The synthesis of high molecular weight star-shaped polymers comprising poly(1,3-cyclohexadiene) arms coupled to a divinylbenzene (DVB) core is reported. In-situ FTIR spectroscopy was used to verify first-order polymerization kinetics for 1,3-cyclohexadiene at 40 °C in cyclohexane with a 10 wt % monomer concentration using a tetramethylethylenediamine (TMEDA) to n-butyllithium (n-BuLi) ratio of 5/4. The propagation rate constant was determined to be 0.31 L mol-1 s-1. The degree of 1,2-addition (70%) vs 1,4-addition (30%) for 1,3-cyclohexadiene was determined using 1H NMR spectroscopy. The molecular weights of the preformed arms were 10 000 and 5000 g/mol, and the ratio of DVB to n-BuLi was systematically varied from 6:1 to 24:1. Gel permeation chromatography coupled with light scattering detection was utilized to detect the formation of star-shaped polymers and the presence of star−star coupling. In-situ spectroscopy and obvious color changes indicated that the addition of DVB to poly(1,3-cyclohexadienyllithium) was rapid. The molecular weight distribution (M w/M n) of the star polymers ranged from 1.4 to 1.9. The polymeric materials were thermally stable to 330 °C under a nitrogen environment. The refractive indices of both the homopolymers and star polymers were 1.572 at 600 nm and remained relatively constant from 1600 to 550 nm. The T g of the high molecular weight star-shaped polymers was 150 °C.

High molecular weight poly(2,5‐benzophenone) derivatives were prepared by Ni(0)‐catalyzed coupling of 4′‐substituted 2,5‐dichlorobenzophenones. Monomers were synthesized by the Friedel–Crafts reaction of 2,5‐dichlorobenzoyl chloride and alkyl‐substituted benzenes in the presence of aluminum chloride. The resulting polymers are soluble and show no evidence of crystallinity by DSC. Number average molecular weights are in the range of 9.2 × 103–11.7 × 103 g/mol by multiple angle laser light scattering (MALLS). Molecular weights obtained by MALLS are only slightly lower (∼90%) than those obtained by GPC (polystyrene standards). These polymers exhibit high thermal stability with glass transition temperatures ranging from 173 to 225°C and weight loss occurring above 450°C in nitrogen and 430°C in air. Additionally, the polymers were blended and the resulting polymer films appear to be miscible by DSC results. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2611–2618, 1998

We present neutron spin echo and structural measurements on a perdeuterated miscible polymer blend: poly(ethylene oxide)[PEO]/poly(methyl methacrylate)[PMMA], characterized by a large difference in component glass transition temperatures and minimal interactions. The measurements cover the q range 0.35 to 1.66 A(-1) and the temperature range Tg -75 to Tg +89 K, where Tg is the blend glass transition. The spectra, obtained directly in the time domain, are very broad with stretching parameters beta approximately 0.30. The relaxation times vary considerably over the spatial range considered however at none of the q values do we see two distinct relaxation times. At small spatial scales relaxations are still detectable at temperatures far below Tg. The temperature dependence of these relaxation times strongly resembles the beta-relaxation process observed in pure PMMA.

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Nonlinear monomer reactivity ratios for the homogeneous free‐radical copolymerization of acrylonitrile and methyl acrylate were determined from 1H NMR and real‐time Fourier transform infrared (FTIR) analyses. All 1H NMR data were obtained on polymers isolated at low conversions (<10%), whereas the FTIR data were collected in situ. The copolymerizations were conducted in N,N‐dimethylformamide at 62 °C and were initiated with azobisisobutyronitrile. The real‐time FTIR technique allowed for many data points to be collected for each feed composition, which enabled the calculation of copolymer compositions (dM1/dM2) with better accuracy. Monomer reactivity ratios were estimated with the Mayo–Lewis method and then were refined via a nonlinear least‐squares analysis first suggested by Mortimer and Tidwell. Thus, monomer reactivity ratios at the 95% confidence level were determined to be 1.29 ± 0.2 and 0.96 ± 0.2 for acrylonitrile and methyl acrylate, respectively, which were valid under the specific system conditions (i.e., solvent and temperature) studied. The results are useful for the development of acrylonitrile (<90%) and methyl acrylate, melt‐processable copolymer fibers and films, including precursors for carbon fibers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2994–3001, 2004

High molecular weight star‐shaped polystyrenes were prepared via the coupling of 2,2,6,6‐tetramethyl‐1‐piperidinyloxy (TEMPO) terminated polystyrene oligomers with divinylbenzene (DVB) in m‐xylene at 138 °C. The optimum ratio of the coupling solvent (m‐xylene) to divinylbenzene was determined to be 9 to 1 based on volume. Linear polystyrene oligomers (Mn = 19,300 g/mol, Mw/Mn = 1.10) were prepared in bulk styrene using benzoyl peroxide in the presence of TEMPO at approximately 130 °C under an inert atmosphere. Coupling of the TEMPO‐terminated oligomers under optimum conditions resulted in a product with a number average molecular weight exceeding 300,000 g/mol (Mw/Mn = 3.03) after 24 h, suggesting the formation of relatively well‐defined star‐shaped polymers. Additionally, the intrinsic viscosities of the star‐shaped products were lower than calculated values for linear analogs of equivalent molecular weight, which further supported the formation of a star‐shaped architecture. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 216–223, 2001

High molecular weight star-shaped polystyrenes were prepared via the coupling of 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) terminated polystyrene oligomers with divinylbenzene (DVB) in m-xylene at 138°C. The optimum ratio of the coupling solvent (m-xylene) to divinylbenzene was determined to be 9 to 1 based on volume. Linear polystyrene oligomers (M n ϭ 19,300 g/mol, M w /M n ϭ 1.10) were prepared in bulk styrene using benzoyl peroxide in the presence of TEMPO at approximately 130°C under an inert atmosphere. Coupling of the TEMPO-terminated oligomers under optimum conditions resulted in a product with a number average molecular weight exceeding 300,000 g/mol (M w /M n ϭ 3.03) after 24 h, suggesting the formation of relatively well-defined star-shaped polymers. Additionally, the intrinsic viscosities of the star-shaped products were lower than calculated values for linear analogs of equivalent molecular weight, which further supported the formation of a star-shaped architecture.

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