The introduction of elastomeric behavior into polycarboranylenesiloxane SiB‐1 polymers from the closo‐carborane C2B5H7

The copolymerization of a small amount of the larger (C2B8 and C2B10) carboranes with the smaller C2B5 carborane resulted in the formation of an elastomeric SiB-1 carboranesiloxane, a polymer hitherto prepared only in crystalline form. Although the elastomeric behavior of the uncured SiB-1 copolymer decreased with time, curing stabilized the rubber by inhibiting crystallization.