystyrene containing 1 weight % of DRC compound (1) (F) .
• Wide angle x-ray patterns also were analyzed to estimate the extent of polystyrene chain orientation samples containing a DRC compound of the present invention, and samples free of a DRC compound.
• Hermans orientation factor f Hermans orientation factor f
• f (l/2 ) (3 (cos 2 ⁇ ) - 1 ) wherein ⁇ is the angle between the fiber axis and chain segments and (cos 2 ⁇ ) is the average cosine squared of ⁇ , was calculated.
• the calculation of f revealed a significantly higher degree of orienta- tion for polystyrene chains DRC containing polystyrene at all draw ratios, ⁇ , used. This unexpected result is illustrated in Fig. 8, wherein the lower plot relates polystyrene, and the higher plot (i.e., a greater f) relates to polystyrene contain- ing 1% by weight of DRC compound (1) of the present invention.
• Ultramicrotomed sections of the polymerized birefringent gel were analyzed by transmission electron microscopy (TEM) after staining with osmium tetroxide (OsO .
• TEM samples were cut using a
• Riechert-Jung Ultracut S microtome equipped with a diamond knife at an average thickness of 75-80 nm.
• the sections were transferred to holey carbon coated TEM grids, and then stained with Os0 4 vapors for 2 hours, which selectively stains the unsaturated double bonds in the oligoisoprene C block of the DRC compound .
• Fig. 6 is a typical electron micrograph of a cross section of a polymerized birefringent gel containing a small percentage of divinylbenzene to crosslink the polymer matrix. Small amounts of di- vinylbenzene crossl ker, typically about 2 weight % by weight of the monomer, were used to prepare the samples investigated by TEM. Divinylbenzene was used to maximize conversion of styrene monomer to polymer, and to eliminate contributions of residual styrene to the staining contrast.
• Fig. 6 therefore, is a transmission electron micrograph, at high magnification, of a thin film (75 nm thick) ultramicrotomed from a polystyrene composite containing 1 weight % of DRC compound (1) showing a domain of DRC molecules (A) , a matrix of polystyrene (B) , and circular arched features (C) which are theorized to be bimolecular strands of DRC molecules passing through the polystyrene matrix perpendicular to the cutting plane.
• the contrast in the TEM of Fig. 6 is produced by osmium tetroxide which selectively stains carbon-carbon double bonds m the oligoisoprene segment of the DRC molecules.
• the elongated dark feature labeled A in Fig. 6 comprises thin black lines, which are theorized to be a domain of aggregated DRC molecules. Oligoisoprene blocks in the DRC molecules are the only stainable segments of the polymers, and, therefore, the light gray background B is the continuous matrix of crosslinked polystyrene.
• the spacing of dark lines within feature A is roughly 10 nm, which is commensurate with the characteristic d-spacmg observed m X-ray experiments.
• the image in Fig. 6 confirms the bimolecular ar- rangement of DRC molecules in the polymer matrix.
• the oligoisoprene segments are spatially isolated by a stain-resistant region that appears darker than the matrix, suggesting that this region contains densely-packed biphenyl segments.
• the lack of continuity of the black lines implies that the aggregated DRC molecules meander through the matrix in three dimensions.
• Fig. 6 One important feature of the image in Fig. 6 is the small, circularly-shaped dark objects dispersed throughout and labeled as C. If an arbitrary slice is cut from a random three-dimensional network, then some strands pierce the cross section and others lie in the plane of the cross section. It is theorized that the circular features in the image are bimolecular strands of DRC molecules passing perpendicular to the cutting plane. Furthermore, the circular features have modes of darkness suggesting the strands do not have cylindrical symme- try. The distance between the arcs in these features again is 10 nm, which matches the observed spacing in A domains.
• Fig. 7 sets forth a schematic molecular representation of the bimolecular ribbon formed by self -assembly of DRC molecules. Fig. 7 illustrates the nanoscaffold and shows how nanoscaffold dimensions can be explained from the identity of the DRC molecules in the nanoscaffold.
• the area of contact of scaffold material with the polymer matrix is estimated to be about 16 m 2 /cm 3 in a system containing 1 weight % of the self-assembling DRC compound in the polymer matrix.
• This estimate is based on first calculating the total number of DRC molecules of structural formula (1) contained in 1 cm 3 of the styrene gel on the basis of the average molecular weight of DRC determined by mass spectrometry (i.e., about 1700 g/mole) .
• This area of contact corresponds to a length of DRC nanoscaffold of about 8 x 10 5 km/cm 3 .
• polystyrene and scaffolded polystyrene i.e., containing 1 weight % DRC molecules
• the X-ray samples were cut from the central part of the frozen fibers. The orientation in all tested samples was homogeneous over a multiple length scale of the scattering volume. The diameter of the X-ray beam was 0.5 mm, which is significantly smaller than the characteristic size of the central sample area (about 3 mm) .
• the reflections correspond in real space to the mtermolecular separation of about 9 angstroms between polystyrene chains (see Fig. 5B) .
• This effect is not observed when a fiber is drawn from molten polystyrene under the same conditions (Fig. 5A) . It is, therefore, theorized that the observed birefringence the scaffolded polystyrene has contributions from both the polystyrene matrix and the small weight percent of self -assembling DRC molecules .
