Polymerization of o‐quinodimethanes. IV. Radical polymerization of 1‐cyano‐o‐quinodimethane in the presence of TEMPO

The radical polymerization behavior of 1‐cyano‐o‐quinodimethane generated by thermal isomerization of 1‐cyanobenzocyclobutene in the presence of 2,2,6,6‐tetramethylpiperidine‐N‐oxide (TEMPO) and the block copolymerization of the obtained polymer with styrene are described. The radical polymerization of 1‐cyanobenzocyclobutene was carried out in a sealed tube at temperatures ranging from 100 to 150 °C for 24 h in the presence of di‐tert‐butyl peroxide (DTBP) as a radical initiator and two equivalents of TEMPO as a trapping agent of the propagation end radical to obtain hexane‐insoluble polymer above 130 °C. Polymerization at 150 °C with 5 mol % of DTBP in the presence of TEMPO resulted in the polymer having a number‐average molecular weight (M_n ) of 2900 in 63% yield. The structure of the obtained polymer was confirmed as the ring‐opened polymer having a TEMPO unit at the terminal end by ¹H NMR, ¹³C NMR, and IR analyses. Then, block copolymerization of the obtained polymer with styrene was carried out at 140 °C for 72 h to give the corresponding block copolymer in 82% yield, in which the unimodal GPC curve was shifted to a higher molecular weight region. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3434–3439, 2000     

Anionic polymerization of N,N‐dialkyl‐2‐methylenebut‐3‐enamide: Effect of alkyl substituents on polymerization behavior

Anionic polymerizations of three 1,3‐butadiene derivatives containing different N,N‐dialkyl amide functions, N,N‐diisopropylamide (DiPA), piperidineamide (PiA), and cis‐2,6‐dimethylpiperidineamide (DMPA) were performed under various conditions, and their polymerization behavior was compared with that of N,N‐diethylamide analogue (DEA), which was previously reported. When polymerization of DiPA was performed at ?78 °C with potassium counter ion, only trace amounts of oligomers were formed, whereas polymers with a narrow molecular weight distribution were obtained in moderate yield when DiPA was polymerized at 0 °C in the presence of LiCl. Decrease in molecular weight and broadening of molecular weight distribution were observed when polymerization was performed at a higher temperature of 20 °C, presumably because of the effect of ceiling temperature. In the case of DMPA, no polymer was formed at 0 °C and polymers with relatively broad molecular weight distributions (M_w/M_n = 1.2) were obtained at 20 °C. The polymerization rate of PiA was much faster than that of the other monomers, and poly(PiA) was obtained in high yield even at ?78 °C in 24 h. The microstructure of the resulting polymers were exclusively 1,4‐ for poly(DMPA), whereas 20–30% of the 1,2‐structure was contained in poly(DiPA) and poly(PiA). © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3714–3721, 2010     

Chain‐growth condensation polymerization of 4‐aminobenzoic acid esters bearing tri(ethylene glycol) side chain with lithium amide base

Chain‐growth condensation polymerization of p‐aminobenzoic acid esters 1 bearing a tri(ethylene glycol) monomethyl ether side chain on the nitrogen atom was investigated by using lithium 1,1,1,3,3,3‐hexamethyldisilazide (LiHMDS) as a base. The methyl ester monomer 1a afforded polymer with low molecular weight and a broad molecular weight distribution, whereas the polymerization of the phenyl ester monomer 1b at ?20 °C yielded polymer with controlled molecular weight (M_n = 2800–13,400) and low polydispersity (M_w/M_n = 1.10–1.15). Block copolymerization of 1b and 4‐(octylamino)benzoic acid methyl ester ( 2 ) was further investigated. We found that block copolymer of poly 1b and poly 2 with defined molecular weight and low polydispersity was obtained when the polymerization of 1b was initiated with equimolar LiHMDS at ?20 °C and continued at ?50 °C, followed by addition of 2 and equimolar LiHMDS at ?10 °C. Spherical aggregates were formed when a solution of poly 1b in THF was dropped on a glass plate and dried at room temperature, although the block copolymer of poly 1b and poly 2 did not afford similar aggregates under the same conditions. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1357–1363, 2010     

