【作者】 肖新才；

【导师】 陈文梅； 褚良银；

【作者基本信息】 四川大学 ， 化工过程机械， 2003， 博士

【摘要】 温度感应型凝胶微球作为智能材料系统中的一部分，正受到国际上越来越多研究工作者的关注。温度感应型凝胶微球由于其体积小、温度敏感性高，在许多领域如药物释放、化学分离、化学传感器和催化剂等方面有着诱人的潜在应用前景。尽管迄今人们已在温度感应凝胶微球方面取得了许多研究成果，但还有许多问题尚待解决。例如，在靶向给药系统(targeting drug delivery system，TDDS)中，就要求药物载体——凝胶微球的粒径小，而且要求其具有较好的单分散性。另外，在某些领域，需要随温度变化时，感温凝胶微球的体积变化趋势与现有的基于聚(N-异丙基丙烯酰胺)的感温凝胶微球的体积变化趋势相反(即要求随温度的升高，凝胶微球的体积变大)。因此，本文在基于PNIPAM的小粒径单分散感温性反相凝胶微球的制备及感温特性研究、基于氢键作用的温度感应性正相凝胶微球的研究微球种子的制备、IPN结构凝胶微球的制备及其感温特性、感温性凝胶微球在温敏控制释放过程中的“微泵作用”等方面进行了较为系统地研究，取得了创新性的成果。 聚(N-异丙基丙烯酰胺)(PNIPAM)由于其低临界溶解温度(LCST)较低，对温度感应比较灵敏，一直是反相感温凝胶(Negative thermo-responsive hydrogel)的主要基材。本文采用无皂乳液聚合制备了聚(N-异丙基丙烯酰胺-co-苯乙烯)(Poly(NIPAM-co-St))凝胶微球，得到了表面规则、球形度好、粒径较小、单分散性好的凝胶微球。首次系统地研究了引发剂、搅拌速度、相 摘要比以及反应时间等因素对Poly(NIPAM一co--St)微球的粒径和单分散性的影响。当引发剂量增加时，微球粒径先略有上升而后迅速减小，而单分散性先较好随后变差:随搅拌速度的增加，凝胶微球粒径总是呈下降的趋势，而粒径的单分散性随搅拌速度的提高，先比较好，而后变大，最后又变好;当增加相比量时，微球的粒径增加，单分散性先变差后变好;粒径随反应时间的增加先略减小后略增加，而其一单分散性总体呈逐渐变好的趋势;随聚合反应的进行，首先生成卜异内大红内烯酞胺聚合物，然后苯乙烯进入聚(千异丙基丙烯酞胺)微粒内部生成聚合物，最终形成疏水性核一亲水性壳结构。综合以上的影响因素，进行了优化条件下的制备实验研究，得到了粒径较小、单分散性好的微球。在无皂乳液聚合的基础上，进一步进行了种子聚合，得到了感温膨胀性好的核壳结构的复合凝胶微球。在研究过程中，考虑了龙异丙基丙烯酞胺和苯乙烯单体用量对微球的粒径、单分散性及感温膨胀率的影响。结果表明，当增加第二步反应中/卜异丙基丙烯酞胺用量时，复合微球的粒径增加，单分散性变好，同时微球的感温膨胀特性明显、体积变化率大。在第一步反应中，增加苯乙烯加入量时，核壳结构的微球的粒径呈现上升的趋势，粒径的单分散性先变好后变差;同时，微球的感温膨胀率儿乎不变，即增加苯乙烯量对微球的感温膨胀特性几乎没有多大的影响。 了L:国内外首次x寸IF干L!凝胶微球(l，ositive thermo一responsive miero-spheros)(又称为热胀型凝胶微球)的制备和感温特性进行了探索性的研究，取得了满意的结果。借助互穿聚合物网络(Interpenetrating Polymer Network，简称IPN)的结构、原理和制备方法，来制备聚(丙烯酞胺一co--苯乙烯一c。甲基丙烯酸一J一酉旨)/聚丙烯酸(P。ly(AAM一c、St一coBMA)/PAAC)凝胶微球，并月_研究在两步反应过程中诸多因素对粒径、单分散性以及其感温特性的影响。J尸N结构感温型凝胶微球的两聚合物链通过相互之间形成氢键或破坏氢键来实现微球体积的收缩和膨胀，这是正相凝胶微球产生相变的根本原因。正相凝胶微球的种一子采用两步法制备:第一步采用无皂乳液聚合制备微球种子;第二步采用种子聚合，最后的微球具有疏水性核和亲水性壳结构。当制备含有甲基丙烯酸一丁酚的种子时一，在第二步中应选用适当的溶解度参数的混合溶剂，否则制备的种子球形度不太规则;随甲基丙烯酸丁酷量增加，种子的粒径变大，单 摘要分散性变差，球形度也变差口当丙烯酸服的加入量增加时，种子的粒径增加，lllJ单分散性先减小后增加。随苯乙烯量增加时，种子的粒径增加，而粒径尺寸分布先变窄后变宽;当增加交联剂量时，种子的粒径减小，粒径的单分散性变好。 在制备具有IPN结构的凝胶微球中，第一步制备的种子作为第二步反应的场所，因而凝胶微球和种子具有相近的单分散性。在第二步反应中，丙烯酸(从C)的加入量是一个重要的因素。采用物料均衡参与反应的方法，计算得到丙烯酸的加入量。不同丙烯酸的加入量使凝胶微球的粒径不一样，当制备凝胶微球中酞胺基团和梭基基团的摩尔数相等时，在低温情况下，两聚合物链的酞胺基[J]和狡基基团彼此形成氢键，相互作用，彼此约束，没有多余酞胺基或梭基’。水形成氢键，最终造成凝胶微粒的粒径最小。由于丙烯酞胺量在种子表l佰形成毛发状壳层，不同丙烯酞胺量在种子表面形成毛发的长度不一，这类种r制备的凝?更多还原

