A new series of organoboranes. VII. The preparation of poly‐m‐carboranylenesiloxanes

Abstract

SynopsisThis paper describes the preparation of the first members of a new series of polysiloxanes characterized by having m-carborane nuclei in the backbone of the polymers. Although neither hydrolysis of 1,7-bis( chlorodialkylsilyl)-mcarborane monomers nor catalytic dehydration of the corresponding dihydroxy compounds would proceed to give the type of polysiloxanes desired, the polymers were readily prepared by the ferric chloridecatalyzed elimination of an alkyl halide from equimolar mixtures of dichloro-and dialkoxysilanes. This t,echnique allowed the systematic introduction of dialkylsiloxy groups between m-carborane nuclei. Characterization of the polymers is described as well as differential scanning calorimetry studies which show the prime members of the series to be thermally stable to 500°C. and oxidatively stable to about 350OC. CHICHI CH3

Boron-Containing Polymers—The Carboranesiloxanes

“…16 Polymers above I ,000-2,000 in molecular weight could not be prepared by the conventional route of hydrolysis of 1, 7 -bis( chloro-dimethylsilyl)m-carborane, this failure being ascribed to the extremely electronegative nature of the carborane nucleus. Success was achieved by ferric chloride-catalyzed elimination of an alkyl halide from equimolar mixtures of dichloroand dialkoxysilanes at temperatures of 140-165°C.…”

“…The earliest results using differential scanning calorimetry 16 showed that the polymers Dexsil 100, Dexsil 200, and Dexsil 300 were stable up to 500°C in an inert atmosphere. In air, however, only Dexsil 100 remained unchanged up to this temperature.…”

Thermal behavior of dimethyl‐m‐carboranyl–dimethylsiloxane copolymers

“…The endothermic and exothermic deflections are in good agreement with previously reported differential scanning calorimetric measurements made at 500°C. 4 On the basis of the DTA thermogram obtained from a dimethylpolysiloxane the initial exothermic change exhibited by the copolymers in the temperature region of 250-450°C. can be reasonably associated with the oxidation of methyl groups.…”

o-Carborane-Containing Poly(siloxane-arylacetylene)s With Thermal and Thermo-Oxidative Stabilities

“…Carboranes have been incorporated by various methods into polymers to improve oxidation resistance. In the 1960s, the first members of polysiloxanes with m-carborane units in the backbone of the polymers were prepared by the ferric chloride catalyzed elimination of an alkyl halide from equimolar mixtures of dichloro-and dialkoxysilanes (7). The polymers proved to be thermally stable to 500 C and oxidatively stable to about 350 C. In the 1970s, an alternating block copolymer containing m-carborane units was prepared by the reaction of a ureidosilane-terminated polysulfone hard block with a carboranesilanol-terminated carboranesiloxane oligomer (8).…”