Synthesis and properties of diarylsiloxane and (aryl/methyl)siloxane polymers

olydiarylsiloxanes are highly crystalline, high melting polymers with excellent high temperature properties. The polymers of greatest interest in this investigation have been those containing phenyl and p-tolyl substituents on the siloxane backbone. We have prepared a series of polymers with various combinations of these substituents, as well as the end members of the series, polydiphenylsiloxane and polydi(p-tolyl)siloxane. The polymers are prepared with controlled molecular weights and distribution by ring-opening anionic polymerization of the cyclic trimers in solution.;The crystal ;The solution properties of three different types of poly(phenyl/p-tolyl)siloxanes have been investigated in order to characterize the chain stiffness properties. The Mark-Houwink-Sakurada exponents, "a", for these polymers are between 0.75 and 0.86. The values of these exponents are below the values expected for a rigid chain (a ;In addition to the phenyl and p-tolyl siloxane polymers, other diarylsiloxane polymers have been synthesized and characterized. The crystal...