. . "at least one half of all R groups are ???OR2; either at least one silicon atom of the oligomer has an R3 group thereon or at least one R is a B, or both; if there is a B group, the B group is non-terminal to the oligomer; if there is a group R3 which is a vinyl group, there is at least one other group on the oligomer which is a B group, an R3 group other than vinyl, or an R4 group: m=2 to 20; n=0" . .