Preparation And Properties Of Physical Crosslinked Hydrogels Based On Hydrophobic Association

As a kind of soft and wet material,hydrogel has attracted wide attention of scholars at home and abroad in the fields of flexible devices,tissue engineering and environmental protection.Due to the lack of effective energy dissipation mechanism,traditional chemical crosslinked hydrogels are prone to form permanent damage under external forces,which severely limits the application of hydrogels.In recent years,some hydrogels with high mechanical strength have been prepared by means of non-covalent physical crosslinking to regulate the crosslinking structure of hydrogels.However,with the increasing application demand of various industries,hydrogels with excellent mechanical properties and functionality has become the focus of many researchers.In this thesis,the main objective is to develop functional hydrogels with excellent mechanical and self-healing properties.Based on reasonable design of hydrogel structure,hydrophobic association hydrogels with super adhesion,3D printable fabricaitonand organic dye absorbency were prepared in turn,providing a new idea for developing high-strength and self-healing hydrogels with practicalvalue.The research contents and conclusions of this paper are depicted as follows:（1）The study of preparation and properties of poly（butyl acrylate-co-ethyl methacrylate）（P（BA-co-HEMA））based hydrogelHydrogel precursors were prepared by free radical polymerization of hydroxyl containing monomer of ethyl methacrylate（HEMA）and hydrophobic monomer of butyl acrylate（BA）under irradiation of ultraviolet light.The mechanical test indicated that the tensile strength,elongation at break,and young’s modulus were 275 KPa,2100%and 170 KPa,respectively.At room temperature,the hydrogel achieved 98%self-repair efficiency within 6 h.In addition,the hydrogel also showed excellent adhesion behaviour with the maximum adhesion strength up to6.3 MPa,and its adhesion strength gradually increased with the extension of drying time under pressure.（2）The study of preparation and properties of poly（methacrylate-co-methyl methacrylate-butyl-co-acrylate）（P（MAA-co-DMA-co-BA））based hydrogelHydrogels were prepared by copolymerization of hydrophobic monomer of butyl acrylate and ampholytic crosslinkers of DMA and MAA,followed by soaking in water.The ampholytic crosslinker supported the crosslinking of hydrogel precursor,and further hydrated to induce hydrophobic association and caused the transformation from hydrogel precursor to hydrogel.The mechanical test showed that the tensile strength,elongation at break,and young’s modulus were 110 KPa,150%,and 127 KPa,respectively.At room temperature,hydrogel achieved 99%self-healing efficiency within 6 h.Due to the strong cross-linking effect of amphoteric ion crosslinking agent,hydrogel precursor can be prepared by 3D printing technology,and this contributed to realize the customized fabrication of hydrogel.（3）The study of preparation and properties of Fe₃O₄@P（MAA-co-DMA-co-BA）nanocomposite hydrogelNanocomposite hydrogels with dual physical cross-linked networks were prepared by introducing Fe₃O₄ nanoparticles into P（MAA-co-DMA-co-BA）based hydrogels.The characterization results showed that there was coordination interaction between Fe₃O₄nanoparticles and polymer chain.The electrostatical interaction together with hydrophobic interaction resulted to a dual physical crosslink network,and this effectively improved the mechanical properties of the hydrogel.In addition,the nanocomposite hydrogel was applied to the wastewater treatment of printing and dyeing industry.The research results showed that the nanocomposite hydrogel could effectively absorb organic dye of bright blue,and the removal rate reached as high as 81.4%under the sampling interval of 5 h.Furthermore,the effect of temperature on the adsorption rate is investigated,and it was found that the best adsorption effect was achieved at 60°C.