Self-assembly of liquid crystal block copolymer PEG-b-smectic polymer in pure state and in dilute aqueous solution

TL;DR

This paper investigates the self-assembly behavior of amphiphilic liquid crystal block copolymers, revealing nano-structures in pure state and vesicle formation in aqueous solution, with detailed structural characterization.

Contribution

It provides detailed insights into the nano-structures and self-assembly mechanisms of LC block copolymers in different environments, including the formation of polymersomes with preserved smectic order.

Findings

Hexagonal cylindrical micro-segregation phase with 11.2 nm lattice distance

Formation of polymersomes with smectic order in aqueous solution

Layer spacing of 2.4 nm in the smectic polymer matrix

Abstract

A series of amphiphilic LC block copolymers, in which the hydrophobic block is a smectic polymer poly(4-methoxyphenyl 4-(6-acryloyloxy-hexyloxy)-benzoate) (PA6ester1) and the hydrophilic block is polyethyleneglycol (PEG), were synthesized and characterized. The self-assembly of one of them in both the pure state and the dilute aqueous solution was investigated in detail. Nano-structures in the pure state were studied by SAXS and WAXS on samples aligned by a magnetic field. A hexagonal cylindrical micro-segregation phase was observed with a lattice distance of 11.2 nm. The PEG blocks are in the cylinder, while the smectic polymer blocks form a matrix with layer spacing 2.4 nm and layer normal parallel to the long axis of the cylinders. Faceted unilamellar polymer vesicles, polymersomes, were formed in water, as revealed by cryo-TEM. In the lyotropic bilayer membrane of these polymersomes, the thermotropic smectic order in the hydrophobic block is clearly visible with layer normal parallel to the membrane surface.