HYDROBORATION POLYMERIZATION .2. SYNTHESIS OF ORGANOBORON POLYMERS BY THE REACTION BETWEEN DIYNE AND THEXYLBORANE

Synthesis of organoboron polymers by polyaddition between thexylborane (1) and diynes (2) is described. When a terminal diyne such as 1,7-octadiyne (2a) was used as a monomer, a moderate amount of cross-linking reaction occurred due to the dihydroboration of vinylborane units in the main chain of the polymer. Even when an organoboron polymer was prepared from a stoichiometric amount of 1 and 2a, the obtained polymer showed in H-1 NMR only 60% of vinyl protons on the basis of an assumption of linear structure. That is, the resulting polymer had 20% branched structure. As the result of the cross-linking reaction, gelation was observed when an excess amount of 1 was used. The gel obtained with the excess of 1, however, dissolved again by the treatment with methanol. On the other hand, when an internal diyne such as 3,9-dodecadiyne (2b) was used as a monomer, no gelation was observed even in the presence of an excess amount of 1. Little contribution of branched structure was detected by the spectroscopic analyses of the polymer prepared from an equimolar amount of 1 and 2b.