SELECTIVE PHOTO-CROSS-LINKING OF MICROPHASE-SEPARATED MULTIBLOCK COPOLYMERS OF POLY(DIMETHYLSILOXANE) AND PHENYLENE DIACRYLATE POLYESTERS

New multiblock copolymers based on dimethylsiloxanes and phenylene dia crylate derivatives have been prepared by hydrosilation polymerization . Copolymerization was performed using either low molecular weight mon omers or high molecular weight macromers. The organic macromer was pre pared by acyclic diene metathesis (ADMET) polymerization of para-pheny lenediacrylic acid dipent-4-enyl ester. Hexamethyltrisiloxane and alph a,omega-bishydride-terminated polydimethylsiloxane (PDMS) were used as inorganic macromers. The copolymers show microphase separation of the soft siloxane block and the hard semicrystalline organic block, as ob served by differential scanning calorimetry (DSC), X-ray scattering ex periments (SAXS and WAXS) and transmission electron microscopy (TEM). The crosslinking rate upon UV-irradiation is slightly higher for the m icrophase-separated copolymer than for the corresponding homopolymer. When films of the polyester-PDMS multiblock copolymers were irradiated with linearly polarized light, optically anisotropic films were obtai ned with a polarizing efficiency of 67%, whereas the crosslinked films of the homopolymer had a polarizing efficiency of at most 43%.