Surface Modification of Liquid Crystal Polymers by Two Steps UV-Induced Graft Polymerization

High efficiently conducting Norrish II type UV-induced graft polymerization on fully aromatic liquid crystal polymers (LCPs) is still a great change due to its lack of sp3 hybridized C–H bonds. Here, a facile strategy for photograft modification of LCP film surfaces was developed. First, the LCP surface was modified by the UV-assisted aminolysis reaction to introduce H atoms that can be effectively abstracted by Norrish II type photosensitizers. Then, photograft polymerization of acrylic acid or styrene/maleic anhydride on the surface of modified LCP was achieved under UV irradiation by using benzophenone (BP) as a photosensitizer. The water contact angle of LCP decreased from 86° to 40° after being photografted with poly(acrylic acid) (PAA). The highest grafting density reached 7.78 × 10–2 mg/cm2, which is much higher than the unmodified LCP directly photografted with PAA (2.57 × 10–3 mg/cm2). The strategy showed excellent spatial controllability in preparation of the regionally modified LCP surface. Patterned polymer brushes of PAA and styrene-maleic anhydride copolymer could be introduced onto the surface of the LCP film with the help of a photomask, which were further used to selectively deposit a silver pattern by electroless plating and immobilize protein, respectively. The PAA-modified LCP deposited with the copper layer exhibited improved adhesive property with copper foil and had a peeling strength of 12.3 N/cm, which was much higher than the peeling strength of blank LCP (0.7 N/cm). This success of the two-step UV-induced graft surface modification of LCP has promising applications in the fields of high-speed electronic communication, biomedical materials, composite materials, and other fields.