Synthesis of poly(cyclodiborazane)s by hydroboration polymerization using mesitylborane

Novel methodology for the preparation of poly(cyclodiborazane) was explored by hydroboration polymerization of dicyano compounds with mesitylborane. This method provides a useful way to prepare high molecular weight poly(cyclodiborazane) under mild reaction conditions. Hydroboration polymerization between adiponitrile and mesitylborane was examined under various conditions. As a result, the best condition was optimized to be adding a tetrahydrofuran solution of mesitylborane to adiponitrile at 0 degrees C and gradually warming up the reaction mixture to room temperature. The gel permeation chromatographic analysis showed that the number average molecular weight of the resulting polymer was 12000. Hydroboration polymerization by using various dicyano compounds was also examined. It was found that both aliphatic and aromatic dicyano compounds gave the corresponding polymers having relatively high molecular weights irrespective of the kinds of monomers employed.