Preparation And Property Of Light And Thermal Dual-Responsive Nanocomposite Hydrogel

Stimulus-responsive hydrogels can respond to the stimulation of specific environmental changes.Therefore,they are expected to be applied in intelligent actuators,soft robots and other fields.However,traditional responsive hydrogels require direct contact with environmental stimuli(temperature,pH,etc.)to produce response behavior,water and other substances are required as the medium.In addition,the response rate is relatively slow.For example,temperature-sensitive hydrogels usually need more than 10 hours to completely collapse,which limits the application of stimulus-responsive hydrogels.A novel composite hydrogel consisting of graphene oxide(GO)sheet,poly(N-isopropyl acrylamide)(PNIPAM)microsphere and PNIPAM chain was designed and synthesized.By controlling the polymerization time,PNIPAM microgels loaded with double bonds with different particle sizes were obtained,which were used as part of the cross-linking point to polymerize with N-isopropyl acrylamide(NIPAM)to improve the hydrogel response rate.GO was added into the hydrogel system as nano-filler for photothermal transformation.The composite hydrogels prepared by this method are sensitive to both temperature and near-infrared light and have a fast response rate.Then GO was modified and chemically reduced to further improve the mechanical properties and response properties of the composite hydrogel.In this paper,the effects of GO amount,microgel synthesis time,NIPAM concentration and other conditions on the photosensitivity,temperature sensitivity and mechanical properties of hydrogels,as well as the effects of GO chemical modification and chemical reduction on the properties of hydrogels were investigated.Differential scanning calorimetry,scanning electron microscopy,infrared spectroscopy,Raman spectroscopy and other characterization methods were used to analyze the effects of preparation conditions and the hydrogels components on the structure and properties of hydrogels.Compared with traditional PNIPAM hydrogels,the composite hydrogels can respond to both near-infrared light and temperature,and have a better response rate and degree.In this paper,a kind of light-controlled microfluidic valve for non-contact control is designed by using the near-infrared light response behavior of the composite hydrogel,and the bending behavior of the hydrogel strip is realized by using the difference of the hydrogel response rate.