Chain transfer by addition-fragmentation mechanism. VII. Radical polymerization of vinyl monomers in the presence of ethyl 2-[1-(trimethylsilylperoxy)ethyl]propenoate and related compounds
✍ Scribed by Daniel Colombani; Isabelle Beliard; Philippe Chaumont
- Publisher
- John Wiley and Sons
- Year
- 1996
- Tongue
- English
- Weight
- 781 KB
- Volume
- 34
- Category
- Article
- ISSN
- 0887-624X
No coin nor oath required. For personal study only.
✦ Synopsis
Ethyl 2-[ 1-(trimethylsilylperoxy)ethyl]propenoate 1, ethyl 2-[ 1-(dimethylvinylsilylperoxy)ethyllpropenoate 2, ethyl 2-[ 1-( l-(2-ethoxycarbonyl-l-methyl-2-propenylperoxysilyl)-l-methylethylperoxy)ethyl]propenoate 3, and 2-phenyl-2-trimethylsilylperoxypropane 4 were synthesized and added to the free radical polymerization of vinylic monomers. 1 and 2 were found to show no homopolymerizability but 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,) are as follows: C, (1) = 0.15 for MMA, 0.90 for St, and 2.03 for BA at 60°C; C, (2) = 0.12 for MMA, 1.16 for St, and 1.9 for BA at 60°C. 'H-NMR 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 trimethylsilyloxy fragment at the other end. Moreover, peroxysilane 4 showed very low transfer properties by direct homolytic substitution (SH,). These findings indicate that the ethyl 2-[ l-(substituted dimethylsilylperoxy)ethyl]propenoates 1-3 undergo chain transfer reaction via a intramolecular homolytic substitution (SHi) following an addition process. Preparation of poly(styrene) up to high conversion in the presence of 3 yielded to the formation of the corresponding polymeric structures bearing hydrolysable C -0 -Si -0 -C bonds.