| 摘要 |
<p>An improved method for the preparation of very high molecular weight polycarborane siloxane polymers in which each of the reactants is first provided in an ultra-pure state by a series of recrystallization procedures in specific solvents. The reactants are then reacted in the following series of steps by: (a) providing ultra-pure carborane bisdimethyl silanol in dried chlorobenzene solvent, to form a slurry and cooling said slurry to -10 +/- 5 DEG C; (b) adding to said slurry a mixture of ultra-pure dimethylbisureido silane and ultra-pure methylphenylbisureido silane to form a reaction mixture at -10 +/- 5 DEG C; (c) separating from said reaction mixture a silanol end-capped prepolymer of said polycarborane siloxane polymer; (d) dissolving said prepolymer in chlorobenzene to form a solution; and (e) adding to said prepolymer solution an excess of said ultra-pure bisureido silane selected from the group consisting of dimethylbisureido silane, methylphenylbisureido sane and a mixture thereof, to form said very high molecular weight polycarborane siloxane polymer. Alternatively, step (e) may be performed at 60 -70 DEG C to further increase the molecular weight of the polymer. In an alternative process, step (b) is performed at -15 to -20 DEG C for 6 to 20 hours and steps (c) through (e) are omitted.</p> |
