Photoactive liquid crystalline polymers: A comprehensive study of linear and hyperbranched polymers synthesized by A2 B2 , A2 B3 , A3 B2 , and A3 B3 approaches

Abstract

A series of linear and hyperbranched polyester epoxies, with varied structural parameters such as kinked structure and different dendritic architectures, were synthesized by A2 þ B2 ,A 2 þ B3 ,A 3 þ B2, and A3 þ B3 approaches. The structures of synthesized monomers and polymers were con- firmed by Fourier transform infrared, 1 H NMR, and 13 C NMR spectroscopic techniques. The effect of varied structural param- eters on phase behavior and photoresponsive properties was investigated by using differential scanning calorimeter, thermal optical polarized microscope, UV-visible spectroscopy, photo- viscosity, and refractive index studies. The transition tempera- tures of hyperbranched polymers were higher than that of the corresponding linear analogues. All the polymers showed ne- matic phase (nematic droplets) over a broad temperature range. The effect of kinked structural unit on photoresponsive property is less in both linear and hyperbranched architectures. Although the effect of architectural nature is highly consider- able within the hyperbranched architectures, the polymer (HPE-33) synthesized by A3 þ B3 approach showed highest rate of photocrosslinking, followed by HPE-I 32; HPE-T 32, and HPE-23, which were synthesized by A3 þ B2 and A2 þ B3 approaches, respectively. The findings in photoresponsive properties were further supported by molecular modeling stud- ies. Substantial variation of refractive index (0.015-0.024) indi- cates that these polymers could be used for optical recording. V C 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49: 1319-1330, 2011