Functional polyisobutylenes via electrophilic cleavage/alkylation

Lewis‐acid catalyzed degradation of poly(isobutylene‐co‐isoprene) (butyl rubber) in the presence of an alkoxybenzene compound was studied as a new route toward low molecular weight multifunctional polyisobutylenes. Simultaneous cleavage and functionalization of butyl rubber was conducted at ?70 °C and ?40 °C under TiCl₄ or AlCl₃ catalysis in 60/40 hexane/methylene chloride cosolvents in the presence of (3‐bromopropoxy)benzene (BPB) for various times up to 24 h. The butyl rubber (EXXON? Butyl 365) possessed M _n = 1.91 × 10⁵ g/mol, PDI = 1.66 (GPC/MALLS), and 2.30 mol % isoprene units (nearly exclusively trans ?1,4). At ?70 °C with TiCl₄, molecular weight was reduced to various values within the range 7 to 11 × 10³ g/mol depending on conditions; lower BPB concentration produced lower molecular weight. However, the ratio of isobutylene repeat units to BPB units (IB/Q ) remained constant at about 43:1, which is approximately the same as the ratio of isobutylene to isoprene repeat units (IB/IP) in the starting butyl rubber (42.5:1). At ?40 °C with TiCl₄, molecular weight was reduced to about 5 × 10³ g/mol, and IB/Q was reduced below IB/IP, indicating nearly a difunctional telechelic structure. AlCl₃ was a more active catalyst and produced results similar to TiCl₄ at ?40 °C, even when used at seven times lower concentration. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 1991–1997     

Optimization of direct arylation polymerization conditions for the synthesis of poly(3‐hexylthiophene)

Direct arylation polymerization (DArP) is an emerging alternative to Stille and Suzuki polymerizations. This method is attractive as it allows preparation of high‐molecular‐weight conjugated polymers in good yield without the need to metallate monomers. Despite this promise, for poly(3‐hexylthiophene) (P3HT) and related polymers that have β‐protons on the thiophene ring, DArP is known to produce β‐defects, which make the polymer properties different from polymers produced by traditional methods. Here, we demonstrate that DArP conditions based on simple, inexpensive, and bench‐stable reagents can be tuned to limit the amount of defects and produce P3HT with properties remarkably similar to Stille P3HT. Specifically, lowering the reaction temperature, lowering the amount of catalyst, and using a bulkier carboxylate ligand is critical. Optimized conditions include reacting 2‐bromo‐3‐hexylthiophene with 0.25 mol % of Pd(OAc)₂, 1.5 equivalents of K₂CO₃, and 0.3 equivalents of neodecanoic acid in N,N‐dimethylacetamide at 70 °C and give DArP P3HT with ～60% yield, regioregularity of 93.5%, molecular weight of 20 kDa, polydispersity of 2.8, and melting point of 217 °C, providing a very close match to Stille P3HT, which is obtained with 70–80% yield, 91–94% regioregularity, molecular weight of 15–25 kDa, polydispersity of 2.5–2.8, and melting point of 214–221 °C. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2660–2668     

Demonstration of isospecific free radical polymerization of acrylate controlled by conformation and chirality of monomer

Radical polymerization of lactic acid‐based chiral and achiral methylene dioxolanones, a model for conformationally s‐cis locked acrylate, was carried out with AIBN to demonstrate an isospecific free radical polymerization controlled by chirality and conformation of monomer. Polymerization of the dioxolanones proceeded smoothly without ring opening to give a polymer with moderate molecular weight and 100% of maximum isotacticity. ESR spectrum indicated a twisted conformation of the growing poly(methylene dioxolanone) radical in contrast to an acyclic analogous radical, suggesting a restriction of the free rotation around main chain C_α? C_β bond of the growing radical center. Chirality as well as the polarity and bulkiness of monomer affected the polymer tacticity, and chiral alkyl substituent would afford a high isotactic polymer, in which higher the enantiomeric excess of the monomer was, higher the isotacticity of the polymer was. While, achiral or polar substituents including dibenzyl and trichloromethyl groups would afford an atactic polymer. In addition, glass transition temperature (T_g) of the resulting polymers was significantly high, ranging from 172.2 to 229.8 °C, and even for an isotactic polymer T_g was as high as 206.8 °C. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2007–2016     

