Preparation,structure And Properties Of Responsive High-strength Hydrogels

Hydrogel is a soft and wet material with three-dimensional polymer network structure.It has potential applications in drug release,artificial organs,flexible devices and tissue engineering,etc due to the good biocompatibility.The responsive hydrogels refer to a type of gels whose properties can change accordingly when the external environment changes.However,the limitations of traditional polymer hydrogels in mechanical properties have severely hindered its application in many fields.Therefore,the preparation of high-strength and responsive hydrogels has become an important research topic.The introduction of ions into the hydrogel network is a simple,and effective strategy to improve the mechanical properties of the gels.In this work,a responsive hydrogel with high strength,conductivity and self-healing was prepared based on this method.The soaking method can greatly improve the mechanical properties of the hydrogel.A series of hydrogels with controllable mechanical properties were successfully prepared by immerse the thermo-initiated P(AA-SMA)hydrogel into Li Cl,Na Cl and KCl three kinds of chloride ion salt solution with the same concentration.The structures and properties of the gel before and after soaking were explored carefully by XRD,IR and Raman,etc.It was found that except for forming coordination with the carboxyl group of acrylic acid,these salts can also promote the formation of long alkyl chain hydrophobic associations,which significantly improves the mechanical properties of the gel.The tensile strength and fracture energy of the KCl aqueous solution treated hydrogels could reach to 2.1 MPa and 19 MJ/m~3,respectively,which are much higher than those of original hydrogels.Furthermore,the prepared hydrogels also have pressure sensitive conductivity,which could be used to detect body movements.In addition to the immersion method,the introduction of synergistic interaction in the hydrogels is a common strategy to improve mechanical properties.Therefore,we combine6-acrylamidohexanoic acid(AACA)and[2-(methacryloyloxy)ethyl]trimethylammonium chloride solution(DMC)monomers in a mixture solution of polyvinyl alcohol(PVA)and borax to prepare high strength and p H responsive hydrogel.Compared with borax cross-linked PVA gel,this hydrogel exhibits better mechanical properties owing to multi-physical interactions like electrostatic interactions,hydrogen bonds etc.Due to the presence of noncovalent interactions the hydrogel exhibits different degrees of self-healing ability in acid and alkali condition at the same time.Furthermore,the conductivity of the hydrogel can be significantly change with slight deformation,which can be used to monitor the body movement like swallow and finger bending.