【作者】 邵巧兰；

【导师】 邱高； 鲁希华；

【作者基本信息】 东华大学 ， 材料物理与化学， 2012， 硕士

【摘要】 智能水凝胶具有非常独特的刺激响应性,被广泛应用于药物控制释放、生物物质分离、化学传感器等各个领域,而具有温度响应性、pH响应性和pH/温度双重响应性的水凝胶是应用最为广泛、研究者最感兴趣的智能水凝胶。聚N-异丙基丙烯酰胺是最常用的温敏性高分子,它的低临界溶解温度(lower critical solution temperature, LCST)为32℃；聚甲基丙烯酸是一种具有pH响应性的水溶性高分子。本文首先采用无皂乳液聚合的方法,以天然高分子羟丙基纤维素为模板,合成了具有pH敏感性的PMAA纳米水凝胶,再以PMAA纳米水凝胶为模板,制备了以PMAA纳米水凝胶为核层,PNIPAM为壳层的具有核壳结构的水凝胶,论文主要取得了以下研究成果：(1)研究了不同MAA浓度对HPC溶液和PNIPAM纳米水凝胶的相转变温度的影响。紫外可见分光光度计,测定了不同MAA浓度时HPC溶液浊度的变化。在HPC水溶液中加入少量MAA后,HPC的相转变温度发生了很大程度的降低,并且随着MAA浓度的增加而下降。DLS测定了MAA对PNIPAM纳米水凝胶相转变温度的影响,结果表明弱酸性单体MAA的加入,会影响PNIPAM纳米水凝胶的体积相转变温度,并随着MAA浓度的增加,PNIPAM纳米水凝胶的相转变温度降低。(2)以MAA为单体,采用水相无皂乳液聚合的方法,避免了传统反相微乳液聚合体系中含有大量难以清除的有机溶剂和乳化剂,在不同的温度、HPC浓度、MAA浓度和BIS浓度下,制备了一系列PMAA纳米水凝胶。制备的PMAA纳米水凝胶的粒径从100 nm到240 nm不等,分散性也不等。结果发现随着HPC浓度、BIS浓度的增加,PMAA纳米水凝胶的粒径减小,而随着单体MAA浓度的增加,PMAA纳米水凝胶的粒径增加。综合以上结果,温度为24℃,HPC浓度为0.20 wt%, MAA单体浓度为0.30 wt%, BIS浓度为0.10 wt%的条件下,制备的PMAA纳米水凝胶的粒径是149.8 nm,多分散指数是0.119,分散性能良好。利用这一条件下合成的PMAA纳米水凝胶作为下一步合成核壳结构水凝胶的核层。在AFM以及TEM下观察了水凝胶的表面形貌,采用FTIR对其结构进行了表征,DLS以及紫外可见分光光度计对PMAA纳米水凝胶的环境敏感性进行了表征,合成的水凝胶具有良好的pH敏感性。(3)以PMAA纳米水凝胶为模板,以N-异丙基丙烯酰胺为单体,制备了具有pH和温度双重敏感性的具有核壳结构的PMAA/PNIPAM水凝胶。在不同的NIPAM单体浓度和BIS浓度下,制备了一系列的粒径在200 nm到658.3 nm的PMAA/PNIPAM水凝胶。结果表明随着NIPAM单体浓度的增加,PMAA/PNIPAM纳米水凝胶的粒径增加,而随着交联剂含量的增加,粒径降低。当BIS的质量分数为0.267 wt%,1.50g (1 wt%) NIPAM,0.30g (0.267 wt%)APS引发剂和0.10g(0.1 wt%)加速剂TMEDA时,合成的PMAA/PNIPAM水凝胶的粒径较小为338.8 nm,多分散指数为0.164,分散性较好。DLS测试了纳米水凝胶粒径的变化,FTIR和NMR表征了纳米水凝胶的结构特点。AFM对形貌进行了表征,TEM表征了核壳结构的形成,紫外可见分光光度计以及DLS的测试表明合成以PMAA纳米水凝胶为核、PNIPAM纳米水凝胶为壳的PMAA/PNIPAM水凝胶,具有良好的pH响应性和温度敏感性。更多还原

