Futao Cheng

Photoinduced bending behavior of crosslinked liquid-crystalline polymer films with a long spacer

An acrylate monomer and diacrylate crosslinker containing a spacer of undecylene were synthesized and crosslinked liquid-crystalline polymer films with different crosslinking densities were prepared by photopolymerization of mixtures of the monomer and the crosslinker. Due to the relatively long spacer, distinct bending behavior was observed in the film with a low crosslinking density: when the temperature was lower than 90 °C, the film first bent away from the light source and then towards it upon the irradiation of UV light. As the temperature was raised above 90 °C, the film bent directly towards the light source. X-ray diffraction was used to probe the phase structures of the film at different temperatures and a plausible mechanism was presented to explain the distinct phenomenon. In addition, when the crosslinking density was increased, all the films bent directly towards the light source with faster speed, which is related to their modulus and order parameters.

Light-controlled quick switch of adhesion on a micro-arrayed liquid crystal polymer superhydrophobic film

A micro-arrayed liquid crystal polymer film, cross-linked in the nematic phase, was successfully prepared from an optimized azobenzene precursor and polydimethylsiloxane-soft-template-based secondary replication. Regulated by alternating irradiation of UV-visible light (365 nm/530 nm), the micro-arrayed film showed an ideal quick (<1 min) and reversible switch of superhydrophobic adhesion.

Light-responsive actuation materials based on the photodeformable liquid crystal polymers

Two acrylate monomers and two diacrylate crosslinkers containing a long spacer were synthesized and crosslinked liquid-crystalline polymer (CLCP) films with different concentrations of azobenzene were prepared by photopolymerization of the mixtures of the monomers and the crosslinkers. All the monomers, crosslinkers and polymerizable mixtures exhibited LC phases in heating or/and cooling processes. Due to the relatively long spacer, the obtained CLCP films exhibited a glass transition around 30 °C, which allows the CLCP films to undergo photodeformations at room temperature. In addition, when the concentration of azobenzene decreased, the films bent towards the light source with a faster speed and a larger photoinduced mechanical force.

Light-Driven Soft Actuator Materials Based on Liquid-Crystalline Polymers

Various kinds of crosslinked liquid-crystalline polymers were synthesized with acrylate monomers and diacrylate cross-linkers containing azobenzene moieties. The effect of spacer length on photoinduced bending behavior of the polymer films was investigated. The films with long spacers exhibited low glass transition temperatures and underwent bending and unbending behavior at room temperature. Mechanical force generated during the process of UV light irradiation was also measured. It was found that the maximum force increased with the increment of the cross-linking density and the intensity of UV light.

Photoinduced Deformation of Liquid Crystal Polymers

Utilizing an optimized azobenzene precursor and polydimethylsiloxane-soft-template-based secondary replication, we achieved light-driven switching of superhydrophobic adhesion of water droplets on a micro-arrayed liquid crystal polymer film, which is cross-linked in nematic phase and guarantees a satisfying stability for practical application. Regulated by alternating irradiation of UV-Vis light (365 nm/530 nm), the micro-arrayed film showed an ideal quick (< 1 min) and reversible switch of superhydrophobic adhesion. This kind of non-contact real-time controllable switching of microdroplet’s adhesion might inspire and facilitate the designs and applications in novel microfluidic devices.