Cationic polymerization of L,L‐lactide

Cationic bulk polymerization of L ,L‐ lactide (LA) initiated by trifluromethanesulfonic acid [triflic acid (TfA)] has been studied. At temperatures 120–160 °C, polymerization proceeded to high conversion (>90% within ～8 h) giving polymers with M_n ～ 2 × 10⁴ and relatively high dispersity. Thermogravimetric analysis of resulting polylactide (PLA) indicated that its thermal stability was considerably higher than the thermal stability of linear PLA of comparable molecular weight obtained with ROH/Sn(Oct)₂ initiating system. Also hydrolytic stability of cationically prepared PLA was significantly higher than hydrolytic stability of linear PLA. Because thermal or hydrolytic degradation of PLA starting from end‐groups is considerably faster than random chain scission, both thermal and hydrolytic stability depend on molecular weight of the polymer. High thermal and hydrolytic stability, in spite of moderate molecular weight of cationically prepared PLA, indicate that the fraction of end‐groups is considerably lower than in linear PLA of comparable molecular weight. According to proposed mechanism of cationic LA polymerization growing macromolecules are fitted with terminal ? OH and ? C(O)OSO₂CF₃ end‐groups. The presence of those groups allows efficient end‐to‐end cyclization. Cyclic nature of resulting PLA explains its higher thermal and hydrolytic stability as compared with linear PLA. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2650–2658, 2010     

Thermal polycondensation of sugar fluoride to form highly branched polysaccharide

Sugar fluorides were found to undergo powder‐to‐powder polycondensation without any catalyst at 110–160 °C under vacuum, giving highly branched polysaccharides (Conv. = 40–95%, M_w = 1400–20,000). The cross‐polarized optical microscopy at 110 °C disclosed that the crystal shape of α‐glucosyl fluoride ( FGlc ) was unchanged throughout the polymerization in spite of producing the amorphous polymer ( Poly‐FGlc ). The solid‐state post polymerization of Poly‐FGlc (M_w: 2700) at 180 °C increased the higher molecular weight (M_w: 8900). The product polysaccharide was per‐O‐methylated and subjected to structure analyses. Acid‐hydrolysis, which gave a variety of the partially O‐methylated monosaccharides, suggested that the product polysaccharides had a highly branched structure consisting of all of the possible glycosidic linkages. MALDI‐TOF mass analysis revealed that the 1,6‐anhydride terminal unit was formed and participated to the polymerization. Interestingly, α‐maltosyl fluoride hydrate ( FMal·H ₂ O ) was polymerized at the lower temperature (100 °C) than the anhydrate ( FMal ), which required 160 °C for the polymerization. They produced different structure polymers even from the same monomer. The polymer from the former consisted of the disaccharide‐repeating unit, while the repeating unit of the polymer from the latter was the monosaccharide, which was formed by the acetal exchange reaction. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3851–3860, 2007     

Polymerization of o‐quinodimethanes. III. Polymerization of o‐quinodimethanes bearing electron‐withdrawing groups formed in situ by thermal ring‐opening isomerization of corresponding benzocyclobutenes

The substituent effect on the radical polymerization of o‐quinodimethanes, generated by thermal isomerization of benzocyclobutenes, was investigated. Polymerizations of three benzocyclobutenes bearing electron‐withdrawing groups were studied, namely 1‐cyanobenzocyclobutene (1), 1‐chlorobenzocyclobutene (2), and 1‐bromobenzocyclobutene (3). While radical polymerizations of 2 and 3 did not afford any polymer, radical polymerization of 1 afforded n‐hexane‐insoluble polymer(M_n = 5000) in moderate yields at temperatures above 120°C. The structure of the obtained polymer was confirmed to be a ring‐opened polymer(4) by IR, ¹H‐, and ¹³C‐NMR. The yield of the polymer increased with an increase in the initiator concentration. The polymer yield reported in this paper is higher than those of benzocyclobutenes bearing electron‐donating groups, reported previously by the authors. The semi‐empirical molecular orbital calculation supported the contribution of ring‐opening polymerization of spiro‐compounds, rejecting the possibility of 1,4‐polymerization. Lastly, radical copolymerizations of 1 with various comonomers were also performed to obtain the corresponding copolymers. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1555–1563, 1999     

Synthesis of sulfur‐containing hyperbranched polymers by the bisthiolation polymerization of diethynyl disulfide derivatives

