【作者】 徐世美；

【导师】 杨锦宗； 张淑芬；

【作者基本信息】 大连理工大学 ， 化学工程与技术， 2008， 博士

【摘要】 有机/无机纳米复合水凝胶兼有无机材料的强度、热稳定性以及有机聚合物的功能性,涉及有机、无机、材料、高分子等交叉学科,是目前水凝胶领域的研究热点。与有机水凝胶相比,有机/无机纳米复合水凝胶能够改善凝胶的吸水、耐盐及强度等综合性能,可应用于医药、卫生、农林、园艺等领域。代替以阳离子表面活性剂为插层剂,本文选用阳离子聚丙烯酰胺为插层剂,在远大于膨润土阳离子交换容量的用量下,通过单体插层聚合法和聚合物溶液直接插层法,分别制备了阳离子聚丙烯酰胺/膨润土纳米复合物,之后进行淀粉接枝丙烯酸的交联聚合反应得到互穿和半互穿结构两种两性纳米插层复合水凝胶。所得凝胶具有良好的溶胀能力与凝胶强度。在99.6%高含水量下,单体插层聚合法制备的凝胶强度是聚合物溶液直接插层法的2倍,可达28.9 KPa;最大溶胀倍率也优于后者,可达1010 g/g。实验分别就两种合成方法下不同反应条件,包括引发剂用量、交联剂用量、丙烯酸用量和粘土含量等因素,对所形成凝胶的溶胀性能以及聚合体系温度的影响进行了全面考察,并通过FTIR、XRD、TEM等分析手段对产品结构和插层效果进行了表征,同时通过凯式定氮、分子量等测定对样品进行了定量表征,从而很好地解释了两性纳米插层复合水凝胶具有优良性能的原因,以及两种不同合成方法下水凝胶表现出的性能差异。为进一步提高两性纳米插层复合水凝胶的溶胀速率,本文通过加入尿素作为制孔剂,利用其水溶液在高温下分解产生CO₂和NH₃的原理制孔,避免了常用碳酸盐类制孔剂对pH、孔发生时间和凝胶化时间等条件的特殊要求,从而使制孔变得简单易行,且吸液性能和吸液速率均得到明显改善,其中溶胀倍率较未加尿素（加热）时所得凝胶提高了约1倍,而吸液速率提高了40倍左右。实验考察了尿素用量、加热速率、不同洗涤方式和干燥方式等因素对溶胀性能的影响,并对吸液动力学进行了探讨。基于阳离子聚电解质对膨润土的良好插层以及作为最终水凝胶的半互穿组分对溶胀和强度的贡献,本文又选用水溶性好、电荷密度高,合成方法简单的聚二甲基二烯丙基氯化铵作为插层剂,通过聚合物溶液插层法,制备了剥离型的聚二甲基二烯丙基氯化铵/膨润土纳米复合物。实验详细考察了不同聚合温度、引发剂用量和单体浓度等聚合条件对聚二甲基二烯丙基氯化铵分子量及插层效果的影响,并通过FTIR、XRD、TEM等分析手段对产品结构和插层效果进行了表征。在制得剥离复合物基础上,通过淀粉接枝丙烯酸的交联聚合反应得到半互穿结构两性纳米复合水凝胶。就不同反应条件,包括引发剂用量、交联剂用量、反应温度、丙烯酸用量和聚二甲基二烯丙基氯化铵用量等因素,对所形成凝胶的溶胀性能的影响进行了考察。并测试了两性纳米复合水凝胶对pH、盐种类和盐浓度的响应性和凝胶强度。结果证明,两性半互穿和纳米复合结构提高了水凝胶的溶胀性能与机械强度。与传统水凝胶相比,其凝胶强度提高了1倍以上,在99.2%的含水量下,可达28.2 KPa,且在广泛的pH范围内仍能保持较高的溶胀倍率。采用相似的结构设计思想,本文选用无机硅来构建聚丙烯酸/SiO₂纳米杂化复合水凝胶。分别以水溶性的3-氨丙基三乙氧基硅烷和硅酸钠为硅源,用sol-gel方法合成无机硅网络,同时进行丙烯酸的交联聚合反应构建有机网络,最终得到双网络结构聚丙烯酸/二氧化硅纳米杂化复合水凝胶。用HF处理凝胶样品,并与处理前凝胶对比,通过TEM观察SiO₂在凝胶中的分散形式,取得了较好的效果。结果表明:以3-氨丙基三乙氧基硅烷为硅源形成的SiO₂粒子约为100 nm左右,分散在有机聚合物网络中,凝胶表现出良好的压缩强度和溶胀能力,在99.1%含水量下,凝胶强度可达59.0 KPa,最大溶胀倍率为1084.7 g/g,且溶胀后的凝胶仍具有一定的拉伸性;而以硅酸钠为硅源得到的纳米杂化复合水凝胶呈现以SiO₂为核,交联聚丙烯酸为壳的核壳式结构.凝胶最大溶胀倍率可达1252.7 g/g。凝胶的硬度很好,且耐盐性突出:当含水量为99.1%时,凝胶强度达45.6 KPa。当NaCl溶液浓度由0.9%提高到1.8%时,凝胶溶胀能力下降幅度在10%以内,而传统有机凝胶则下降了25%。更多还原