【Abstract】 Smart hydrogels comprising environmentally responsive polymers continue to attract attention due to their potential applications in numerous fields, including drug delivery, chemical separations, sensors and catalysis. Perhaps the most widely study class of responsive nanohydrogel are pH-, temperature-, or both responsive hydrogels. Poly(N-isopropylacrylamide) (PNIPAM) is the most representative temperature-responsive poymer. Poly(methacrylic acid) (PMAA) is a pH-respensive water soluble polymer. We have successfully synthesized the surfactant-free poly(methacrylic acid) (PMAA) nanogels using a natural polymer hydroxypropylcellulose (HPC) as a template in aqueous solution. Finally, pH- and temperature-sensitive PMAA core/PNIPAM shell nanogels using PMAA nanogels as a template were synthesized in aqueous solution. The main achievements are as follows:(1)Different MAA concentrations affected the phase transition temperature of HPC solution and PNIPAM nanohydrogel. UV-Vis spectrophotometer measured absorbance of HPC solution at different MAA concentrations. After adding a small amount of MAA, the phase transition temperature of HPC decreased quickly. It is noted that an increase in MAA concentration resulted in the decreasing phase transition temperature of the HPC solution.(2) A series of pH-sensitive PMAA nanohydrogels were prepared by surfactant-free emulsion polymerization(SFEP) with different temperatures, HPC concentrations, MAA concentrations, BIS concentrations. The size of the resulting PMAA nanohydrogel ranged from 100 nm and 240nm. An increase in BIS and HPC concentration resulted in a decrease in the particle size. As monomer MAA concentration was increased, the size of the PMAA nanogels became larger. Specifically, As the PMAA nanogels were prepared at 24℃,0.20 wt% HPC,0.30 wt% MAA,0.1 wt% BIS, the size of the nanogels is 149.8 nm and its polydispersion index (PDI) is 0.119. Using the PMAA nanohydrogel as a template, monomer NIPAM in the PMAA nanogel dispersion was polymerized to form PMAA/PNIPAM core/shell nanohydrogel. The morphology of the nanodydrogels was characterized by atomic force microscope (AFM) and transmission electron microscope (TEM). The structure of PMAA nanohydrogels was studied by fourier trandform infrared spectrometer (FTIR). Dynamic light scattering (DLS) and UV-vis spectrophotometer indicate that PMAA nanohydrogels had good pH sensitivity.(3) Smart PMAA core/PNIPAM shell nanohydrogels with pH- and temperature- sensitivity were synthesized by using PMAA nanohydrogels as templet and N-isopropylacrylamide as monomer. The size of the resulting PMAA/PNIPAM nanohydrogels ranged from 200 nm to 658.3 nm were prepared with different NIPAM and BIS concentrations. The results showed that the size of PMAA/PNIPAM nanohydrogels increased with an increasing NIPAM monomer concentration but decreased as increasing crosslinker concentration. The size of PMAA/PNIPAM nanohydrogels synthesized with 0.267wt% BIS,1 wt% NIPAM,0.267 wt% APS initiator and 0.10 wt% accelerator TMEDA is 338.8 nm. The narrow dispersivity of PMAA/PNIPAM nanohydrogels is 0.164. The size variation of PMAA/PNIPAM nanohydrogels was measured by dynamic light scattering (DLS) and inner structure was characterized by fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR). The morphology of PMAA/PNIPAM nanohydrogels was characterized by atomic force microscope (AFM) and the formation of core/shell was characterized by transmission electron microscopy (TEM). Ultraviolet/visible spectrophotometer (UV) and DLS show that PMAA/PNIPAM nanohydrogels have been synthesized in which PMAA nanohydrogels are core and PNIPAM nanohydrogels are shell. PMAA/PNIPAM nanohydrogels demonstrated excellent pH responsiveness and temperature sensitivity.更多还原