Novel aromatic polymers from benzaldehyde and triphenylamine derivatives: Synthesis,electrochromic, and photochemical properties

A series of novel triphenylamine‐based polymers were synthesized from benzaldehyde and triphenylamine derivatives. All the polymers having high molecular weight are readily soluble in many organic solvents and could be solution‐cast into amorphous films. They had glass transition temperatures (T_gs) in the range of 193–217 °C, and 10% weight loss temperatures in excess of 475 °C. Cyclic voltammograms of all polymers showed reversible oxidation redox peaks and E_onset around 0.42–0.90 V, indicating that the polymers are electrochemically active and stable. In addition, all these polymers revealed photochemical characteristics in conformity with their electrochromic characteristics. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2118–2131, 2009     

Stereoregular P(MMA)‐clay nanocomposites by metallocene catalysts: In situ synthesis and stereocomplex formation

This contribution reports the synthesis and characterization of stereochemically controlled, as well as crystalline stereocomplex, P(MMA)‐clay nanocomposites using metallocene complexes and alane‐intercalated clay activators. The ligand elimination and exchange reactions involving Lewis acids E(C₆F₅)₃ (E = Al, B) and an organically modified montmorillonite clay were employed to synthesize the alane‐intercalated clay activators. When combined with dimethyl metallocenes of various symmetries, these clay activators brought about efficient MMA polymerizations leading to in situ polymerized, stereochemically controlled P(MMA)‐intercalated clay nanocomposites. The most noticeable thermal property enhancement observed for the clay nanocomposite P(MMA), when compared with the pristine P(MMA) having similar molecular weight and stereomicrostructure, has a considerable increase in T_g (≥10 °C). Mixing of dilute THF solutions of two diastereomeric nanocomposites in a 1:2 isotactic to syndiotactic ratio, followed by reprecipitation or crystallization procedures, yielded unique double‐stranded helical stereocomplex P(MMA)‐clay nanocomposites with a predominantly exfoliated clay morphology. Remarkably, the resulting crystalline stereocomplex P(MMA) matrix is resistant to the boiling‐THF extraction and its clay nanocomposites exhibit high T_m of 201 to 210 °C. Furthermore, the stereocomplex P(MMA)‐clay nanocomposite shows a one‐step, narrow decomposition temperature window and a single, high maximum rate decomposition temperature of 377 °C. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2581–2592, 2007     

The physical and NMR characterizations of allyl‐ and crotylcelluloses

Tri‐O‐allylcellulose (degree of polymerization, DP ∼112) was prepared in ∼91% yield, and tri‐O‐crotylcellulose (DP ∼138) was prepared in ∼56% yield from microcrystalline cellulose (DP ∼172, and polydispersity index, PDI ∼1.95) using modified literature methods. Number‐average molecular weight (M_n = 31,600), weight‐average molecular weight (M_w = 191,800), and PDI = 6.07 data suggested that tri‐O‐allylcellulose may be crosslinking in air to generate branched chains. The polymer was stabilized with 100 ppm butylated hydroxy toluene (BHT). The material without BHT experienced glass transition (T_g, differential‐scanning calorimetry, DSC) between −2 and +3 °C, crosslinked beyond 100 °C, and degraded at 298.6 °C (by thermogravimetric analysis, TGA). M_n (45,100), M_w (118,200), PDI (2.62), and thermal data (T_g − 5 to +3 °C, melting point 185.8 °C, recrystallization 168.9 °C, and degradation 343.6 °C) on tri‐O‐crotylcellulose suggested that the polymer was formed with about the same polydispersity as the starting material and is heat stable. While allylcellulose generated continuous flexible yellow films by solution casting, crotylcellulose precipitated from solution as brittle white flakes. Dynamic mechanical analysis (DMA) data on allylcellulose films (T_g − 29.1 °C, Young's modulus 5.81 × 10⁸ Pa) suggest that the material is tough and flexible at room temperature. All ¹H and ¹³C resonances in the NMR spectra were identified and assigned using the following methods: Double‐quantum filter correlation spectroscopy (DQF COSY) was used to assign the network of seven protons in the anhydroglucose portion of the repeat unit. The proton assignments were verified and confirmed by total correlation spectroscopy (TOCSY). A combination of heteronuclear single‐quantum coherence (HSQC) and ¹³C spectroscopies were used to identify all bonded carbon–hydrogen pairs in the anhydroglucose portion of the repeat unit, and assign the carbon nuclei chemical shift values. Heteronuclear multiple bond correlation (HMBC) spectroscopy was used to connect the resonances of methines and methylenes at positions 2, 3, and 6 to the methylene resonances of the allyl ethers. TOCSY was used again to identify the fifteen ¹H resonances in the three pendant allyl groups. Finally, a combination of HSQC, HMBC, and ¹³C spectroscopies were used to identify each carbon in the allyl pendants at 2, 3, and 6. Because of line broadening and signal overlap, we were unable to identify the conformational arrangement about the C5 and C6 bond in tri‐O‐allyl‐ and tri‐O‐crotylcelluloses. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1889–1902, 2000     

