Topochemical polymerization of dumbbell-shaped diacetylene monomers: relationship between chemical structure, molecular packing structure, and gelation property.

ABSTRACT

Herein, we have synthesized novel photopolymerizable dumbbell-shaped diacetylene liquid crystal (LC) monomers by locating a diacetylene dicarboxylic acid group at the center and chemically connecting swallow-tails, such as hydrophobic alkyl chains (abbreviated as AT3DI) and amphiphilic biphenyl mesogens (abbreviated as BP3DI), with bisamide groups. Major phase transitions of dumbbell-shaped diacetylene monomers were identified using differential scanning calorimetry (DSC), polarized optical microscopy (POM), and Fourier transform infrared spectroscopy (FT IR). Molecular packing structures were studied based on structure-sensitive wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS) analyses. Mainly, due to nanophase separations and strong intermolecular hydrogen bonding, AT3DI formed a low-ordered lamellar LC phase at room temperature. BP3DI self-assembled into highly-ordered crystal phases (K1 and K2) at lower temperatures below a low-ordered lamellar LC phase, in which BP3DI were intercalated with each other to compensate the mutual volume differences. From the photopolymerization of AT3DI and BP3DI, it was realized that the topochemical reactions of dumbbell-shaped diacetylene monomers were closely related to their chemical structures as well as molecular packing structures.