Side-chain liquid-crystalline polymers based on flexible rod-like mesogen directly attached to backbone

Abstract

In this article, we report the synthesis and characterization of a new end-on side-chain liquid crystalline polymer (SCLCP), poly[4-(4′- alkoxyphenyloxymethylene)styrene] [denoted as Poly(n-POMS), where n is the carbon number of the alkyl tail, n = 2, 4, 6, 8, 12, 16], with the flexible rod-like mesogenic side-chain directly attached to the polymer backbone without flexible spacer. The polymer was obtained by using free radical polymerization. The chemical structures of Poly(n-POMS) and the corresponding monomer were characterized using various techniques with satisfactory analysis data. A combination analysis of differential scanning calorimetry, polarized light microscopy, small angle X-ray scattering, and wide-angle X-ray diffraction has been conducted to investigate the phase behavior of Poly(n-POMS). Poly(2-POMS), Poly(4-POMS), and Poly(6-POMS) are amorphous. Poly(8-POMS) develops partially into the liquid crystal phase, and Poly(12-POMS) and Poly(16-POMS) self-assembly into the smectic A (SmA) phase. Upon increasing temperature, the phase transition of Poly(16-POMS) follows the sequence of SmA1 ↔ SmA2 ↔ isotropic (I), which may be attributed to the conformation isomerization of the flexible rod-like mesogens. © 2012 Wiley Periodicals, Inc.