The reaction of phenyl propynyl ether and diphenyl disulfide in the presence of 1 mol % tetrakis(triphenylphosphine)palladium as a model reaction of the polymerization of bis(4‐prop‐2‐ynyloxyphenyl) disulfide ( 1a ) gave a Z‐substituted dithioalkene. No E‐substituted dithioalkene was formed in this reaction. The palladium‐catalyzed bisthiolation polymerization of a diethynyl disulfide derivative, 1a , in benzene, was carried out to give a hyperbranched polymer ( 5a ) containing a Z‐substituted dithioalkene unit after reaction for 4 h at 70 °C. From the gel permeation chromatography analysis (chloroform, PSt standards), the number‐average and weight‐average molecular weights of 5a were found to be 8,100 and 57,000, respectively. The structure of 5a was confirmed by ¹H and ¹³C NMR spectra. The obtained polymer was soluble in common organic solvents such as benzene, acetone, and CHCl₃. Polymerization for more than 5 h gave insoluble products. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3580–3587, 2007     

Vinyl addition polymerization of norbornene using cyclopentadienylzirconium trichloride activated by isobutyl‐modified methylaluminoxane

Norbornene polymerization using the commercially available and inexpensive catalyst system, cyclopentadienylzirconium trichloride (CpZrCl₃) and isobutyl‐modified methylaluminoxane (MMAO), were carried out over a wide range of polymerization temperatures and monomer concentrations. For the CpZrCl₃ catalyst system activated by aluminoxane with a 40 mol % methyl group and a 60 mol % isobutyl group (MMAO_40/60), the polymerization temperature and monomer concentration significantly affected the molecular weight (M_n) of the obtained polymer and the catalytic activity. With an increase in the polymerization temperature from 0 to 27 °C, the catalytic activity and M_n increased, but these values dramatically decreased with the increasing polymerization temperature from 27 to 70 °C, meaning that the most suitable temperature was 27 °C. The CpZrCl₃/MMAO_40/60 ([Al]/[Zr] = 1000) catalyst system with the [NB] of 2.76 mol L^?1 at 27 °C showed the highest activity of 145 kg mol_Zr^?1 h^?1 and molecular weight of 211,000 g mol^?1. The polymerization using the CpZrCl₃/MMAO_40/60 catalyst system proceeds through the vinyl addition mechanism to produce atactic polynorbornene, which was soluble in chloroform, toluene, and 1,2‐dichlorobenzene, but insoluble in methanol. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1185–1191, 2008     

The synthesis and characterization of polyimide homopolymers based on 5(6)‐amino‐1‐(4‐aminophenyl)‐1,3,3‐trimethylindane

The isomeric diamine monomer 5(6)‐amino‐1‐(4‐aminophenyl)‐1,3,3‐trimethylindane (DAPI) was successfully synthesized via the dimerization of α‐methylstyrene followed by nitration and reduction. High molecular weight, soluble polyimides were synthesized via ester–acid solution imidization techniques and had glass‐transition temperature values ranging from 247 to 369 °C. The polymers were soluble in common organic solvents because of the asymmetric and nonplanar nature of DAPI and displayed good short‐term thermal stability by thermogravimetric analysis, as shown by their 5% weight‐loss values above 500 °C in air. The DAPI/(3,4‐dicarboxyphenyl) hexafluoropropane dianhydride (6FDA) polyimide also showed 2‐h thermal stability at 400 °C under nitrogen, despite the partial aliphatic character. Refractive index values as low as 1.571 were observed for DAPI/6FDA, which allows an estimated dielectric constant of 2.47 to be derived. The permeation of O₂ and N₂ was conducted on thin dense films. The bulky, bent, and isomeric nature of DAPI imparted film‐forming membranes that permitted high O₂ permeability. In combination with 3,3′,4,4′‐benzophenone tetracarboxylic dianhydride (BTDA), DAPI had a good combination of O₂ permeability and O₂/N₂ selectivity values of 2.8 Ba and 7.3, respectively. The polymerization method utilized to facilitate the cyclization of DAPI/BTDA to the polyimide affected the final thermal properties of the resulting polymer. The chemical imidization of DAPI/BTDA generated a polyimide with a glass‐transition temperature value of 311 °C and a 5% weight‐loss value in air of 457 °C. However, thermal and ester–acid imidization routes yielded an increase in the thermal properties. The ester–acid solution imidization of DAPI/BTDA produced a polymer glass‐transition temperature value of 333 °C and a 5% weight‐loss value of 525 °C in air. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2840–2854, 2000     

