Preparation and thermal properties of asymmetrically substituted poly(silylenemethylene)s

✍ Scribed by Q. H. Shen; L. V. Interrante

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 219 KB
• Volume: 35
• Category: Article
• ISSN: 0887-624X
• DOI: 10.1002/(sici)1099-0518(19971115)35:15<3193::aid-pola12>3.0.co;2-6

✦ Synopsis

Poly(silylenemethylene)s of the types [SiMeRCH 2 ] n and [SiHRCH 2 ] n were prepared by the ring-opening polymerization (ROP) of 1,3-disilacyclobutanes (DSCBs) containing n-alkyl substituents, such as C 2 H 5 , n-C 3 H 7 , n-C 4 H 9 , n-C 5 H 11 , and n-C 6 H 13 , or a phenyl group on the Si. These new polymers include a monosilicon analog of poly(styrene), [SiHPhCH 2 ] n . Improved synthesis routes to the DSCB monomers were developed which proceed through Grignard ring closure reactions on alkoxy-substituted chlorocarbosilanes. All of these asymmetrically substituted polymers were obtained in high molecular weight form, except for [SiHPhCH 2 ] n . The configurations of all of the polymers were found to be atactic. The aryl-substituted polymers have higher glass transition temperatures (T g s) and thermal stability than those of the alkyl-substituted poly(silylenemethylene)s. Unlike the polyolefins of the type [C(H)(R)CH 2 ] n , where T g drops continuously from R Å Me to n-Hex, the T g s of the n-C n H 2n/1 (n Å 2-6)substituted [SiMeRCH 2 ] n PSM's appear to reach a maximum (at 061ЊC) for the R Å n-Pr-substituted polymer. Moreover, where it was possible to make direct comparisons among similarly substituted atactic polymers, all of the poly(silylenemethylene)s were found to have lower T g s than their all-carbon analogs.