Radiolytically Induced Polymer Formation in Alkenyl Carboranes: Phase Effects

The primary concern of this investigation has been to determine the effects of the physical state of structurally similar alkenyl substituted carborane monomers on their γ-ray induced polymerization. In the course of the investigation it was shown that I-vinyl-o-carborane apparently exhibits mesomorphic behavior at room temperature. This behavior was isotropic and most probably plastic crystalline in nature, whereas 1-isopropenyl--o-carborane exhibited only crystalline behavior below its capillary melting point. In the case of 1-vinyl-o-carborane it was shown that polymerization occurs in a “head to tail” manner with a high yield of polymer up to 11–12 units in length. Under the same conditions it was found that 1-isopropenyl--o-carborane gave rise to two dimer products which were structurally different. The dimerization of 1-isopropenyl--o-carborane appears to be topotatic in nature. The results of this study indicated that the physical state of the monomer has a pronounced effect both qualitatively and quantitatively on the γ-ray induced polymerization of these compounds.