Research On Respomsive Smart Soft Materials And Devices

In recent years,smart soft materials and their devices have been developed and received extensive attention,among which smart hydrogels play a significant part.Soft materials can respond to external stimuli(such as light,electricity,magnetic field,temperature,p H,etc.),resulting in changes of their colors and shapes.Reprogrammable,controllably deformable smart hydrogels is promising for future wearable devices,soft robotics,and biomimetic devices.However,the singleness of programming and the complexity of the hydrogel structure limit further applications of smart hydrogels.In order to solve the above problems and realize the convenient preparation and reprogramming deformation,this paper mainly includes the following aspects:1)By using thermal sensitive N-isopropylacrylamide(NIPAM)as monomer,clay(Laponite RDS)as physical crosslinking agent,(2-(acryloyloxy)ethyl)trimethylammonium chloride(DMAEA-Q)as cationic additive,ammonium persulfate(APS)and N,N,N’,N’-tetramethylethylenediamine(TEMED)as the redox initiating system,a hydrogel can be prepared by means of radical polymerization.After being immersed it in ammonium molybdate(Mo7)solution,a hydrogel(R7Q7)with photochromic function can be obtained.The photosensitive unit Mo7 endows the hydrogel with color-changing feature under UV irradiation.Different photomasks are used to obtain gels with different blue patterns,which can then be erased in air and written repeatedly using other patterns.Due to the temperature-sensitive properties of PNIPAM,R7Q7 with various design patterns can exhibit reprogrammable deformations under NIR laser.2)The R7Q7 hydrogel was treated with a mixed solution of Mo7 and N-methylol acrylamide.After UV irradiation for 30 s,the degree of discoloration of the hydrogel tends to be saturated.The test results were compared with that treated with Mo7 solution.It can be found that the speed of discoloration is significantly quicker,and the absorption value at700 nm reaches 1.406 after UV irradiation for 5 s,far exceeding the 0.13 of UV irradiation for 120 s after immersion in Mo7 solution.This greatly improves the UV light response rate of the prepared gel,and realizes functions such as photo-printing and photo-writing.3)The R7Q7 hydrogel is treated with the mixed solution of Mo7 and malonic acid.After UV irradiation for 30 s,the degree of discoloration of the hydrogel tends to be saturated.When comparing the test results with the that treated with Mo7 solution,it can be found that,the discoloration speed is significantly increasing.At the same time,the gel treated by this method can maintain a fixed shape for a certain period of time,which is potential in the field of shape memory devices.4)By introducing reduced graphene oxide into R7Q7,the nearinfrared response performance of the hydrogel can be greatly improved,while the UV photochromic performance is retained.Through the combination of ultraviolet light photomask and near-infrared light irradiation,the effect of programmable deformation can still be achieved on the composite gel that appears black in appearance.