Poly(organophosphazenes) Containing Allyl Side Groups: Cross-Linking and Modification by Hydrosilylation

Harry R. Allcock, Dawn E. Smith, Young Baek Kim, John J. Fitzgerald

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24 Scopus citations

Abstract

Poly (organophosphazenes) containing 4-(allyloxy)phenoxy and 4-[4′- (allyloxy)phenyl]phenoxy side groups were synthesized and modified by hydrosilylation reactions. A small-molecule model compound, pentaphenoxy[4-(allyloxy)phenoxy]cyclotriphosphazene, underwent platinum-catalyzed hydrosilylation reactions with heptamethyltrisiloxane and dimethylethoxysilane. The product of the second reaction, containing one dimethylethoxysilane group, underwent hydrolysis and self-condensation reactions in the presence of acid. Transposition of this chemistry to the high-polymer level was then accomplished. Thus, hydrosilylation of phosphazene high polymers with allylaryloxy side groups yielded poly(organophosphazenes) with dimethylsiloxane side group graft units. High siloxane loadings were obtained without evidence of Si-O or Si-C bond cleavage. A series of polymers with 4–100% grafting of dimethylsiloxane segments (corresponding to 6.5–56.2% dimethylsiloxane by weight) were synthesized and characterized by DSC, TGA, and GPC. Two polymers were further characterized by DMA. Glass transition temperatures of the siloxane-containing polymers ranged from -79 to +20 °C, according to the amount of siloxane grafting and the nature of the other groups attached directly to the phosphazene polymer backbone. The siloxane-containing polymers also showed a relaxation at approximately -120 °C. This combined with SAXS data suggested that the dimethylsiloxane side group may exist in microphase-separated domains. Cross-linking of polymers that contained unsaturated groups was achieved by ultraviolet irradiation and γ-irradiation. Poly(organophosphazenes) bearing 20 and 46 mol % dimethylethoxysilane groups cross-linked readily on exposure to atmospheric moisture.

Original languageEnglish (US)
Pages (from-to)5206-5215
Number of pages10
JournalMacromolecules
Volume27
Issue number18
DOIs
StatePublished - Aug 1 1994

All Science Journal Classification (ASJC) codes

  • Organic Chemistry
  • Polymers and Plastics
  • Inorganic Chemistry
  • Materials Chemistry

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