【作者】 彭志远；

【导师】 谌凡更；

【作者基本信息】 华南理工大学 ， 制浆造纸工程， 2010， 博士

【摘要】 植物纤维是储量丰富、可再生的天然高分子化合物,具有良好的生物相容性和生物降解性能、无毒性的特点。利用可再生的植物纤维开发生产可降解性的高分子材料,实现植物纤维生物质原料在高分子材料领域对石油原料的有效替代,对于缓解能源危机、保护环境,具有重要意义。本研究用不同的方法制备了多种水凝胶。即,以羟乙基纤维素为原料,分别采用接枝共聚和交联剂交联的方法制备羟乙基纤维素基的水凝胶;以甘蔗渣在多元醇中的液化产物和乙酸木质素为原料分别制备对pH敏感的聚氨酯基水凝胶。甲基丙烯酸羟乙酯单封端的2,4-甲苯二异氰酸酯改性的羟乙基纤维素与N-异丙基丙烯酰胺接枝共聚制备温敏性水凝胶。扫描电镜表明冷冻干燥的凝胶断面具有多孔的结构。DSC分析的结果表明,水凝胶的低临界共溶温度(LCST)随着凝胶中羟乙基纤维素的含量的增加而升高。当羟乙基纤维素与N-异丙基丙烯酰胺的比例分别为1:2,1:3,1:4时,制备的水凝胶的LCST分别在46℃、40℃、36℃附近。当温度高于水凝胶的LCST时,凝胶收缩;当温度低于凝胶的LCST时,凝胶溶胀。水凝胶对药物模型物(亚甲基蓝和甲基橙)表现明显的缓释性能。柠檬酸和羟乙基纤维素的混合溶液通过加热脱水,再加热交联制备羟乙基纤维素水凝胶膜。随柠檬酸用量的增加,羟乙基纤维素水凝胶膜的吸水溶胀率降低,拉伸强度增大,断裂伸长率降低。柠檬酸的用量为羟乙基纤维素的20%制备的水凝胶膜,其吸水溶胀率为5.8,在pH为6.86的缓冲溶液中达溶胀平衡的时间为8h;当膜的溶胀率为0.05~0.10和0.40~0.50时,其拉伸强度分别为1.74MPa和0.13MPa,断裂伸长率分别为24.12%和66.05%。柠檬酸和羟乙基纤维素的混合溶液通过冷冻干燥脱水,再加热交联制备多孔水凝胶。水凝胶的孔道尺寸随水的用量的增加而增大。溶胀实验数据表明,多孔水凝胶具有快速的溶胀速率。水凝胶的多孔结构有利于蛋白质、亚甲基蓝在凝胶内部扩散,从而增加其吸附量。当柠檬酸、羟乙基纤维素和水的质量比为1:5:150时,制备的多孔水凝胶的溶胀率为18.5,在pH为6.86的缓冲溶液中达溶胀平衡的时间为2min,水凝胶对牛血清蛋白和亚甲基蓝的吸附量分别为15.7mg/g和7.63mg/g。异氰酸酯封端的聚氨酯离子聚合物交联乙酸木质素合成pH敏感的木质素-聚氨酯基水凝胶。凝胶的溶胀率随pH的增加而增大。当木质素用量为30%时,水凝胶在pH为6.86的缓冲溶液中的溶胀率最大为3.14。热重分析结果表明向聚氨酯水凝胶中引入木质素,可以提高凝胶的热稳定性。木质素-聚氨酯水凝胶包裹的硫酸铵表现出明显的缓释特征。甘蔗渣在PEG-400和甘油的混合试剂中的液化产物合成的端烯基聚氨酯离子聚合物通过自由基反应合成pH敏感的聚氨酯基水凝胶。聚氨酯离子聚合物通过亲水链段和疏水链段的相互作用形成了具有核-壳结构的乳液,由于液化产物中木质素的疏水作用,增大了聚氨酯离子聚合物的微相分离程度。DSC分析结果表明,含有甘蔗渣液化产物的聚氨酯水凝胶溶胀后,其中的可冻结水全部是自由水。溶胀实验表明,含有甘蔗渣液化产物的聚氨酯水凝胶具有pH和离子敏感性。对铜离子的吸附实验表明,含有甘蔗渣液化产物的聚氨酯水凝胶有望应用于金属离子的分离富集。更多还原

