Properties of liquid crystal oligomer blends of hydroquinone with flexible spacer

Abstract

In the present study thermal transition behavior, crystallization kinetics and crystal structure through X-ray diffraction patterns were investigated for the oligomers and oligomer blends of smectic and nematic oligomers. Three kinds of monomers were prepared (SP10, NP6, NP10 monomer) from decanediol, hexanediol and hydroquinone and p-hydroxybenzoic acid. And by reacting the monomers with TPC in various stoichiometric reactant ratio, three kinds of oligomers (SP10, NP6, NP10 oligomer) having various molecular weight as well as homopolymers were prepared, and for the comparison of X-ray pattern with the prepared blend a kind of block copolymer was prepared. For the prepared oligomers, homopolymers and blends, $T_m$, $T_i$, $T_c$ and $T_{deiso}$ were measured by DSC and polarizing microscope. The $T_m$ and $T_i$ increased as M.W increased. To obtain informations on the crystal growth, the Avrami exponents based on constant nucleation density were calculated using isothermal DSC method. Avrami exponent changed from 2 to 3 as the molecular weight of the SP10-oligomer increased, 1 to 2 as molecular weight of the NP6-oligomer increased. The Wide-Angle and Small-Angle X-ray diffractograms and photographs for quenched (from their liquid crystal state) powder samples were analyzed to obtain the inter-chain distance in their liquid crystal state. The crystallinity was low and inter-chain distance in the mesophase was in the range of $4-6 \mbox{\AA}$, and no significant differences were observed in diffraction patterns of oligomers and homopolymers. small-angle was nearly the same or a little smaller than the fully extended chain length.