Preparation And Functional Regulation Of Hydrogels Based On Physical Interactions Crosslinking

Physical interactions can be used to give hydrogels a range of functions such as shape memory,actuation,adhesion and so on.However,many issues exist.The hydrogel actuators have only single actuating mode.The time needed for shape memory of hydrogels is long and precision and controllability of defomation is low.There are few hydrogels that can be used for adhension under water and oil,and the adhesion strength is low.In order to solve the problems,some functional hydrogels were prepared based on physical interaction crosslinking in this work,such as combined hydrogel actuator,ultra-fast and gradient-controlled deformable shape memory hydrogel,controlled adhesive hydrogel under water and oil.The main contents and results are as follows:1.Through the reasonable design of multi-ioint and combined actions,the combinational hydrogel-xerogel actuators were prepared.They can change the actuating direction,not just restricted to one direction of motion.The actuators are designed after the copolymerization with N,N-dimethylacrylamide（DMAA）,graphene oxide（GO）and hectorite clay.They can achieve complex actions of turning and lifting under sequential NIR irradiation to carry an object up-and downwards and round obstacles,or to transfer an object to a target position.2.Shape memory gelatin-tannic acid（GTA）hydrogel with ultra-fast,body-temperature responsive and programmable function was prepared by soaking gelatin hydrogel in tannic acid（TA）solution.Its shape can be fixed within 1 s at room temperature and recover to its original shape within 1 s at 37℃.By controlling the temperature of the recovery process,the hydrogel can be deformed in a gradient controlled way,which can be used to design a logic switch array for temperature control.3.GTA hydrogels also exhibit excellent adhesion properties,and its adhesive strength in air is up to 450 k Pa.But after heat treatment,it can be reduced to 40 k Pa.The adhesive strength is 35 k Pa in 27℃water,while it will be reduced to 8 k Pa in 7℃water.These shows that the GTA hydrogel has excellent controllable adhesion properties.What’s more,it not only in water,salt solution and even in oil have a good adhesion ability.It can pull objects to move in these liquid environments.4.The double bonds were connected to TA to act as a cross-linker and copolymerized with acrylamide（AM）to prepare a hydrogel.The hydrogel not only has the multi-ion responsive shape memory function and self-recovery ability,but also shows interesting self-driven behavior and universality of adhesion.The hydrogel soaking in Fe³⁺solution showed excellent electrical conductivity,and the wearable hydrogel sensor prepared by it could be used to monitor human activities,which provided a potential possibility for the application of conductive hydrogels in intelligent wearable devices.5.Through introducing two components with completely opposite responses to temperature,the hydrogel can be prepared that can achieve shape fixation and recovery in both heating and cooling processes.The permanent network was obtained by copolymerization between AM and N,N’-methylenebisacrylamide（BIS）,and the low-temperature crosslinkable gelatin and high-temperature crosslinkable methylcellulose serve as reverible networks.The hydrogel can not only fix the temporary shape at low temperature and recover at high temperature,but also fix the temporary shape at high temperature and recover at low temperature.It realizes the bidirectional actuating of shape memory,and can be used in many kinds of temperature control occasions.