Atom transfer radical bulk copolymerization of MA and MMA was performed in the presence of CuCl/PMDETA as catalyst system and trichloromethyl-terminated poly(vinyl acetate) macroinitiator at 808C. The overall monomer conversion was followed gravimetrically and chemical composition of the copolymer was determined by 1 H-NMR spectrometry. The results have been used to calculate monomer reactivity ratios by linear and nonlinear methods. Reactivity ratios calculated were in the range of 0.3766 -0.4988 and 1.8832 -2.0963 for MA and MMA, respectively. These values were in good agreement with the values reported for a similar system in the free radical copolymerization. It was observed that the copolymerization system tends to produce a random copolymer with longer sequences of MMA than MA in the initial stage of polymerization before any significant decrease of the concentration of MMA in the monomer mixture. Copolymer microstructures in this study indicated that radical stabilization capability of MMA compared to MA is higher. The accuracy of the reactivity ratios were confirmed by 95% joint confidence limits. It was found that considering the effect of conversion in these methods makes the calculation result more accurate. The theoretical composition drifts in the comonomer mixture and copolymer as a function of the overall monomer conversion are also reported.
Structural analysis of the poly(vinyl acetate)-block-poly(methyl acrylate-co-methyl methacrylate) with different MA/MMA ratios was characterized by 1D and 2D NMR. The effect of the sequence distribution, composition and stereoregularity on the unknown signals of α-CH 3 , backbone methylene and methin carbons were analyzed by 1D ( 13 C/DEPT-135) and 2D HSQC NMR. Furthermore, the theoretical values of triad, dyad and triad fractions of these carbons confirmed the spectral assignments. The sensitivity of the vicinal and geminal couplings of methin and methylene protons to the sequence distribution and composition were characterized using the 2D TOCSY NMR method. The influence of the sequence distribution on the theoretical glass transition temperatures of the MA/MMA copolymers was also examined using the Johnston (extended Fox) equation and experimental T g .
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.