Effect of molecular weight on conformational characteristics of poly(3‐hexyl thiophene)

This research focused on the effect of molecular weight and investigated the conformational characteristics of poly(3‐hexyl thiophene) (P3HT). An integrated system consisting of a gel permeation chromatograph, a static light scattering unit, and a viscometer was used for the study. It also estimated the radius of gyration (R_g) values of unsubstituted poly(thiophene) (PT) chains computationally using rotational‐isomeric‐states modeling and compared them with the experimental data for P3HT. In the low molecular weight region (20,000 to 30,000), both chains had nearly the same R_g values, meaning that the effect of side‐chains is limited. At higher molecular weights, the P3HT chains expanded more than the PT chains. In the molecular weight region from 20,000 to 60,000, both characteristic ratio and persistence length showed considerable molecular weight dependence. Beyond a molecular weight of 60,000, the molecular weight dependence decreased, and these parameters approached constant values, 16 and 3 nm, respectively. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 1273–1277     

Linear polyurethanes made from naturally occurring tartaric acid

Naturally occurring tartaric acid was used as raw material for the synthesis of novel linear polyurethanes (PURs) bearing two carboxylate side‐groups in the repeating unit. Aliphatic and aromatic PURs were obtained by reaction in solution of alkyl and benzyl tartrates with hexamethylene diisocyanate and 4,4′‐methylene‐bis(phenyl isocyanate), respectively. All the novel PURs were thermally stable and optically active. The aliphatic carboxylate‐containing PURs had M_w in the 40–70 kDa range, with PD between 2.1 and 2.5; all were semicrystalline polymers with melting temperatures between 100 and 150 °C and T_g in the 50–80 °C range. The aromatic PURs were amorphous materials with molecular weights between 18 kDa and 25 kDa and T_g above 130 °C. Hydrogenolysis of the PUR made from hexamethylene diisocyanate and benzyl tartrate yielded PURs containing up to 40% of free carboxylic side‐groups. The tartrate‐derived PURs displayed enhanced sensitivity to hydrolysis compared with their unsubstituted 2,6‐PUR homologs. The PURs bearing free carboxylic groups were unique in being degraded by water upon incubation under physiological conditions. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2391–2407, 2009     

Multiple melting behavior of poly(butylene succinate). I. Thermal analysis of melt‐crystallized samples

