A solvent-free method for the hydrosilylation of pendant double bonds in block copolymers is reported in this article. An anionically prepared block copolymer, poly(styrene-b-1,2-butadiene), was heated with 1H,1H,2H,2H-perfluorooctyldimethyl-hydrosilane in the presence of a nonacidic platinum catalyst for 24-26 h to obtain a quantitatively hydrosilylated block copolymer. Gel permeation chromatography, IR, and thermogravimetric analysis were used to characterize the block copolymers obtained. © 2000 John Wiley & Sons, Inc.