Thermal Degradation of Poly(Allyl Methacrylate) by Mass Spectroscopy and TGA

Allyl methacrylate, AMA was polymerized in CCl₄ solution by α,α′‐azoisobutyronitrile at 50°C. The thermal degradation mechanism of PAMA was characterized by MS, TGA‐FT‐IR and FT‐IR‐ATR methods. The mass spectrum and TGA thermogram showed two stage degradation. The first stage of degradation was mostly linkage type degradation for the fragmentation of pendant allyl groups at 225–350°C. In the second stage, at 395–515°C, the degradation is random scission and depolymerization types. This was also supported by direct thermal pyrolysis of polymer under vacuum. The degradation fragments of MS and TGA were in agreement. In the degradation process, monomer degraded further to CO, CO₂, allyl and ether groups. No strong monomer peak was observed in mass spectrum.     

Living/controlled radical polymerization of styrene with a new initiating system: DCDPS/FeCl3/PPh3

The living/controlled radical polymerization of styrene was investigated with a new initiating system, DCDPS/FeCl₃/PPh₃, in which diethyl 2,3‐dicyano‐2,3‐diphenylsuccinate (DCDPS) was a hexa‐substituted ethane thermal iniferter. The polymerization mechanism belonged to a reverse atom transfer radical polymerization (ATRP) process. The polymerization was controlled closely in bulk (at 100 °C) or in solution (at 110 °C) with a high molecular weight and quite narrow polydispersity (M_w/M_n = 1.18 ∼ 1.28). End‐group analysis results by ¹H NMR spectroscopy showed that the polymer was ω‐functionalized by a chlorine atom, which also was confirmed by the result of a chain‐extension reaction in the presence of a FeCl₂/PPh₃ or CuCl/bipy (2,2′‐bipyridine) catalyst via a conventional ATRP process. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 101–107, 2000     

MALDI‐TOF‐MS analysis of living cationic polymerization of vinyl ethers. II. Living nature of growing end and side reactions

Matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry analysis revealed that the HCl–vinyl ether adduct/SnCl₄/n‐Bu₄NCl initiating system induced living cationic polymerization of isobutyl vinyl ether in CH₂Cl₂ at ?78 °C, that is, the well‐resolved spectra demonstrated that the produced polymers consist of only one series of polymers carrying one initiator fragment at the α end and one methoxy group originated from quenching with methanol at the ω end. The polymer molecular weight as well as the terminal structure were unchanged even when the reaction mixtures were kept unquenched at ?78 °C for an interval of more than five times longer than the reaction period after complete consumption of monomer, which indicates the long lifetime of the living end even under such starved conditions. In contrast, the polymers obtained at a higher temperature, ?15 °C, showed an additional minor series of polymers formed via proton initiation, originating from adventitious water. Under the starved conditions, other side reactions occurred to generate minor series of polymers with an aldehyde ω end or a diisobutyl acetal ω end. Rather surprisingly, however, unsaturated C?C end groups were not detected, which means the absence of β‐proton elimination under these conditions. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1249–1257, 2001     

NOTE: Synthesis and Characterization of a Poly(acrylamide) with Pendant 1,4-piperazine-2,5-dione Moieties via Post-polymerization Cyclization

A poly(acrylamide) was synthesized from N ^α -Boc-N ^? -acrolyl-l-lysylglycine methyl ester via radical polymerization. This polymer typically had Mn ～ 100,000 g/mol, Mw ～ 300,000 g/mol, and a T_g of 93°C. Removal of Boc with TFA and cyclization with DABCO? in DMSO at 65°C afforded a soluble piperazinedione-containing polymer that had a T_g of 157°C and thermal stability up to 300°C. These results demonstrate a viable and efficient synthetic route to piperazinedione-containing polyacrylamides of high molecular weight. Related polymers that incorporate substituted indane moieties could be useful high T_g materials for fabrication of LC and NLO devices.     

