| abstract |
The invention relates to crosslinked organopolysiloxanes useful as free radical macroinitiators for grafting polymerization of ethylenically unsaturated monomers. The organopolysiloxanes contain groups which form free radicals and are built up from units of the formula [RaSi(O(3-a)/2)-R1-X-(R1-Si(O(3-a)/2))bRa] (1), in which X is a radical from the group consisting of -N=N-, -O-O-, -S-S- and -C(C6H5)2-C(C6H5)2-, and R is monovalent SiC-bonded, optionally substituted C1- to C18- hydrocarbon radicals, R1 is divalent SiC-bonded, optionally substituted C1- to C18- hydrocarbon radicals which can be interrupted by divalent radicals, bonded to carbon atoms on both sides, from the group consisting of -O-, -COO-, -OOC-, -CONR2-, -NR2CO- and -CO-, R2 is a hydrogen atom or a radical R, a has the values 0, 1 or 2 and b has the values 0 or 1, and further organosiloxane units. |