An Azoester-containing Photoresponsive Linear Liquid Crystal Polymer with Good Mesophase Stability

Photoresponsive linear liquid crystal polymers(LLCPs)are attractive because of the excellent stimuli-responsibility and the good processability.In this study,a new photoresponsive LLCP containing azoester(PC11AE6)with good mesophase stability was synthesized by ringopening metathesis polymerization.By introducing photoresponsive azoester mesogenic unit,which has high rigidity and a large lengthdiameter ratio,the resultant polymer possesses a broad mesophase temperature interval(isotropic temperature=180℃).A study on mesophase by 2D-wide angle X-ray diffraction indicated that the mesogens were orientated spontaneously into smectic A phase after annealing.The orientated films and fibres exhibited macroscopic,rapid and reversible deformations under light irradiation as a result of the photoisomerization of azoester as confirmed by UV-Vis absorption spectrophotometry.We anticipate that this work provides a strategy for preparing LLCP with a broad mesophase temperature range,which is positive for potential applications.

Synthesis of an Azobenzene-containing Main-chain Crystalline Polymer and Photodeformation Behaviors of Its Supramolecular Hydrogen-bonded Fibers

The synthesis of a new azobenzene(azo)-containing main-chain crystalline polymer with reactive secondary amino groups in its backbone and photodeformation behaviors of its supramolecular hydrogen-bonded fibers are described. This main-chain azo polymer(namely Azo-MP6) was prepared via first the synthesis of a diacrylate-type azo monomer and its subsequent Michael addition copolymerization with trans-1,4-cyclohexanediamine under a mild reaction condition. Azo-MP6 was found to have a linear main-chain chemical structure instead of a branched one, as verified by comparing its ~1H-NMR spectrum with that of the azo polymer prepared via the polymer analogous reaction of AzoMP6 with acetic anhydride. The thermal stability, phase transition behavior, and photoresponsivity of Azo-MP6 were characterized with TGA,DSC, POM, XRD, and UV-Vis spectroscopy. The experimental results revealed that it had good thermal stability, low glass transition temperature,broad crystalline phase temperature range, and highly reversible photoresponsivity. Physically crosslinked supramolecular hydrogen-bonded fibers with good mechanical properties and a high alignment order of azo mesogens were readily fabricated from Azo-MP6 by using the simple melt spinning method, and they could show "reversible" photoinduced bending under the same UV light irradiation and good anti-fatigue properties.