Preparation And Properties Of Wettability Transit Ion Gels Based On Poly (N-isopropylacrylamide)

In recent years,intelligent interface materials that change the physical or chemical properties of their surfaces by external stimuli have attracted considerable research interest.In particular,interface materials that can undergo reversible wettability changes under external stimuli have great application potential in microfluidic devices,oil-water separation,self-cleaning and anti-fog surfaces,and sensors.Among various stimuli,temperature stimuli are favored by scientists from various countries due to their advantages such as easy realization,easy control,simple operation,and environmental protection.Therefore,temperature-stimulated wetting transition materials are currently as the most research-intensive intelligent interface materials.As the most typical temperature-sensitive polymer,due to its reversible phase transition,poly-N-isopropylacrylamide(PNIPAM)has been widely used as a temperature-responsive material in many fields,including as a temperature-sensitive wetting transformation material.However,PNIPAM-based wettability transition materials currently reported have some disadvantages,such as the preparation methods are more complicated,the wettability transition is small,and the mechanism of wettability transition is still unclear.Therefore,in-depth research and development of PINPAM-based hydrogel wetting transition materials have important theoretical significance and broad application prospects.Based on the existing problems of PNIPAM-based wetting transition materials,the main research contents of this paper are as follows:(1)Preparation and performance of homogeneous PNIPAM hydrogelPNIPAM hydrogel was prepared by simple radical polymerization using N-isopropylacrylamide(NIPAM)as monomer and N,N-methylenebisacrylamide(MBA)as cross-linker.By adjusting the amount of cross-linking agent in the synthesis process,the effects of the amount of cross-linking agent on hydrogel LSCT,swelling ratio,mechanical properties,spatial structure,and wetting transition were analyzed.The studies indicated that when the molar ratio of the crosslinking agent MBA to NIPAM is 3%,the prepared PNIPAM-03 exhibited good temperature response(LCST ～31.7℃),lower swelling rate(～153%),excellent compressive strength(～132.7k Pa)and maximum wettability transition(OCA from ～154.8°to ～129.6°)(2)The wettability transformation mechanism of PNIPAM hydrogel was studied by Molecular Dynamics simulationAiming at the unclear problem of the wettability transition mechanism of PNIPAM hydrogels at present,we have studied its wettability transition mechanism of synthesized PNIPAM by molecular dynamics simulation method.The simulation results show that before and after the phase transition of the PNIPAM polymer chain,the segment transitions from an extended state to a curled state,and the number of water molecules in the first hydration layer around the polymer decreases from ～349 to ～231.In addition,the dehydration of the PNIPAM chain is mainly due to the change of the hydration layer around the isopropyl group.This simulation result reveals the wettability transition mechanism of the PNIPAM hydrogel surface and provides theoretical guidance for the subsequent experiments.(3)Preparation and properties of temperature-responsive super-wetting transition organohydrogels based on PNIPAMA temperature-responsive super-wetting transition organic hydrogel(SHG)was prepared by in-situ polymerization using NIPAM as a monomer and reactive polysiloxane nanogel(RPN)as a crosslinker.Studies have shown that the prepared SHG-03 has excellent super-wetting conversion characteristics.Specifically,at low temperatures(20℃),the material exhibits super-oleophobic/ under-hydrophilic(OCA ～151.5°,WCA ～0°).And at high temperature(45℃),it exhibits lipophilic / superhydrophobicity(OCA ～54.5°,WCA ～156.9°).After 10 heating and cooling cycles,the surface of the material is kept at a low-temperature under-water superoleophobic and high-temperature under-oil superhydrophobic.In addition,the coated glass fiber cloth displays controllable oil-water separation function,and the oil-water separation efficiency beyond 98%,which has a wide application prospect in the field of controllable oil-water separation.