Preparation And Properties Of PBA Microsphere Toughened Hydrogel

Hydrogels are a kind of soft materials with a large amount of water.In recent years,they have attracted much attention in various fields.However,the conventional hydrogels showed a poor mechanical property because of the heterogeneous network structure and the lack of energy dissipation mechanisms,limiting the application range of tissue engineering,such as artificial cartilage,tendon and blood vessel.Therefore,exploring the hydrogels with excellent mechanical properties had both theoretical and practical significance.The first part of research contents was based on the structural feature of traditional hydrophobic association hydrogels to improve the mechanical properties of hydrogels by synthesizing and introducing functional macromolecular microspheres?PBA-MMs?.Firstly,the PBA-MMs with different particle sizes and pendent double bonds in their surface were prepared,which butyl acrylate as a main component and dicyclopentyl acrylate as an intermolecular crosslinker by traditional emulsion polymerization method.Then acrylamide?AAm?and hexadecyl methacrylate?HMA?as monomers were crosslinked by PBA-MMs as chemical crosslinking agents and hydrophobic association centers to form PBA-MMs crosslinked poly?acrylamide-co-hexadecyl methacrylate??P?AAm/HMA?-MMs?hydrogels by means of free radical polymerization.The results of tensile measurements indicated that P?AAm/HMA?-MMs hydrogels exhibited dramatic enhancement of fracture stress?0.55 MPa?,fracture strain?5533%?and tearing energy(800 J·m^-2)compared to the original hydrophobic association hydrogels?P?AAm/HMA??.Moreover,the hydrogels also revealed the excellent puncture resistant property.Based on traditional mechanisms of rubber-toughened plastics,it was clear that PBA-MMs could not only prevent the further development of cracks but also be stretched to deform and absorbed a large amount of energy.Therefore,the double functional macromolecular microspheres could effectively toughen and strengthen properties of hydrogels,which would open a new approach to enhance the mechanical properties of hydrogels.In the second investigation,the influences of different initiation systems on the mechanical properties of MMs toughed hydrogels were investigated.The thermal initiator was potassium persulfate and the redox initiators consisted of potassium persulfate and N,N,N?,N?-tetramethylethylenediamine.The hydrogels prepared by the thermal initiation system possessed inhomogeneous and incomplete network structure.The swelling ratio was 45 times to its original size and the tensile strength only achieved 0.77 MPa.However,the internal network structure of the hydrogels obtained by a redox initiation system was homogeneous,and the swelling ratio was only 8 times and the tensile strength can reach1.58 MPa.Moreover,the hydrogels with redox initiators exhibited rapid self-recovery,they could recover to its 90%original dimension rapidly when the external force was unloaded.Therefore,the network structure and the mechanical property of hydrogels were improved effectively using the redox initiation system.