The multiple melting behavior of poly(butylene succinate) (PBSu) was studied with differential scanning calorimetry (DSC). Three different PBSu resins, with molecular weights of 1.1 × 10⁵, 1.8 × 10⁵, and 2.5 × 10⁵, were cooled from the melt (150 °C) at various cooling rates (CRs) ranging from 0.2 to 50 K min^?1. The peak crystallization temperature (T_c) of the DSC curve in the cooling process decreased almost linearly with the logarithm of the CR. DSC melting curves for the melt‐crystallized samples were obtained at 10 K min^?1. Double endothermic peaks, a high‐temperature peak H and a low‐temperature peak L, and an exothermic peak located between them appeared. Peak L decreased with increasing CR, whereas peak H increased. An endothermic shoulder peak appeared at the lower temperature of peak H. The CR dependence of the peak melting temperatures [T_m(L) and T_m(H)], recrystallization temperature (T_re), and heat of fusion (ΔH) was obtained. Their fitting curves were obtained as functions of log(CR). T_m(L), T_re, and ΔH decreased almost linearly with log(CR), whereas T_m(H) was almost constant. Peak H decreased with the molecular weight, whereas peak L increased. It was suggested that the rate of the recrystallization decreased with the molecular weight. T_m(L), T_m(H), T_re, and T_c for the lowest molecular weight sample were lower than those for the others. In contrast, ΔH for the highest molecular weight sample was lower than that for the others. If the molecular weight dependence of the melting temperature for PBSu is similar to that for polyethylene, the results for the molecular weight dependence of PBSu can be explained. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2411–2420, 2002     

Facile synthesis for well‐defined A2B miktoarm star copolymer of poly(3‐hexylthiophene) and poly(methyl methacrylate) by the combination of anionic polymerization and click reaction

We have introduced a facile synthetic route for well‐defined A₂B miktoarm star copolymer composed of regioregular poly(3‐hexylthiophene) and poly(methyl methacrylate) ((P3HT)₂PMMA) by the combination of anionic polymerization and click reaction. First, we synthesized PMMA terminated with 1,3,5‐tris(bromomethyl)benzene (PMMA‐(Br)₂) by anionic polymerization, and two bromines attached to the end of the PMMA chains were replaced by azides (PMMA‐(N₃)₂). Also, monoethynyl‐capped P3HT was synthesized by Grignard metathesis polymerization and post‐end functionalization. Then, copper(I)‐catalyzed Huisgen 1,3‐dipolar cycloaddition click reaction between monoethynyl‐capped P3HT and PMMA‐(N₃)₂ was performed to synthesize (P3HT)₂PMMA. We used a slightly excess amount of monoethynyl‐capped P3HT so that all of the azide groups at the end of the PMMA chains completely reacted with monoethynyl‐capped P3HT. After complete removal of unreacted monoethynyl‐capped P3HT by column chromatography, pure (P3HT)₂PMMA with narrow molecular weight distribution (the polydispersity of 1.18) was obtained. The weight fraction of P3HT and the total molecular weight of (P3HT)₂PMMA are 0.48 and 16,000, respectively. To investigate the effect of the chain architecture on optical property and thin‐film morphology, we synthesized two linear P3HT‐b‐PMMAs (P3HT‐b‐PMMA‐L and P3HT‐b‐PMMA‐H) with similar weight fraction of P3HT block (0.48 for P3HT‐b‐PMMA‐L and 0.45 for P3HT‐b‐PMMA‐H) but two different total molecular weights (7900 for P3HT‐b‐PMMA‐L and 15,300 for P3HT‐b‐PMMA‐H). UV–visible (UV–vis) absorption spectrum and the fibril width of (P3HT)2PMMA thin film were similar to those of P3HT‐b‐PMMA‐L thin film. However, UV–vis spectrum for P3HT‐b‐PMMA‐H thin film was red‐shifted and the fibril width of P3HT‐b‐PMMA‐H was much larger than that of (P3HT)₂PMMA. This indicates that the π–π interaction between P3HT arms in (P3HT)₂PMMA is strong enough to arrange two P3HT backbone chains in (P3HT)₂PMMA to stack one by one along the nanofibril axis. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Synthesis and characterization of phthalazinone containing poly(arylene ether)s via a novel N–C coupling reaction

