Synthesis and Characterization of Poly (L-lactic acid) Containing the Azobenzene Mesogens

摘要

A series of azobenzene containing group Poly (L-lactic acid) (PLLA) were synthesized by Ring-Opening Polymerization of L-lactide (L-LA) catalysted by Sn(Oct)_2 initiated by alcohol-OH containing the azobenzene chromophores. Their molecular weights were well controlled by the feed ratio as characterized by Gel Permeation Chromatography (GPC) and ~1H NMR Spectrometry and agreed well with theoretical values. The thermal properties and liquid crystal phases were investigated by Differential Scanning Calorimetry (DSC), polarized optical microscopy (POM) and X-ray Diffraction (XRS) measurements. Cis-trans photoisomerization behavior of the polymers in the solutions and the films were studied with UV irradiation. By the Circular Dichroism Spectroscopy (CD) characterization of the solutions and films of the polymer, the PLLA segments show huge optical rotation power in helical structure.