Preparation of PMMA-co-PMPS copolymers via catalytic chain transfer polymerization techniqueand evaluation of their apparent chain transfer constants

Catalytic chain transfer polymerization (CCTP) of methyl methacrylate (MMA) and 7-methacryloxypropyltrimethoxysilane (MPS) was performed using toluene as the solvent at 601 in the present of bis (boron difluorodimethylglyoximate) cobaltate (?) (CoBF) as catalytic chain transfer agent and AIBN as the initiator. Vinyl-terminated copolymers with low molecular weight were successfully prepared by CCTP in this case. H-NMR was employed to prove the presence of vinyl unsaturated end groups of the as-prepared polymer. The effect of structure on thermal behavior was investigated by using thermogravimetry (TG) in nitrogen atmosphere. In contrast to PMMA-co-PMPS prepared in absence of CoBF, the differential thermogravi metry (DTG) curves of the copolymer synthesized by CCTP show that only one sharp peak appears at 283 C., which presents the degradation resulting from the random scission of the backbone and the terminal double bonds. GPC was carried out to analyze molecular weight information of copolymers synthesized in different conditions. Results illuminated that average molecular weight decreased with the increase of CoBF. Apparent chain transfer constants (C,) were determined with the conventional Mayo procedure based on number (Ma) and weight (Mw) average molecular weights, and with chain length distribution procedure based on peak (? P) and high (? H) molecular weight slopes. It could be found that the apparent chain transfer constants determined from Mw and Ar were similar and much better than others. In addition, on the basis of different monomer feed compositions, we found that C, values were increased with the concentration of MPS.