High‐molecular‐weight poly(phthalazinone)s with very high glass‐transition temperatures (T_g's) were synthesized via a novel N–C coupling reaction. New bisphthalazinone monomers ( 7a–e ) were synthesized from 2‐(4‐chlorobenzoyl) phthalic acid in two steps. Poly(phthalazinone)s, having inherent viscosities in the range of 0.34–0.91 dL/g, were prepared by the reaction of the bis(phthalazinone) monomers with an activated aryl halide in a dipolar aprotic solvent in the presence of potassium carbonate. The poly(phthalazinone)s exhibited T_g's greater than 230 °C. polymer 8b synthesized from diphenyl biphenol and bis(4‐flurophenyl) sulfone demonstrated the highest T_g of 297 °C. Thermal stabilities of the poly(phthalazinone)s were determined by thermogravimetric analysis. All the poly(phthalazinone)s showed a similar pattern of decomposition with no weight loss below 450 °C in nitrogen. The temperatures of 5% weight loss were observed to be about 500 °C. The poly(phthalazinone)s containing 4,4′‐isopropylidenediphenol and 4,4′‐(hexafluoroisopropylidene) diphenol and diphenyl ether linkage were soluble in chlorinated solvents such as chloroform. Other poly‐(phthalazinone)s were soluble in dipolar aprotic solvents such as N,N′‐dimethylacetamide. The soluble poly(phthalazinone)s can be cast as flexible films from solution. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2481–2490, 2003     

Synthesis and characterization of a novel electrochromic aromatic polyamide from AB‐type triphenylamine‐based monomer

A new triphenylamine‐based polyamide I was prepared by direct polycondensation of AB‐type monomer, 4‐amino‐4′‐carboxy‐4″‐methoxytriphenylamine ( 4 ), in the presence of triphenyl phosphite and pyridine as condensation agents. The obtained polyamide I showed excellent solubility in aprotic polar solvents such as NMP, DMAc, DMF, and DMSO and could be cast into transparent film with weight‐average molecular weight (M_w = 63,400) and polydispersity index (PDI = 1.79). The polyamide I exhibited good thermal stability with relatively high glass‐transition temperature (282 °C), 10% weight‐loss temperature above 470 °C under a nitrogen atmosphere, and char yield at 800 °C in nitrogen higher than 64%. It also showed maximum ultraviolet‐visible absorption at 362 nm and exhibited fluorescence emission maxima at 493 nm in NMP solution with fluorescence quantum yield 4.4%. Cyclic voltammogram of polyamide I film cast onto an indium tin oxide coated glass substrate exhibited one oxidative redox couple at 0.72 V (oxidation onset potential) versus Ag/AgCl in acetonitrile solution and revealed good stability of the electrochromic characteristic with a color change from colorless to green at applied potentials ranging from 0.00 to 1.10 V. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1988–2001, 2009     

Exhaustive and partial alkoxylation of polymethylhydrosiloxane by copper‐catalyzed dehydrocoupling with alcohols: Synthesis,crosslinking behavior,and thermal properties of the products

Polymethylhydrosiloxane (PMHS) reacts with aliphatic and aromatic alcohols at room temperature in the presence of [CuH(PPh₃)]₆ complex catalyst to give poly[(methyl) (alkoxy)siloxane]s in high yields. Reactivity of alcohols decreases in the order of p‐methoxyphenol > p‐cresol > phenol > benzyl alcohol > allyl alcohol > ethanol > isopropanol > tert‐butyl alcohol. Partially p‐cresylated polymers, which still retain unreacted Si? H bonds, react further with ethylene glycol or water to form cross‐linked polymers, which, depending on the extent of cross linking, gelate during the cross‐linking process. Propargyl alcohol reacts with PMHS very rapidly to give exhaustively and partially propargyloxylated PMHS. Resulting polymers, upon heating, undergo crosslinking. Partially propargyloxylated polymers display high thermal stability [T_d5 (temperature of 5% weight loss) > 500 °C] as compared with starting PMHS (243 °C) and exhaustively propargyloxylated one (414 °C). © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Poly(3‐hexylthiophene)‐b‐poly(3‐cyclohexylthiophene): Synthesis,microphase separation,thin film transistors,and photovoltaic applications