• DRC compound of structural formula (1) (10 mg) , cadmium nitrate (20 mg of 0.1M THF solution) , and dichloromethane (1 g) were placed in a capped vial, and heated at 70°C until all the solid material was dissolved. The resulting solution was cooled to room temperature, and the gel was aged for 6 hours . The gel then was exposed to a stream of hydrogen sulfide. Diffusion of hydrogen sulfide into the gel was carried out from the top of the vial at room temperature for 1 hour at a flow rate 5 m /min. The conversion of cadmium nitrate to cadmium sulfide was accompanied by appearance of a green-yellow color.
• a present DRC molecule can be added to the following nonlimit g monomers to provide a birefringent gel, and, ultimately, a birefringent polymer: methyl methacrylate, 2-ethylhexyl methacrylate, acrylic acid, methacrylic acid, acrylonit ⁇ le, ethacrylic acid, ⁇ -chloroacrylic acid, -cyanoacrylic acid, /3-methylacryl ⁇ c acid (crotonic acid) , -phenylacrylic acid, 5-acryloxy- propionic acid, sorbic acid, ⁇ -chlorosorbic acid, angelic acid, c namic acid, p-chlorocmnamic acid, vinyl sulfonic acid, allyl sulfonic acid, vinyl toluene sulfonic acid, styrene sulfonic acid, acrylic and methacrylic sulfonic acids, such as sulfoethyl acrylate,
• R 1 represents hydrogen or a ⁇ 0 alkyl group
• the phenyl ring is optionally substituted with one to four C 4 alkyl or hydroxy groups, ethyl (meth) acrylate, isopropyl (meth) acrylate , n- propyl (meth) acrylate, n-butyl (meth) acrylate , C, 1S - alkyl (meth) acrylates including, but are not limited to, isobutyl, pentyl , isoamyl, hexyl, 2-ethylhexyl, cyclohexyl, decyl, isodecyl, benzyl, lauryl, isobornyl, octyl, and nonyl (meth) acrylates , -methyl- styrene, /J-methylstyrene , p-methylstyrene, t-butyl
• monomers that are a gas at 30°C and atmospheric pressure also can be used.
• gaseous monomers include, but are not limited to, C 2 -C 3 hydrocarbons and halo- genated C 2 -C 5 hydrocarbons containing one or more carbon-carbon double bonds and/or triple bonds.
• Nonlimitmg examples of gaseous monomers that can be used with DRC molecules of the present invention to provide birefringent articles of manufacture m- elude are not limited to, ethylene, propylene, butene, acetylene, butadiene, ethylene oxide, buta- diyne, isopropenyl chloride, vinyl chloride, lsobu- tylene, vinyl bromide, v ylidene fluoride, vinyl fluoride, propyne , butyne , tetrafluoroethylene , and similar alkene, alkynes, and halogenated derivatives thereof, and mixtures thereof.
• a birefringent gel containing a DRC compound and an organic monomer typically is polymer- ⁇ zed to form a birefringent polymer.
• the polymerization is a free radical polymerization performed on the neat birefringent gel, or performed by suspension or emulsion polymerization techniques known to persons skilled in the art.
• Polymerization of the birefringent gel can be performed in the presence of a polymerizable crossl ker, conventionally a polyunsaturated organic monomer.
• crosslinking polyvinyl monomers include, but are not limited to, poly- acrylic (or polymethacrylic) acid esters represented by the following formula (I); and bisacrylamides , represented by the following formula (II) .
• X is ethylene, propylene, tnmethylene, cyclohexyl, hexamethylene, 2 -hydroxypropylene, - (CH 2 CH 2 0) P CH 2 CH,- , or
• p and r are each an integer 5 to 40, and k is 1 or 2;
• crosslinking monomers include, but are not limited to, 1 , 4 -butanediol diacrylate, 1 , 4-butaned ⁇ ol dimethacrylate, 1,3-butylene glycol diacrylate, 1,3-butylene glycol dimethacrylate, diethylene glycol diacrylate, diethylene glycol dimethacrylate, ethoxylated bisphenol A diacrylate, ethoxylated bisphenol A dimethacrylate, ethylene glycol dimethacrylate, 1 , 6-hexaned ⁇ ol diacrylate, 1 , 6-hexaned ⁇ ol dimethacrylate, neopentyl glycol dimethacrylate, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, triethylene glycol diacrylate, triethylene glycol dimethacrylate, t ⁇ - propylene glycol diacrylate, tetraethylene glycol diacrylate, tetraethylene glycol dimethacrylate, dipenta
• the crosslinking monomer typically is admixed with the organic monomer prior to gelling the organic monomer with a DRC compound.
• a polymerization initiator can be added to the organic monomer prior to gellation to facilitate subsequent polymerization of the gel.
• the initiator can be a photoinitiator, a thermal initiator, or other type of initiator known to persons skilled in the art, typically in an amount of about 0.1% to about 5%, by weight of the organic monomers.
• the DRC compounds of the present invention have the unexpected ability to form birefringent gels when added to an organic medium, like an organic solvent or organic monomer.
• the birefringent organic monomer gel can be polymerized to form a birefringent polymer.
• a melt of the birefringent polymer also is birefringent, and birefringence is maintained even after melting the birefringent polymer several times. It also is envisioned that a birefringent polymer can be obtained by adding a DRC compound of the present invention to a melt of a polymer.
• a birefringent polymer melt then can be formed into an article of manufacture, for example, by drawing the birefrmg- ent melt into a fiber to provide an optical fiber that is macroscopically oriented and capable of transmitting light beams.

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