Copolymers of methyl methacrylate (MMA) and n-butyl acrylate (n-BA) were synthesized under atom transfer radical polymerization (ATRP) conditions. The molar infeed ratio was varied to obtain copolymers with different compositions. Methyl 2-bromo propionate was used as the initiator with CuBr/Cu(0)/N,N,NЈ,NЉ,NЉ-pentamethyldiethylenetriamine as the catalyst at 60°C. Molecular weight distribution was determined by gel permeation chromatography (GPC). Copolymer compositions (F M ) were calculated from 1 H NMR spectra. Reactivity ratios calculated with the Mao-Huglin terminal model at a high conversion were found to be r M ϭ 2.17 and r B ϭ 0.47. The polymerization mechanism was studied with the ␣-methyl region of MMA. The backbone methylene and carbonyl carbons of both MMA and n-BA units were found to be compositionally as well as configurationally sensitive. Complete spectral assignments were performed with the help of heteronuclear single quantum coherence (HSQC) spectroscopy along with total correlated spectroscopy (TOCSY). Further, the assignments of the carbonyl region were made with the help of heteronuclear multiple quantum coherence (HMBC) spectroscopy.
Atom transfer radical polymerization conditions were optimized and standardized with different initiator and catalyst systems. Acrylonitrile/n-butyl acrylate copolymers were synthesized with 2-bromopropionitrile as the initiator and CuCl/ Cu(0)/2,2 0 -bipyridine as the catalyst system. Variations of the feed composition led to copolymers with different compositions. The number-average molecular weight and the polydispersity index were determined by gel permeation chromatography. Quantitative 13 C{ 1 H} NMR was employed to determine the copolymer composition. The reactivity ratios calculated with a methodology based on the Mao-Huglin terminal model were r A ¼ 1.30 and r B ¼ 0.68 for acrylonitrile and n-butyl acrylate, respectively. The reactivity ratios determined by the modified Kelen-Tudos method were r A ¼ 1.29 6 0.01 and r B ¼ 0.67 6 0.01. 13 C{ 1 H} NMR and distortionless enhancement by polarization transfer (DEPT-45, 90, and 135) were used to distinguish methyl, methylene, methine, and quaternary carbon resonance signals. The overlapping and broad signals of the copolymers were assigned completely to various compositional and configurational sequences by the correlation of one-dimensional ( 1 H, 13 C{ 1 H}, and DEPT) and two-dimensional (heteronuclear single quantum coherence, total correlation spectroscopy, and heteronuclear multibond correlation) NMR spectral data. The complete spectral assignments of carbonyl and nitrile carbons were performed with the help of heteronuclear multibond correlation spectra. V V C 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: [2810][2811][2812][2813][2814][2815][2816][2817][2818][2819][2820][2821][2822][2823][2824][2825] 2005
Copolymers of acrylonitrile/methacrylic acid were prepared by photopolymerization using the uranyl ion as a photosensitizer. The comonomer reactivity ratios, determined by both Kelen-Tiidos (KT) and nonlinear error in variables (EVM) methods are = 0.135 ± 0.04 and = 3.618 ± 0.49. The microstructure was obtained in terms of the distribution of A-and M-centered triad sequences from 13C-{ } NMR spectra of the copolymers. Homonuclear 2D TOCSY NMR was used to simplify the complex spectra of A/M copolymers in terms of configurational/conformational sequences. The triad concentration calculated from Monte Carlo simulations (MC) gave good agreement with the triad concentration determined from NMR spectroscopy. MC simulation was also used to study the effect of the degree of polymerization on triad fractions.
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