ISSN:
0887-624X
Schlagwort(e):
chain transfer
;
addition-fragmentation
;
peroxysilane
;
radical polymerization
;
Chemistry
;
Polymer and Materials Science
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Chemie und Pharmazie
Notizen:
Ethyl 2-[1-(trimethylsilylperoxy)ethyl]propenoate 1, ethyl 2-[1-(dimethylvinylsilylperoxy)-ethyl]propenoate 2, ethyl 2-[1-(1-(2-ethoxycarbonyl-1-methyl-2-propenylperoxysilyl)-1-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 (Ctr) are as follows: Ctr (1) = 0.15 for MMA, 0.90 for St, and 2.03 for BA at 60°C; Ctr (2) = 0.12 for MMA, 1.16 for St, and 1.9 for BA at 60°C. 1H-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 (SH2). These findings indicate that the ethyl 2-[1-(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(SINGLE BOND)O(SINGLE BOND)Si(SINGLE BOND)O(SINGLE BOND)C bonds. © 1996 John Wiley & Sons, Inc.
Zusätzliches Material:
2 Ill.
Materialart:
Digitale Medien
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