CHAIN TRANSFER BY ADDITION FRAGMENTATION MECHANISM .5. RADICAL POLYMERIZATION OF VINYL MONOMERS IN THE PRESENCE OF ETHYL 2-[1-(TRIMETHYLSILYLPEROXY)ETHYL]PROPENOATE AND RELATED-COMPOUNDS

Ethyl 2-[1-(trimethylsilylperoxy)ethyl]propenoate 1, ethyl 2-[1-(dimet hylvinylsilylperoxy)ethyl]propenoate 2, ethyl lperoxysilyl)-1-methylet hylperoxy)ethyl]propenoate 3, and 2-phenyl-2-trimethylsilylperoxypropa ne 4 were synthesized and added to the free radical polymerization of vinylic monomers. 1 and 2 were found to show no homopolymerizability b ut act as effective chain transfer reagents in radical polymerizations of methyl methacrylate (MMA), styrene (St), and n-butyl acrylate (BA) . The estimated chain transfer constants (C-tr) are as follows: C-tr ( 1) = 0.15 for MMA, 0.90 for St, and 2.03 for BA at 60 degrees C; C-tr (2) = 0.12 for MMA, 1.16 for St, and 1.9 for BA at 60 degrees C. H-1-N MR spectra of poly(St) formed in the presence of 1 is consistent with the view that the polymers bear an oxirane at one terminal and an trim ethylsilyloxy fragment at the other end. Moreover, peroxysilane 4 show ed very low transfer properties by direct homolytic substitution (SH2) . These findings indicate that the ethyl 2-[1-(substituted dimethylsil ylperoxy)ethyl]propenoates 1-3 undergo chain transfer reaction via a i ntramolecular homolytic substitution (SHi) following an addition proce ss. Preparation of poly(styrene) up to high conversion in the presence of 3 yielded to the formation of the corresponding polymeric structur es bearing hydrolysable C-O-Si-O-C bonds. (C) 1996 John Wiley & Sons, Inc.