We report the synthesis, characterization, microphase separation, field‐effect charge transport, and photovoltaic properties of regioregular poly(3‐hexylthiophene)‐b‐poly(3‐cyclohexylthiophene) (P3HT‐b‐P3cHT). Two compositions of P3HT‐b‐P3cHT (HcH63 and HcH77) were synthesized with weight‐average molecular weights of 155,500 and 210,800 and polydispersity indices of 1.45 and 1.57, respectively. Solvent‐casted HcH77 was found to self‐assemble into nanowires with a width of 12.5 ± 0.9 nm and aspect ratios of 50–120, as observed by TEM imaging. HcH77 and HcH63 annealed 280 °C were observed by small angle X‐ray scattering (SAXS) and wide angle X‐ray scattering (WAXS) to be microphase‐separated with characteristic length scales of 17.0–21.7 nm. The microphase‐separated domains were shown to be crystalline with interlayer backbone (100) d‐spacings of 1.69 and 1.40 nm, which correspond to the P3HT and P3cHT blocks, respectively. Field‐effect transistors fabricated from P3HT‐b‐P3cHT thin films showed a mobility of holes (0.0019 cm²/Vs) which is independent of thermal annealing. Bulk heterojunction solar cells based on HcH77/fullerene (PC₇₁BM) blend thin films had a maximum power conversion efficiency of 2.45% under 100 mW/cm² AM1.5 solar illumination in air. These results demonstrate that all‐conjugated block copolymers are suitable semiconductors for applications in field‐effect transistors and bulk heterojunction solar cells. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 614–626, 2010     

Poly(phenyl methacrylate) and poly(1‐naphthyl methacrylate) prepared in microemulsions

Phenyl methacrylate and 1‐naphthyl methacrylate were polymerized in microemulsions using stearyltrimethylammonium chloride, cetyltrimethylammonium bromide, and a mixture of nonionic Triton surfactants to form latexes that were 20–30 nm in diameter. A temperature of 70 °C was needed to obtain polymers using thermal initiation. The tacticities of poly(phenyl methacrylate) (PPhMA) (55% rr) and poly(1‐naphthyl methacrylate) (P‐1‐NM) (47% rr) were the same as those of the polymers prepared in toluene solutions. The weight average molecular weights were 1 × 10⁶ and 5 × 10⁵ g/mol for PPhMA and P‐1‐NM prepared in microemulsions with very broad distributions. PPhMA samples from microemulsions and solution had the same T_g = 127 °C. P‐1‐NM from microemulsions had T_g = 145–147 °C compared with T_g = 142 °C for P‐1‐NM from solution. The molecular weights and the glass‐transition temperatures of both PPhMA and P‐1‐NM from microemulsions are substantially higher than any previously reported. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 519–524, 2001     

Preparation of high molecular weight polybenzoxazine prepolymers containing siloxane unites and properties of their thermosets

High‐molecular‐weight polybenzoxazine prepolymers containing polydimethylsiloane unit in the main‐chain have been synthesized from α,ω‐bis(aminopropyl)polydimethylsiloxane (PDMS) (molecular weight = 248, 850, and 1622) and bisphenol‐A with formaldehyde. Moreover, another type of prepolymers was prepared using methylenedianiline (MDA) as codiamine with PDMS. The weight average molecular weight of the obtained prepolymers was estimated from size exclusion chromatography to be in the range of 8000–11,000. The chemical structures of the prepolymers were investigated by ¹H NMR and IR analyses. The prepolymers gave transparent free standing films by casting their dioxane solution. The prepolymer films after thermally cured up to 240 °C gave brown colored transparent and flexible polybenzoxazine films. Tensile test of the films revealed that the elongation at break increased with increasing the molecular weight of PDMS unit. Dynamic mechanical analysis of the thermosets showed that the T_gs were as high as 238–270 °C. The thermosets also revealed high thermal stability as evidenced by the 5% weight loss temperatures in the range of 324–384 °C from thermogravimetic analysis. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Temperature dependence of the activation volume in a nonlinear optical polymer: Evidence for chromophore reorientation induced by sub-Tg relaxations

