New Synthetic Methods for Silicon-Nitrogen Polymers.

摘要

If phenothiazine is present in the monomer mixture, arylenedisilanols and cyclosiloxazanes, with p-phenylenebis(methylvinylsilanol) present to insure crosslinking sites, provide polymers with inherent viscosities up to 3.5 dl/g. The polymers can be compounded and cured by conventional procedures. Condensation products of oxydi-p-phenylenebis(dimethylsilanol) and cyclosiloxazanes were studied in detail and elastomers with ultimate tensile strengths of 600-800 psi and 50-150% elongation at break were obtained. Some polymers were also prepared from p-phenyl-enebis(dimethylsilanol). Depending on the particular structure the polymers retained 15-70% of their strength after 24 hr at 250 C in a closed vessel and 60-80% of their strength after 500 hr in a circulating air oven at 260 C. Exposed to water-saturated air at 65-95 C for 500 hr they retained 45-65% of their strength. Brittle points as low as -100 C were obtained. The first event in the thermal decomposition of these polymers in air is methyl group oxidation. The polymer with the widest range of useful properties was prepared from p-phenylenebis(dimethylsilanol) and decamethyl-1,5-dioxa-3,7-diaza-2,4,6,8-tetrasilacyclooctane. Polymers from arylene-disilanols and cyclodisilazane monomers either gave very low strength elastomers or could not be cured. Improved methods of synthesis for a number of the monomers are reported. (Author)