Supramolecular nano-assemblies from self-assembly of ABC coil-rod-coil triblock oligomers: Construction of tetragonal perforated lamellar and columnar nano-structures

Abstract

In this article, we report the self-assembling behavior of ABC coil-rod-coil triblock molecules 1a-1c and 2a-2c, containing biphenyl and phenyl units connected with ether and ester bonds as a rod segment and poly(propylene oxide)s (PPO) with a degree of polymerization (DP) of 7, 12 and 17 as a A block and octyl or hexadecyl alkyl chains as a C block of the coil segments. The supramolecular nanostructures of these molecules were characterized by a combination of techniques consisting of differential scanning calorimetry (DSC), thermal polarized optical microscopy (POM), and small-angle X-ray scattering (SAXS) measurement in the bulk state. Molecule 1a composed of PPO with a DP of 7 and a octyl alkyl chain as coil segment, self organize into unusal tetragonal perforated lamellar (TPL) and bicontinuous cubic (BCC) structures in the solid state and the liquid crystalline phase, respectively. While, molecule 2a consisting of same PPO coil as 1a and a hexadecyl alkyl chain, self assemble into TPL and BCC nano-structures in the crystalline phase. Meanwhile, molecules 1b-2b and 1c-2c incorporating longer PPO coil chains than 1a and 2a, self assemble into the columnar nano-structures in the solid state and liquid crystalline phase. These results clearly implied that self-organizing behavior of such molecules was dramatically influenced by the length of the PPO and alkyl coil chains connected with the rigid rod building block.