Second harmonic generation (SHG) was used to measure the temperature dependence of the reorientation activation volume of 4-(diethylamino)-4′-nitrotolane (DEANT) in poly(methyl methacrylate) (PMMA). The decay of the SHG signal from films of DEANT/PMMA was recorded at hydrostatic pressures up to 3060 atm and at different temperatures between 25°C below the glass transition temperature to 35°C above it. The activation volume, ΔV*_αβ associated with the long range α-type motion of the polymer remained constant at 213 ± 10 ų between T_g − 25°C and T_g + 10°C. At higher temperatures, ΔV*_αβ decreased linearly with increasing temperature. The activation volume, ΔV*_αβ, associated with short range secondary relaxations was constant over the entire temperature range with a value of 77 ± 10 ų. The data suggest that above T_g chromophore reorientation is coupled to both the long range and local motions of the polymer; whereas, well below T_g chromophore reorientation is closely coupled to the local relaxations of the polymer. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 901–911, 1998     

Poly(triphenylamine)s derived from oxidative coupling reaction: Substituent effects on the polymerization,electrochemical, and electro‐optical properties

A series of triphenylamine‐based polymers containing electron‐donating methoxy (? OCH₃) and electron‐withdrawing cyano or nitro (? CN or ? NO₂) substituents in the main chains have been designed and investigated. These conjugated polymers ( P1 – P3 ) could be readily prepared by oxidative coupling polymerization from monomers ( M1 – M3 ) using FeCl₃ as an oxidant. The P2 and P3 exhibited moderate high T_g values (203–205 °C) and thermal stability. These polymers in NMP solution showed UV–vis absorption around 288–404 nm and photoluminescence peaks around 435–492 nm. P1 – P3 showed reversible oxidation redox couples at E_onset = 0.67, 0.99, and 1.00 V in solution of 0.1 M tetrabutylammonium perchlorate (TBAP)/acetonitrile (CH₃CN), respectively. M3 and P3 exhibited reversible reduction redox couples at E_onset = ?1.04 and ?1.03 V. These polymers also revealed electrochromic characteristic changing color at different potential. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 285–294, 2009     

Novel thermally stable triarylamine‐containing aromatic polyamides bearing anthrylamine chromophores for highly efficient green‐light‐emitting materials

A series of novel polyamides with pendent anthrylamine units were prepared via the direct phosphorylation polycondensation from various diamines and the anthrylamine‐based aromatic dicarboxylic acid, 9‐[N,N‐di(4‐carboxyphenyl)amino]anthracene (4). The aromatic polyamides had useful levels of thermal stability associated with relatively high softening temperatures (T_s) (290–300 °C), 10% weight‐loss temperatures (T_d¹⁰) nearly in excess of 550 °C, and char yields at 800 °C in nitrogen higher than 60%. These aromatic polyamides I exhibited highly photoluminescence quantum yield in NMP solution ranges from 55% for Ia to 74% for Ie due to the introduction of anthrylamine chromophores. Cyclic voltammograms of the polyamide films cast onto an indium‐tin oxide (ITO)‐coated glass substrate exhibited one oxidation and reduction couples (E_onset) around 1.10 and ?1.50 V versus Ag/AgCl in acetonitrile (CH₃CN) and DMF solutions, respectively. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7354–7368, 2008     

Synthesis of multiarmed poly(3‐hexyl thiophene) star polymer with microgel core by GRIM and ATRP methods

Regioregular poly(3‐hexyl thiophene) (rr‐P3HT)‐based star polymers were synthesized by a crosslinking reaction of the linear rr‐P3HT macroinitiator and ethylene glycol dimethacrylate (EGDMA) crosslinker through Ru‐based atom transfer radical polymerization (ATRP), where the rr‐P3HT macroinitiator was prepared by Grignard metathesis method (GRIM) followed by end functionalization of the ATRP initiator with chlorophenylacetate (CPA) to the rr‐P3HT. Relatively high molecular weight of the star polymers were obtained (M_p = 8,988,000 g/mol), which consisted of large numbers of the rr‐P3HT arm chains radiating from the EGDMA‐based microgel core. The yield of the star polymers were strongly affected by the added amount of the EGDMA crosslinker. The crystalline structure of the rr‐P3HT by intermolecular π‐π stacking interaction gradually decreased as the star polymer formed, which was confirmed by differential scanning calorimeter (DSC), atomic force microscopy (AFM), and electro‐optical analyses. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011