Synthesis of poly(2‐furyloxirane) with high molecular weight and improved regioregularity using macrocyclic ether as a cocatalyst to potassium tert‐butoxide

2‐Furyloxirane (FO), a monomer usually obtained from a nonpetroleum route, was prepared from the epoxidation reaction of furfural and trimethylsulfonium chloride. About 200–300 g FO can be obtained in each preparation process. Although anionic polymerization of FO generally gives low‐ molecular‐weight polymers even after long periods of polymerization, the reaction was greatly improved when macrocyclic ether was used as a cocatalyst to potassium tert‐butoxide. When 18‐crown‐6 was used as a cocatalyst, poly(2‐furyloxirane) (PFO) with a number‐average molecular weight (M_n) of 41.5 kg/mol and a polydispersity index of 1.3 was obtained at 94% yield after polymerization at 40 °C for 72 h. The PFO obtained contained a 61.7% head‐to‐tail (H‐T) structure in the absence of the macrocyclic ether, and it reached 70.6% when cryptand[2,2,2] was used as a cocatalyst. PFO with higher regioregular structures showed improved thermal properties. For PFO with M_n of around 20.0 kg/mol, its glass transition temperature (T_g) increased from ?3 to 6 °C when the H‐T content was increased from 61.7 to 70.6%. Raising the M_n of PFO also raised T_g. For PFO with 68.9% H‐T structure, its T_g could reach 7 °C when M_n was increased to 40 kg/mol. This study shows two effective ways to improve the thermal and mechanical performances of the polymer. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis and polymerization of racemic and optically active β-substituted β-propiolactones. II: β-monosubstituted and β-disubstituted monomers and polymers with different optical purities

β-(trichloromethyl)-β-propiolactone (CCl₃-PL), β-(trifluoromethyl,methyl)-β-propiolactone (CF₃, Me-PL) and β-(trifluoromethyl,ethyl)-β-propiolactone (CF₃,Et-PL) have been obtained by the reaction of ketene with chloral, 1,1,1-trifluoroacetone and 1,1,1-trifluorobutanone, respectively. Chiral catalysis lead to optically active monomers. The enantiomeric excess of the lactones has been measured by ¹H-NMR spectroscopy, in the presence of 2,2,2-trifluoro-1-(9-anthryl)ethanol or an europium chiral shift reagent. Polymerizations have been carried out in bulk or in toluene, at 60°C or 80°C, using mainly organometallic initiators. The Polymers become insoluble and crystalline at enantiomeric excesses over 80% for CCl₃-PL and 70% for CF₃,Me-PL. Melting temperatures were recorded from 238 to 268°C for poly(CCl₃-PL) and from 78 to 100°C for poly(CF₃,Me-PL), depending upon the molecular weight and the enantiomeric excess. The ¹³C-NMR specroscopy of poly(CCL₃-PL) indicates that the polymerization of the corresponding lactone leads to polymers of increasing degrees of isotacticity with the enantiomeric excess of the monomer.     

Polymerization of 1,3‐dienes with functional groups. II. Free‐radical polymerization of N‐(2‐methylene‐3‐butenoyl)piperidine

The free‐radical homopolymerization and copolymerization behavior of N‐(2‐methylene‐3‐butenoyl)piperidine was investigated. When the monomer was heated in bulk at 60 °C for 25 h without an initiator, about 30% of the monomer was consumed by the thermal polymerization and the Diels–Alder reaction. No such side reaction was observed when the polymerization was carried out in a benzene solution with 1 mol % 2,2′‐azobisisobutylonitrile (AIBN) as an initiator. The polymerization rate equation was found to be R_p ∝ [AIBN]^0.507[M]^1.04, and the overall activation energy of polymerization was calculated to be 89.5 kJ/mol. The microstructure of the resulting polymer was exclusively a 1,4‐structure that included both 1,4‐E and 1,4‐Z configurations. The copolymerizations of this monomer with styrene and/or chloroprene as comonomers were carried out in benzene solutions at 60 °C with AIBN as an initiator. In the copolymerization with styrene, the monomer reactivity ratios were r₁ = 6.10 and r₂ = 0.03, and the Q and e values were calculated to be 10.8 and 0.45, respectively. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1545–1552, 2003     

Cationic ring‐opening polymerization of ϵ‐thionocaprolactone: Selective formation of polythioester

Cationic ring‐opening polymerization of ϵ‐thionocaprolactone was examined. The corresponding polythioester with the number‐average molecular weight (M_n ) of 57,000 was obtained in the polymerization with 1 mol % of BF₃ · OEt₂ as an initiator in CH₂Cl₂ at 28 °C for 5 h with quantitative monomer conversion. The M_n of the polymer increased with the solvent polarity and monomer‐to‐initiator ratio. No polymerization took place below −30 °C, and the monomer conversion and M_n of the polymer increased with the temperature in the range of −15 to 28 °C. The increase of initial monomer concentration was effective to improve the monomer conversion and the M_n of the obtained polymer. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4057–4061, 2000     

