BLOCK-COPOLYMERS WITH LOW SURFACE-ENERGY SEGMENTS - SILOXANE-MODIFIEDAND PERFLUOROALKANE-MODIFIED BLOCKS

In this paper we describe the preparation and preliminary characteriza tion of diblock copolymers with a low surface energy block. These poly mers were prepared by modifying the isoprene block in styrene-isoprene -based block copolymers with either short perfluoroalkyl or dimethyl s iloxy 'fingers'. Specifically, the diene block of a styrene-isoprene b lock copolymer containing a large proportion of pendent vinyl groups ( 1,2- and 3,4-isoprene) was reacted with the appropriate hydrosilane in the presence of non-acidic Pt catalyst. The degree of attachment of h ydrosilane was as high as 50% of the pendent unsaturations. Pendent vi nyl groups were converted more efficiently than pendent methyl vinyl g roups. These block copolymers, when mixed with the styrene homopolymer , exhibited surface segregation behaviour which depended on both polym er molecular weight and processing conditions. The surface segregation properties of the resulting block copolymers were studied by a variet y of techniques which include contact and either X-ray photoelectron s pectroscopy or Rutherford backscattering spectrometry. Contact angles as high as 110 degrees were measured for both the siloxane- and perflu oroalkane-modified materials.