Study On Controllable Preparation And Mechanical Properties Of Acrylic-Acrylamide Hydrogel

The triple-network hydrogels have different network structures and various types of cross-linking ways,which possess excellent comprehensive properties.Therefore,this type of hydrogels is a soft substance which is expected to be widely applied in the future.Triple-network hydrogels with high strength,self-recovery and good thermal stability were prepared by coexistence of chemical covalent bonds and dynamic reversible bonds.The main contents of this paper are as follows.1.Agar/PAAc/PVA triple-network hydrogels were prepared by one-pot-three-step method.Through the freezing method,the physical network was formed,with hydrogen bond crosslinking between agar molecular chains,and then the chemical crosslinking network was built between acrylic acid?AAc?and chemical crosslinking agent by free radical polymerization.The coexisting Fe³⁺in the system coordinated with the carboxyl groups on the chains of PAAc molecules to construct a physical cross-linking network,CNTs were uniformly dispersed in the hydrogel system and formed a cross-link between the physical crosslink points and the hydrogel molecular chains.After freezing treatment,PVA molecules in hydrogels can enhance the degree of entanglement of molecular chains,forming PVA semi-crystalline region.The tensile strength of the prepared Agar/PAAc-Fe³⁺/PVA/CNTs hydrogel was 1.509 MPa,and the compressive strength reached 3.05 MPa at 80%strain.2.Agar/PAMAAc/PVA triple-network hydrogels were prepared by one-pot-three-step method.Firstly,the agar network was formed by physical crosslinking,and then the chemical crosslinking network was constructed by free radical polymerization of acrylamide?AM?and acrylic acid?AAc?monomers.The prepared Agar/PAMAAc/PVA hydrogels experienced the freezing-thawing cycle to form a physically cross-linked PVA semi-crystalline region.Meanwhile,the coexisting Fe³⁺in the system formed dynamic coordination bonds with carboxyl groups and CNTs also formed hydrogen bonds with hydrogel molecular chains.The Agar/PAMAAc-Fe³⁺/PVA/CNTs hydrogels prepared by this method can achieve the compression strength of 1.01 MPa,1.58 MPa and 8.18 MPa respectively when the strain was 70%,80%and 90%.At the same time,the hydrogels can quickly recover its shape after five consecutive or discontinuous compressions.3.Gelatin/PAMAAc/SA triple-network hydrogels were prepared by one-pot-two-step method.The Gelatin,AM,AAc and SA solutions were mixed thoroughly.During thermal polymerization,AM and AAc were polymerized to form PAMAAc network,and at the same time,Gelatin network and SA network were built.Subsequently,the Gelatin/PAMAAc/SA hydrogels were immersed in Fe³⁺solution and Ca²⁺solution respectively,so that the carboxyl groups on the AAc and SA chains formed a dynamic and reversible physical crosslinking network with metal ions,thus constructing the double coordination crosslinked three network hydrogels.When the strain was 70%,80%and 90%,the compression strength of the triple network hydrogels can reach 1 MPa,3 MPa and 12 MPa respectively.