Synthesis and characterization of (2R, 3R)-(+)-diethyl tartrate-based chiral polyesters designed for second harmonic generation

Abstract

A novel synthetic approach has been devoleped to incorporate donor-acceptor substituted π-conjugated segments and chiral centres in main-chain polymeric systems. A series of optically active main-chain polyesters were synthesized by high-temperature polycondensation from biphenolic azo chromophores, (2R,3R)-(+)-diethyl tartrate, and terephthaloyl chloride. The biphenolic chromophores were bis(4-hydroxyphenylazo)-2,2′-dinitrodiphenylmethane and bis(4-hydroxyphenylazo)-2,2′-dinitrodiphenylsulfone. The effects of solvent, reaction time, and temperature on the polymerization were investigated. The optical activity of the polymers showed that the introduction of a substantial amount of chiral groups in the polymer chain leads to the formation of non-centric configurations. The chiral order was found to be thermally stable. The polyesters showed glass transition temperatures in the range 100–190°C and were thermally stable up to 350°C. All polyesters showed positive solvatochromism in UV–visible absorption spectra.

Keywords:

• polyesters
• chirality
• second harmonic generation
• solvatochromism