Functionalization And Structural Study Of Strong PH Responsive Polyelectrolyte Hydrogels Containing Hydrophobic Components

Polyelectrolyte hydrogels form the network structure through the electrostatic interaction.They have various properties such as controllable mechanical properties,self-healing and stimulation response,and have a promising application in many fields like soft actuation,controllable drug delivery and so on.However,at present,the strength of p H responsive polyelectrolyte hydrogel is low,and its stability in salt solution is poor,which greatly limit its application.To improve the strength and stability of hydrogels,we prepared the polyampholyte hydrogel(PA hydrogel)and polyion complex hydrogel(PIC hydrogel)with electrolyte monomers containing hydrophobic groups.In this way,the mechanical properties and the stability in salt solutions were improved on the premise of maintaining the function of polyelectrolyte hydrogel,which expanded the application range of hydrogels.The main contents are as follows:1.PA hydrogel was obtained by copolymerization of strong anionic monomer sodium pstyrenesulfonate(NaSS) and hydrophobic weak cationic monomer 2-(diethylamino)ethyl methacrylate(DEAEMA)in acidic environment.The hydrogel showed p H responsive shape memory behavior and maintained high mechanical strength when immersing in acid and alkali solution alternately.Moreover,the hydrogel had the unique spontaneous shape changing behavior because of the non-uniform swelling of the hydrogel at the non-equilibrium state.It provided an ideal material for the sustainable spontaneous flexible actuator.2.The hydrophobic monomer DEAEMA was dissolved in strong acidic poly(styrene sulfonic acid)(PSSA)solution and polymerized in the presence of counterions to obtain strong PIC hydrogel.Compared with the PA hydrogel mentioned above,the monomer composition of PIC hydrogel was the same,but the mechanical properties were greatly improved.the PIC hydrogel showed p H responsive shape memory and unique spontaneous shape changing behavior as well,and showed excellent mechanical properties even in high concentration Na Cl solution because of the hydrophobic interaction.In addition,a p H responsive bidirectional flexible actuator were prepared by combining PIC hydrogel with polyacrylic acid hydrogel,and the hydrogel showed information encryption capability by controlling water content.These capabilities greatly expanded the application of polyelectrolyte hydrogel.3.The mechanical properties and p H responsive behavior of a series of PIC hydrogels prepared by different hydrophobic monomers were studied.We proved that the network structure of PIC hydrogel including crosslinking through electrostatic interaction and hydrophobic aggregation of polymer chains,which improved the stability of the hydrogel network.PIC hydrogels formed by monomers with different hydrophobicity all showed p H responsive behavior,the change of hydrophobicity would affect the strength and deformation ability of PIC hydrogel,thus affecting the ability of shape memory and spontaneous shape changing.Therefore,the hydrogel properties could be controlled by adjusting the hydrophobicity of hydrogel,and design the intelligent hydrogels combined with various capabilities.