Novel optically transparent polyesters containing a high density of second-order non-linear optically active chromophores

Abstract

The syntheses and second-order non-linear optical (NLO) properties of novel types of optically transparent polyesters containing a high density of second-order NLO-active chromophores are described. The chromophores used in this study contained either a perfluorooctyl- or an octyl-sulfonyl moiety as the electron-withdrawing group at the π-conjugating sites. The polyesters are prepared by condensation polymerization between isophthalic acid derivatives and 2-[N-(2-hydroxyethyl)-4-(perfluorooctylsulfonyl)anilino]ethanol by the use of triphenylphosphine and diethyl azodicarboxylate as the condensation reagents. The amorphous polyesters obtained, the optical transparency of which was down to 390 nm, exhibited good solubility in common organic solvents and provided optical-quality films by spin-coating. In addition, second-harmonic generation (SHG) measurements of spin-coated films of the polyesters were carried out by the Maker fringe method using a Q-switched Nd : YAG laser as the exciting beam after poling treatment. One of the polyesters, which was prepared from 5-{2-[N-methyl-4-(perfluorooctylsulfonyl)anilino]ethoxy}isophthalic acid and 2-[N-(2-hydroxyethyl)-4-(perfluorooctylsulfonyl)anilino]ethanol, exhibited the desired optical-transparency and a second-order NLO coefficient, d₃₃, of 3.0 pm V^–1.