Reversible microscale assembly of nanoparticles driven by the phase transition of a thermotropic liquid crystal

The arrangement of nanoscale building blocks into patterns with microscale periodicity is challenging to achieve via self-assembly processes. Here, we report on the phase transition-driven collective assembly of gold nanoparticles in a thermotropic liquid crystal. A temperature-induced transition from the isotropic to the nematic phase leads to the assembly of individual nanometre-sized particles into arrays of micrometre-sized aggregates, whose size and characteristic spacing can be tuned by varying the cooling rate. This fully reversible process offers hierarchical control over structural order on the molecular, nanoscopic, and microscopic level and is an interesting model system for the programmable patterning of nanocomposites with access to micrometre-sized periodicities.

Improved cationic dyeability of thermotropic liquid crystal polyarylate fabrics by ultraviolet irradiation-induced grafting of acrylic acid

As one of the most promising high-performance fibers, it is worthwhile to investigate the dyeing property of thermotropic liquid crystal polyarylate (TLCP) fibers. In this work, ultraviolet (UV) irradiation-induced grafting using the acrylic acid (AAc) method was employed to improve the cationic dyeability of the TLCP fabrics. The TLCP fabrics were firstly immersed in an AAc monomer solution for 24 h, followed with the UV radiation process for grafting polymerization. The results showed that the dyeing performance to C.I. Basic Red 46 of the modified TLCP fabrics was remarkably improved. Through several characterizations, it was found that the AAc-grafted TLCP fibers became more roughened with many pits on the fiber surface, while the crystalline structure of the TLCP fibers was hardly affected. More importantly, carboxyl groups have been successfully introduced onto the TLCP fiber surface, which is the main reason for the good dye uptake. Therefore, this paper provides a simple and efficient way for the improvement of the cationic dyeing property of TLCP fabrics.

Effect of 2-phenoxyethanol pre-treatment on structure and adhesion properties of thermotropic liquid crystal polyarylate fibers

This study investigated the surface modification of thermotropic liquid crystal polyarylate (TLCP) fibers by 2-phenoxyethanol pre-treatment, specifically, whether it enhanced their interfacial adhesive properties. The surface chemical compositions and microstructures of both control and 2-phenoxyethanol pre-treated TLCP fibers were characterized by X-ray photoelectron spectroscopy, scanning electron microscopy, and atomic force microscopy. Furthermore, thermal, dyeing, and adhesion properties of both control and 2-phenoxyethanol pre-treated fibers were compared by thermogravimetric analysis, colorimetry, and universal material testing system, respectively. The results indicated that 2-phenoxyethanol pre-treatment increased the surface-anchored oxygen atom amount: the oxygen to carbon atomic ratio at the surface of the TLCP fibers increased from 0.17 to 0.22. However, 2-phenoxyethanol pre-treatment showed almost no effect on the thermal stability and mechanical properties of the TLCP fibers. The peeling strength of the 2-phenoxyethanol pre-treated TLCP fabric was around twice that of the control TLCP fabric.

Temperature-induced liquid crystal microdroplet formation in a partially miscible liquid mixture

We demonstrate how, for a binary blend of a thermotropic liquid crystal and methanol, cooling from a miscible to an immiscible state induces the reversible formation of microdroplets, whose size, number and mesogen orientation can be controlled by the temperature protocol.