A new class of second-order non-linear optical material: stilbazolium benzimidazolate covalently bound to polymer backbone

Abstract

This paper describes the first example of the preparation of stilbazolium benzimidazolate covalently bound to polymer backbone using a novel methacrylate monomer, 2-{4-[2-(4-methacryloyloxyphenyl)ethenyl]pyridinio}benzimidazolate. A free radical copolymerization of 2-{4-[2-(4-methacryloyloxyphenyl)ethenyl]pyridinio}benzimidazolate (1 equiv.) with butyl methacrylate (6 equiv.) provided a methacrylate polymer containing 1.7 mol% of betaine units. The resulting polymer exhibited a glass transition temperature of 30 °C. The number-average (M _n ) and weight-average (M _w ) molecular masses were 36 900 and 79 300, respectively, estimated by GPC measurement. The second-order non-linear optical property of the obtained polymer was investigated by second-harmonic generation (SHG) measurements applying the Maker fringe method using a Q-switched Nd:YAG laser (1064 nm) as an exciting beam after corona-poling, indicating that the d ₃₃ value of the resulting copolymer was 5.1 pm V ^-1 .