Nine poly(carborane-siloxane) high temperature elastomers which differ systematically in chemical structure were investigated by Torsional Braid Analysis. The structural variations include two different carborane cage structures in the polymer chain ( -CB10H10C- and -CB5H5C- ) and the step-wise increase in the number of -Si(CH3)2-O- linkages associated with each cage in the repeat unit. Polydimethyl-siloxane was studied as the compositional limit of both series. The dynamic mechanical relaxations (about 1 cps) of the materials are reported. These include the melting points of the semi-crystalline polymers, and the glass transitions and secondary transitions of all the polymers. The glass transition temperatures in each series were systematized using a well known copolymer composition versus glass transition temperature relationship. (Author).