Structure development in simple cross-linked organopolysiloxanes
UNSPECIFIED. (1998) Structure development in simple cross-linked organopolysiloxanes. JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY, 13 (1-3). pp. 379-383. ISSN 0928-0707Full text not available from this repository.
C-13 CP and CPPI MAS NMR have been carried out on thermally cured samples of polymethylvinylsiloxane and polydimethylsiloxane. By varying the CP contact time, the alpha and beta vinyl carbons and the methyl carbon of the CH3-(SiO<)-CH=CH2 species could be identified. A further methyl carbon was detected which was less mobile and which we assign to methyl groups attached to silicon species on which the vinyl group has reacted to form a cross-link. Resonance from -CH2- carbons was observed in the 30-40 ppm range, and these species arise from methyl-vinyl cross-linking to give CH3-(SiO<)-CH2-CH2-CH2-(SiO<)-CH=CH2. Higher temperature curing promotes vinyl-vinyl cross-linking to give CH3-(SiO<)-CH2-CH=CH-CH2-(SiO<)-CH3 links between chains. Evidence for this comes from the insensitivity of the beta carbon resonance under CPPI, indicating that it is in a -CH= rather than a =CH2 environment. There was also evidence of -CH2- carbons in the polydimethylsiloxane material, suggesting that thermally activated, methyl-methyl cross-linking can occur to give CH3-(SiO<)-CH2-CH2(SiO<)-CH3 links between chains.
|Item Type:||Journal Article|
|Subjects:||T Technology > TP Chemical technology|
|Journal or Publication Title:||JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY|
|Publisher:||KLUWER ACADEMIC PUBL|
|Number of Pages:||5|
|Page Range:||pp. 379-383|
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