【作者】 赵骞；

【导师】 孙建中；

【作者基本信息】 浙江大学 ， 化学工程， 2009， 博士

【摘要】 本文采用一种新型的冰冻聚合法合成了具有多孔结构并能随环境变化迅速发生体积相转变的智能水凝胶,并提出了调节凝胶微观孔结构的新方法。在N-异丙基丙烯酰胺(NIPAAm)冰冻聚合的过程中加入十二烷基二甲基苄基溴化铵(DDBAB),它能与水溶性引发剂过硫酸铵(APS)原位反应生成一种不溶于水的引发剂十二烷基二甲基苄基过硫酸铵(DDBAPS),DDBAPS在水中以数百纳米的团聚体的形式存在,从而形成了一种独特的非均相引发体系,使制备而得的聚N-异丙基丙烯酰胺(PNIPA)水凝胶具有相互联通的大孔结构。这种水凝胶对温度变化能做出超快速的体积相转变。在DDBAB存在的条件下,用二氧六环与水的混合溶剂作为NIPAAm冰冻聚合的溶剂,研究了混合溶剂中不同二氧六环浓度对所得水凝胶宏观与微观形貌的影响,并深入分析了产生这些影响的原因。随着合成所用混合溶剂中二氧六环浓度的增加,原位反应生成的非均相引发剂DDBPAS团聚体尺寸减小,从而使所得非均相凝胶逐渐趋于均相,其微观形貌也由相互联通的多孔结构转变为不相联通的多孔结构。具有不相联通多孔结构的PNIPA水凝胶能用来进行乳液的快速浓缩。制备多孔PNIPA水凝胶时加入PVA,可阻止或减缓原位生成的DDBAPS团聚体的聚并。聚并的速率与团聚体的尺寸可以根据PVA用量的多少进行调控。通过对团聚体尺寸的控制,可以合成一系列具有不同尺寸孔结构的水凝胶。制备了一种新型的多孔性壳聚糖/PNIPA半互穿网络水凝胶,然后通过戊二醛桥键将辣根过氧化物酶(HRP)固定到这种半互穿网络水凝胶上,研究了固定化酶的稳定性,并用其催化了丙烯酰胺的聚合。此外,还提出了一种用热敏性载体固定化酶进行催化反应的新工艺。通过对具有多孔结构的聚丙烯酰胺(PAAm)水凝胶的碱性水解,合成了具有超快速pH响应性与高溶涨率的阴离子PAAm水凝胶。更多还原

【Abstract】 In this study,A novel technique to synthesize macroporous hydrogels with ultra rapid environmental sensitive properties was proposed.Moreover,the porous structures of hydrogels were controlled by several methods.A novel freezing polymerization method of synthesizing macroporous poly(N-isopropylacrylamide)(PNIPA) hydrogels was proposed.Polymerization process was taken place in the presence of dodecyl dimethyl benzyl ammonium bromide(DDBAB).A hydrophobic initiator dodecyl dimethyl benzyl ammonium persulfate(DDBAPS) was proved to be produced in situ by the reaction of DDBAB and the water-soluble initiator ammonium persulfate(APS),and a heterogeneous initiation mechanism was proposed.The resulted poly(N-isopropylacrylamide) (PNIPA) hydrogels were macroporous with large swelling ratios and ultra rapid thermo responce rates.Mixed solvents which were composed of pure water and 1,4-dioxand at various concentrations were used instead of pure water during the novel freezing polymerization process.The aggregate size of the hydrophobic initiator DDBAPS became smaller when the concentration oF 1,4-dioxane increased.The effects of the mixed solvent on morphology,swelling ratio,and thermo response kinetics of the resulted hydrogels were investigated.Moreover,the resulted hydrogels were used for emulsified paraffin concentration.The different separation performance attributed to the different structure of gel matrix.Poly(vinyl alcohol)(PVA) was involved to control the pore size of the hydrogels. Morphology of the resulted hydrogels was studied by both optical microscope and scanning electron microscope(SEM).Moreover,the pore size and its distribution were examined by mercury intrusion porosimetry(MIP) examination.The results indicated that size of the pores decreased with the increase of the amount of added PVA.The mechanism was explained after dynamic light scattering(DLS) measurement of the size of hydrophobic initiator DDBAPS aggregates which were formed in situ in PVA aqueous solutions of various concentrations as the product of the reaction between DDBAB and APS.Thermosensitive hydrogel made up of chitosan/PNIPA semi-interpenetrating network(semi-IPN) was synthesized.Horseradish peroxidase(HRP) was then immobilized on this hydrogel that acted as an enzyme-carrier by glutaraldehyde bridge.Polymerization of acrylamide was initiated by a redox system and was catalyzed by the immobilized enzyme at room temperature.The attention was focused on the properties of the carrier-enzyme systems.The properties of the immobilized enzyme such as enzyme activity,storage stability,and thermo stability were also studied.The immobilized enzyme could be used repeatedly.The macroporous hydrogel would be a suitable enzyme carrier for practical applications in future. Moreover,a novel enzymatic-mediated process using PNIPA hydrogels was proposed.Porous polyacrylamide(PAAm) hydrogels were hydrolyzed under alkaline condition to form anionic PAAm hydrogels with super rapid pH sensitive properties as well as very high swelling ratios.更多还原