【Abstract】 As one of the most abundant natural polymers, lignocellulosic fiber has attracted much attention due to its unique advantages of biocompatibility, biodegrability and non-toxicity. The conversion of lignocellulosic fiber into a new source of raw materials for preparing degradable polymer materials is of great importance to protect the environment and save the fossil resources. In this work, hydrogels were prepared by graft copolymerization and chemical crosslinking of hydroxyethyl cellulose (HEC), respectively. pH-sensitive polyurethane- based hydrogels were synthesized from acetic acid lignin and the liquefaction products of bagasse in polyhydric alcohols,.An isocyanate-bearing unsaturated monomer (MHTI) was synthesized by the monobloking reaction of 2,4-toluene diisocyanate with 2-hydroxyethyl methacrylate. The temperature-sensitive hydrogels were prepared by the copolymerization of N-isopropylacrylamide (NIPPAm) and modified hydroxyethyl cellulose with MHTI. The results of DSC analysis revealed that the low critical solution temperature (LCST) of hydrogels was enhanced by the introduction of HEC. SEM images suggested that the cross-section of freeze-dried hydrogels was porous. The LCST of the hydrogels prepared with the mass ratio of MHEC/MNIPPAm: 1:2, 1:3, 1:4, was approximately 46℃, 40℃, 36℃respectively. The hydrogels were negatively thenmosensitive, shrank in water above the LCST and swelled in water below the LCST. The data of adsorption and release experiments for the model drug (methylene blue and methyl orange) suggest that the controlled drug release can be achieved.Hydrogels film was prepared from HEC using citric acid as a cross-linker. As the citric acid dosages increase, the swell ratio and elongation of film at break decrease, tensile strength of film increase. When the hydrogel film was prepared with the citric acid amount 20% based on HEC, the swelling ratio of film was 5.8 in pH 6.86 buffer solution and the hydrogels achieved an equilibrium swelling state within 8 h; when the swelling ratio of the film was 0.05-0.1 and 0.4-0.5, tensile strength of film was 1.74MPa and 0.13MPa, elongation of film at break was 24.12% and 66.05%, respectively.Porous hydrogels were prepared from HEC using citric acid as a cross-linker with the pores formed by a freeze-drying technique prior to the cross linking reaction. The pore size increased with the increase of the ratio of water to HEC during the preparation of the hydrogels. The data of the swelling ratio demonstrated a fast swelling property of the hydrogel. The porous structure of the hydrogels was in favor of the adsorption of protein and dye. The results of thermogravimetry demonstrated that the thermal stability of HEC was improved by crosslinking with citric acid. The data of percent weight remaining in buffer solution with different pH indicated that the hydrogels were stable in both weak acid and base media. The porous hydrogel prepared with the mass ratio of citric acid: HEC: water: 1:5:150 achieved equilibrium swelling within 8 h in pH 6.86 buffer solutions, and the equilibrium swelling ratio of the porous hydrogel was 18.5. The adsorption amount of protein and methylene blue to the porous hydrogel was 15.7mg/g and7.63mg/g respectively.Polyurethane hydrogels containing lignin were synthesized from acetic acid lignin by chemical crosslinking with isocyanate (NCO)-terminated polyurethane ionomers (IPUI). The swelling ratio of hydrogels increased with the raise of pH. The hydrogel prepared with the mass ratio of mAAL/mIPUI: 0.3:1 presented maximum swelling ratio (3.14) in pH 6.8 buffer solutions. The results of thermo gravimetric analysis demonstrated that the thermal stability of the hydrogels is improved by the introduction of lignin. The hydrogels were used as coating material for ammonium sulfate and the data of release experiments for ammonium sulfate suggest that the hydrogels can be used as coating materials in slow release fertilizer.Polyurethane hydrogels containing liquefaction products of bagasse were synthesized by emulsion polymerization of polyurethane ionomers. The polyurethane ionomer emulsion was formed by the emulsification caused by the microphase separation between hydrophilic and hydrophobic segments of the chains, and the particles in the emulsion give regular spheric, core-shell structure. The polyurethane ionomer prepared from liquefaction products of bagasse present highly microphase-separated degree owing to the hydrophoblic interaction of the lignin in liquefied bagasse. The data of the swelling ratio showed that the hydrogels were sensitive to pH and ionic strength. The results of DSC analysis revealed that the freezing water in the swollen hydrogels were all free water. The adsorption experiment of the hydrogels for Cu (II) ion suggests that the hydrogels can be used as adsorbent for removal of heavy metal ions from aqueous solutions.更多还原