A polyorganosiloxane polymer having a structure represented by one of the formulas(AB).sub.m C or [(AB).sub.m ].sub.n SiR.sub.(4-n)where the R groups are the same or different organic groups other than acrylic groups or groups co-curable therewith; A is a linear polyorganosiloxane segment containing between 3 and about 50 siloxane repeat units at least 3 of which are acrylic groups containing repeat units represented by the formula ##STR1## where R.sup.1 is H or lower alkyl, R.sup.2 is alkylene or alkenylene, and y is 0-4; B is a polyorganopolysiloxane segment represented by the formula ##STR2## where x is an integer of at least 100; C is A or a triorganosilyl group; m is an integer of 1 or more; and n is 3 or 4.