Polymerization of o‐quinodimethanes. V. Ionic polymerization of o‐quinodimethanes generated by thermal isomerization of corresponding benzocyclobutenes

The ionic polymerization of substituted o‐quinodimethanes via thermal isomerization of benzocyclobutenes is described. In the cationic polymerizations of 1‐methoxy‐o‐quinodimethane in the presence of various cationic initiators at 110 °C for 12 h, chain transfer reactions also considerably underwent besides the polymerization. Meanwhile, cationic polymerizations of 1‐trimethylsilyloxy‐o‐quinodimethane under the same conditions gave good yields of the corresponding polymer. Anionic polymerizations of 1‐cyano‐o‐quinodimethane in the presence of anionic initiators such as n‐BuLi or t‐BuOK were performed at various temperatures for 12 h. Good yields of hexane‐insoluble polymer, which was produced by anionic polymerization of corresponding o‐quinodimethane as an intermediate, were obtained above 120 °C. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 844–850, 2008     

Novel positive‐working and aqueous‐base‐developable photosensitive poly(imide benzoxazole) precursor

A novel positive‐working and aqueous‐base‐developable photosensitive poly(imide benzoxazole) precursor based on a poly(amic acid hydroxyamide) bearing phenolic hydroxyl groups and carboxylic acid groups, a diazonaphthoquinone (DNQ) photosensitive compound, and a solvent was developed. Poly(amic acid hydroxyamide) was prepared through the polymerization of 2,2‐bis(3‐amino‐4‐hydroxyphenyl)hexafluoropropane, trimellitic anhydride chloride, and 4,4′‐oxydibenzoyl chloride. Subsequently, the thermal cyclization of the poly(amic acid hydroxyamide) precursor at 350 °C produced the corresponding poly(imide benzoxazole). The inherent viscosity of the precursor polymer was 0.17 dL/g. The cyclized poly(imide benzoxazole) showed a high glass‐transition temperature of 372 °C and 5% weight loss temperatures of 535 °C in nitrogen and 509 °C in air. The structures of the precursor polymer and the fully cyclized polymer were characterized with Fourier transform infrared and ¹H NMR. The photosensitive polyimide precursor containing 25 wt % DNQ photoactive compound showed a sensitivity of 256 mJ/cm² and a contrast of 1.14 in a 3‐μm film with a 0.6 wt % tetramethylammonium hydroxide developer. A pattern with a resolution of 5 μm was obtained from this composition. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5990–5998, 2004     

Synthesis of polyphenylquinoxaline copolymers via aromatic nucleophilic substitution reactions of an A‐B quinoxaline monomer

A self‐polymerizable quinoxaline monomer (A‐B) has been synthesized and polymerized via aromatic nucleophilic substitution reactions. An isomeric mixture of self‐polymerizable quinoxaline monomers—2‐(4‐hydroxyphenyl)‐3‐phenyl‐6‐fluoroquinoxaline and 3‐(4‐hydroxyphenyl)‐2‐phenyl‐6‐fluoroquinoxaline—was polymerized in N‐methyl‐2‐pyrrolidinone (NMP) to afford high molecular weight polyphenylquinoxaline (PPQ) with intrinsic viscosities up to 1.91 dL/g and a glass‐transition temperature (T_g) of 251 °C. A series of comonomers was polymerized with A‐B to form PPQ/polysulfone (PS), PPQ/polyetherether ketone (PEEK), and PPQ/polyethersulfone (PES) copolymers. The copolymers readily obtained high intrinsic viscosities when fluorine was displaced in NMP under reflux. However, single‐electron transfer (SET) side reactions, which limit molecular weight, played a more dominant role when chlorine was displaced instead of fluorine. SET side reactions were minimized in the synthesis of PPQ/PS copolymers through mild polymerization conditions in NMP for longer polymerization times. Thus, the T_g's of PES (T_g = 220 °C), PEEK (T_g = 145 °C), and PS (T_g = 195 °C) were raised through the incorporation of quinoxaline units into the polymer. Copolymers with high intrinsic viscosities resulted in all cases, except in the case of PPQ/PEEK copolymers when 4,4′‐dichlorobenzophenone was the comonomer. © 2001 John Wiley & Sons, Inc. J Polym Sci A Part A: Polym Chem 39: 2037–2042, 2001