水在凝胶中的存在状态及其对凝胶力学性能的影响

以偶氮二异丁腈为引发剂，通过化学引发聚合合成甲基丙烯酸β-羟乙酯（HEMA）/N-乙烯基吡咯烷酮（NVP）二元共聚物和HEMA /NVP /甲基丙烯酸甲酯（或甲基丙烯酸丁酯）三元共聚物水凝胶，通过示差扫描量热法（DSC）结合热重法（TG）研究了不同单体配比的共聚物水凝胶中水的状态，证明了凝胶中存在3种不同状态的水：非冻结结合水、可冻结结合水和可冻结自由水.结果发现可冻结水的含量主要由NVP含量所决定，NVP单元基本不能键合水，而非冻结水的含量主要受HEMA含量和疏水性单体甲基丙烯酸酯含量影响.疏水性单体的引入使材料的力学强度提高，对凝胶体系具有增塑作用的是非冻结水而不是可冻结的结合水和自由水.

Influence of different states of water in hydrogels on tensile properties

Hydrogel materials were synthesized by radical copolymerization of 2-hydroxyethyl methacrylate (HEMA)、N-vinylpyrrolidone (NVP) and n-butyl methacrylate(BMA)/methyl methacrylate(MMA), with azobisisobutyronitrile (AIBN) as an initiator.The different states of water in swelling hydrogels were studied by means of differential scanning calorimetry (DSC) combined with thermogravimetry (TG).It was found that water in polymer existed in three states:freezing free water, freezing bond water and non-freezing bond water. DSC and TG data show that the content of freezing water in hydrogel increased with the growth of NVP percentage, and the non-freezing water in hydrogel increased with the growth of HEMA and n-butyl methacrylate(BMA)/methyl methacrylate(MMA) percentages.The tensile properties of the material increased with adding the hydrophobic monomers. The plasticization of the material was affected by the non-freezing water in hydrogel rather than by the freezing water.