Abstract
The second harmonic genarations of the liquid crystalline main-chain type copolymers of 2-hydroxy-6-naphthoic acid (HNA) with 4-hydroxy-benzoic acid (PHB), with various composition ratios were investigated. SHG of the films was greatly affected not only by polymerization conditions but also by the processing conditions of the films. NLO coefficient d_<exp> of electrically oniented sample is 3-5 times larger than that of mechanically oriented sample (5pm/V). The investigation on the relation between molecular compositions and the hyperpolarizability ( β ) performed by Molecular Orbital Methods clearly supports the idea that the high SHG of a main-chain polymer is mainly originated the additivity of β value of individual unit due to head to tail connection.
