Southeast University made a breakthrough in the research of photodeformation polymer materials

Recently, Prof. Yang Hong from the School of Chemistry and Chemical Engineering of Southeast University achieved a breakthrough in the research field of near-infrared photodeformation polymer materials. The research team developed the first example of a liquid crystal directly embedded in a near-infrared photothermal conversion group by chemical bonding. Elastomer material with ultra-fast response speed and super mechanical properties. The research results were recently published in the top international journal "American Journal of Chemistry".

Near-infrared light-induced deformation of polymer materials in the bionic devices, soft robots and other fields have a good application prospects. Conventional near-infrared photodeformation polymer materials are all physically doped, and photothermal conversion reagents, up-conversion luminescent materials, and the like are incorporated into a polymer (such as a liquid crystal elastomer, a hydrogel, etc.) substrate, and thus Under infrared light conditions, phase transformation, swelling and other effects of polymer materials are induced, resulting in photoinduced deformation. However, due to the presence of a solubility problem between the various reagents doped with the polymer substrate, it can lead to a dilemma: if the doping amount is too low, the photoresponse rate will be slowed, and if the doping amount is too high, the mechanical properties of the material will be reduced. .

The direct incorporation of near-infrared photothermal conversion groups in polymers by chemical bonding is the best solution to the above scientific problems. The research team of Southeast University designed a thiophene-ketocarotene molecule containing a four-armed alkenyl group, which has both near-infrared photothermal conversion effect as a cross-linking agent; and developed a two-step acyclic olefin metathesis polymerization The joint preparation strategy realizes a main chain type liquid crystal elastomer material that is directly embedded in the near-infrared photothermal conversion group by chemical bonding.

Because the content of near-infrared photothermal conversion groups in the system is as high as 17% by weight and uniformly dispersed, the liquid crystal elastomer material has an ultra-fast photoresponse speed, and is near 808 nm (0.83 W·cm−2). The temperature of the material system can be increased from room temperature to 260 oC in 8 seconds, and reversible light contraction can be achieved within 3 to 4 seconds. In addition, due to the structural design of the main chain liquid crystal elastomer, the material has excellent mechanical properties, and the elastic modulus of the isotropic phase can still be maintained at about 1.4 MPa, which is higher than the conventional side chain type liquid crystal elastomer. An order of magnitude; under near-infrared light, it can pull up 5680 times its own weight.

This work was funded by the National Natural Science Foundation of China (Project No. 21374016) and the Natural Science Foundation of Jiangsu Province (Project BK20170024). These academic papers were published in the journal of the American Chemical Society (Li Liu, Mei-Hua Liu, Lin-Lin). Deng, Bao-Ping Lin, Hong Yang.* "Near-Infrared Chromophore Functionalized Soft Actuator with Ultrafast Photoresponsive Speed ​​and Superior Mechanical Property". J. Am. Chem. Soc. 2017, 139, 11333-11336.). The first author of the dissertation was a 17th grade Ph.D. student (15 master), Liu Li. (Xu Zhaofei)