Adhesive Hydrogels Based On Zwitterion

Hydrogel is a three-dimensional network polymer with high water content.Polymer hydrogels with excellent performances,including toughness,responsiveness,self-healing,and adhesiveness,have great potentials for applications in many fields.Especially,adhesive hydrogels have attracted great research interest in electronic skin,tissue adhesives,drug delivery vehicles,wound dressings,soft robotics,biomedical sensors,wearable devices,and so on.Flexible hydrogels allows it to adhere conformally to the substrate.In addition,Adhesive hydrogels with excellent mechanical properties ensure high and stable performance during applications.Therefore,it is desired to prepare an adhesive hydrogel with high toughness and multifunction.The zwitterionic polymers with th e cationic quaternary ammonium groups and anionic sulfonate groups on the same monomeric unit exhibit neutral net charge,but have high dipole moment,whose special structure endow it with various performances.The interchain dipole-dipole association can be formed between the zwitterionic polymers.Zwitterionic groups can interact with other charged groups or polar.groups by forming ion-dipole or dipole-dipole interactions.Also,zwitterionic groups can promote ion conduction.Therefore,we prepared adhesive hydrogels based on zwitterion,studied the adhesion properties,and explored their biological applications.The main work and corresponding conclusions of this paper are as follows:(1)The transparent zwitterionic nanocomposite hydrogels were prepared by copolymerizing zwitterion SBMA and HEMA with the exfoliated Laponite XLG nanosheets,which have excellent mechanical properties and conformal adhesion.Zwitterionic polymers can form interchain dipole-dipole associations to provide more physical cross-linking interactions.The hydrogel exhibits a high fracture strain up to 2000%,a fracture strength up to 0.27 MPa and a fracture toughness up to 2.45 MJ/m3.In addition,reversible physical interactions endow the hydrogel with a rapid self-healing ability.Hydrogels can adhere to many surfaces,including polyelectrolyte hydrogels,skin,glass,silicone rubber and nitrile rubber.The presence of the zwitterionic group promotes ion conduction in the hydrogels.The combination of these properties enables the hydrogel to act as a strain sensor with high sensitivity(sensitivity = 1.8).The design of tough,adhesive,self-healing and conductive zwitterionic nanocomposite hydrogels as skin strain sensors is expected to be used in practice.(2)Zwitterionic polyelectrolyte hydrogels were prepared by copolymerization of zwitterionics SBMA and ionic monomers AMPS or DAC.The mechanical properties,adhesion properties,adhesion mechanism and antibacterial properties of the hydrogels were investigated.The introduction of ionic monomers disrupts the dipole-dipole interaction between the zwitterionic polymer chains,and the fracture strength of the gel decreases but the fracture strain increases.The adhesion properties of the polyanionic electrolyte hydrogel P15SA and the polycation electrolyte hydrogel P15SD were significantly different.This may be attributed to the difference in surface charge distribution between the polyanion and the polycation gels.By measuring the zeta potential of the hydrogels,it was confirmed that the zeta potentials of P15SA gels increased with the increase of AMPS content,and the zeta potentials of P15SD gels did not change with the increase of DAC content.In addition,the adhesion properties between zwitterionic polyelectrolyte gels and pig skin were studied.It was found that the adhesion force of P15S1.8A0.2 gel to pig skin was the largest,and the gel itself broke when the lap joint was stretched.The P15S1.8A0.2 gel adheres firmly to the surface of the pigskin and is able to withstand the bending and twisting of the pigskin.In addition,the zwitterionic polyelectrolyte gels exhibit good antibacterial properties and is expected to promote wound healing as an antibacterial wound dressing.