【Abstract】 Organic/inorganic nanocomposite hydrogels, as a new type of hydrogel, have both stability of inorganic compounds and the functionality of organic compounds. The research on nanocomposite hydrogel covers organic chemistry, inorganic chemistry, material, polymer and other interdisciplinary subjects, and becomes the intensive topic. Compared with conventional organic hydrogels, organic/inorganic nanocomposite hydrogels can improve the swelling, salt tolerance and mechanical strength of hydrogels, so they are expected to have a application in the fields of medicine, sanitary materials, agriculture, forestry and etc.Instead of cationic surfactant as an intercalating agent, we choose cationic polyacrylamide to intercalate into bentonite forming cation polyacrylamide/bentonite nanocomposite under a large dosage much more than cationic exchange capacity of bentonite through both monomer intercalative polymerization and polymer solution intercalation. Then amphoteric nanocomposite hydrogels with interpenetrating polymer network （IPN） or semi-IPN structure are obtained by subsequent crosslinking graft polymerization of acrylic acid onto starch. The resulting hydrogels show good swelling capacity and mechanical strength. The strength of hydrogel prepared by monomer intercalative polymerization is 2 times of the one by polymer solution intercalation, and reaches 28.9 KPa under a high water content of 99.6%, while the maximum swelling is achieved at 1010 g/g. Some synthesis conditions, including initiator amount, crosslinker amount, content of acrylic acid, bentonite content, and etc, are investigated with respect to the swelling capacity and temperature in the polymerization system. The chemical composition and structure are observed by FTIR, XRD and TEM while a quantitative analysis is given by Kjeldahl method and molecular weight measurement. This gives a good explanation for the swelling behaviors, as well as the difference on the swelling and compressive stress of amphoteric nanocomposite hydrogels by two methods. Urea is used as pore producer to improve the swelling speed of nanocomposite hydrogels instead of traditional carbonate. A porous hydrogel can be produced by decomposition of urea solution into CO₂ and NH₃ at high temperature. As a result, it avoids the special demands for the pH of solution, pore-producing time and gelation time when the carbonate is used as a pore producer, so the process becomes easily feasible. In addition, the swelling capacity and swelling speed are obviously improved. The swelling increases by one time while the swelling speed increases by about 40 times compared with the nonporous hydrogels. Some factors, such as urea amount, heating velocity, washing style and dry method are studied in termed of the swelling capacity. The swelling kinetic is also discussed.Based on satisfactory intercalation of cationic polyelectrolyte into bentonite interlayers and contribution to the good swelling and hydrogel strength, polydiallyldimethylammonium chloride is chosen as another intercalating agent due to satisfactory hydrophility, high charge density and easy synthesis method. Polydiallyldimethylammonium chloride/bentonite nanocomposites are prepared by polymer intercalation. Polymerization conditions are investigated, including polymerization temperature, initiator dose and monomer concentration in respect to the molecular weight and intercalation. FTIR, XRD and TEM are used to characterize the chemical structure and intercalation. Based on the successful exfoliation, amphoteric nanocomposite hydrogels are formed by crosslinking polymerization of acrylic acid onto starch. Some synthesis conditions, including initiator amount, crosslinker amount, polymerization temperature, content of acrylic acid, and content of polydiallyldimethylammonium chloride, are investigated in terms of the swelling capacity. In addition, pH and salt sensitivity, as well as the hydrogel strength of amphoteric nanocomposit hydrogel are measured. The results confirm that amphoteric IPN structure and nanocomposite make a big contribution to the swelling capacity and mechanical strength. The hydrogel strength increases by one time more than the traditional hydrogels and reaches 28.2 KPa under a water content of 99.2%. In addition, the high swelling can be kept in a wide pH range.Inorganic silica is used to fabricate organic/inorganic hybrid hydrogels adopting the similar design above. Silica network is obtained by using the soluble 3-aminopropyltriethoxysilane and sodium silicate as silica precursor through sol-gel technology, while organic polymer network is formed by the crosslinking polymerization of acrylic acid. As a result, the polyacrylic acid/silica nanocomposite hydrogel are formed with double network structure. The hydrogel is treated by HF treatment, and then the distribution of SiO₂ is observed by TEM. The results show SiO₂ particles are distributed in the polymer network in a size of about 100 ran when 3-aminopropyltriethoxysilane is used. The hydrogel exhibits good compressive stress and high swelling capacity. The hydrogel strength reaches 59.0 KPa under a water content of 99.1% and the maximum swelling is 1084.7 g/g, The hydrogel is stretchy even in the fully swollen state. Differently, a core-shell nanocomposite hydrogel with PAA outer shell and SiO₂ inner core is formed when sodium silicate is used. The resulting nanocomposite hydrogel shows distinguished salt tolerance and high hardness. The hydrogel strength reaches 45.6 KPa when the water content is 99.1%. The swelling shows a decrease of 10% below, while the traditional organic hydrogels show a decrease of 25% when the concentration of NaCl solution increases from 0.9% to 1.8%.更多还原