(Acta Polymerica Sinica) Near-Infrared-Responsive Copper Sulfide Nanoparticle/Liquid Crystal Elastomer Composites
writer：Ge, S.; Shan, Z.;Deng, L.; Lin, B.; Yang, H.*
keywords：liquid crystal
source：期刊
specific source：Acta Polymerica Sinica, 2017, 10, 1633-1640.
Issue time：2017年
In this manuscript, we report a novel near-infrared-responsive photothermal conversion reagent/liquid crystal elastomer composite material. Nowadays, most of the near-infrared absorbing inorganic metal nanoparticles can poison platinum and other precious metal catalysts, due to the chemical properties of these metal nanoparticles or their stabilizers (such as long chain thiols, quaternary ammonium salts, etc.), which cause the failure of using the classical Finkelmann two-step hydrosilylation reaction to prepare inorganic metal nanoparticle/liquid crystal elastomer composites. In order to solve this scientific problem, we apply a fast two-step thiol-ene photoaddition technology, embed near-infrared-responsive copper sulfide nanoparticles into liquid crystal elastomer matrix, and successfully fabricate a near-infrared-responsive monodomain copper sulfide nanoparticle/liquid crystal elastomer composite film for the first time. In detail, we first synthesize water-soluble CuS nanoparticles, and then exchange the sodium citrate stabilizer with poly(3-mercaptopropylmethylsiloxanes) (PMMS) to prepare oil-soluble CuS nanoparticles, which are mixed with PMMS, mesogenic monomers, crosslinkers and photoinitiators. The mixture is cast into a polytetrafluoroethylene mould and UV-illuminated at room temperature for 3 minutes to provide a pre-crosslinked liquid crystal elastomer composite film, which is further hung up and uniaxially stretched. The suspended pre-crosslinked liquid crystal elastomer film is UV-irradiated once more at room temperature for another 15 minutes, to accomplish the second thiol-ene photo-crosslinking stage to obtain the monodomain copper sulfide nanoparticle/liquid crystal elastomer composite film. This composite material is throughly investigated by using ultra-violet spectroscopy, transmission electron microscopy, polarized optical microscope, differential scanning calorimmetry, and one-dimensional X-ray scattering. The experimental results turn out that this composite sample has a room-temperature nematic liquid crystal phase and achieves a high-quality monodomain alignment. Most importantly, this composite film can perform a fast and reversible two-dimensional shrinking motion under the irradiation of 980 nm near infrared light. This novel copper sulfide nanoparticle/liquid crystal elastomer composite material might have potential applications in soft actuators and biomemetic technologies.