【Abstract】 As a part of intellectual material, thermo-sensitive hydrogel microspheres are getting more and more attentions. Because of their small diameters and high sensitivity to temperature, thermo-sensitive hydrogel microspheres can be traced to their potential applications in numerous fields, including drug delivery, chemical separation, chemical sensors, and catalysis, which continue to attract more attention of scientific researchers. Although a lot of achievements have been made on the thermo-sensitive hydrogel microspheres, there are still many problems that need to be solved. For example, in the targeting drug delivery system (TDDS), some cases require small diameter and good monodispersity of microsphere drug carrier. In some fields, positive thermo-sensitive microspheres are preferred to negative ones. That is to say, with increasing environmental temperature, the microspheres volume should become larger. In this study, investigations were systematically carried out on preparation and thermo-sensitive characteristics of positive type and negative type hydrogel microspheres, and some exciting results have been gotten.Poly(A-isopropylacrylamide)(PNIPAM) is a preferable material for the preparation of negative thermo-sensitive hydrogel microspheres, because its lower critical solution temperature(LCST) is low and the responsiveness is fast. Thermo-responsive poly(jV-isopropylacrylamide-co-styrene) (P(NIPAM-co-St)) microspheres were prepared by surfactant-free emulsion polymerization methods in this paper. The prepared microspheres have spherical outer surface, small diameter, and good monodispersity. Effects of initiator dosage, stirring rate, phase ratio and polymerization time on the particle sizes and monodispersity were investigated systematically. Then, microspheres was prepared under optimum conditions. Theresults showed that, with increasing the initiator dosage, the mean diameter of particles increased slightly up to a maximum, and then decreased drastically; meanwhile, the monodispersity of the particles became a little better at first, and then became worse significantly. With increasing the stirring rate, the particle diameter decreased while the monodispersity became worse. When the amount of phase ratio increased, the mean diameter became larger simply, whereas the monodispersity became worse firstly and then became better again. As the polymerization proceeded, the mean diameter of the particles decreased firstly and then increased, and the monodispersity became better gradually. In the reaction, NIPAM rapidly homopolymerized, then St entered into precursor particles and polymerized, finally microspheres with hydrophobic core and hydrophilic shell are obtained. Particle size and monodispersity of the microspheres prepared under the optimum conditions were satisfied. On the base of soap-free emulsion, core-shell microspheres prepared by means of seed polymerization are thermo-sensitive. Effects of NIPAM and St dosage on the particle size and monodispersity were investigated. When increasing NIPAM dosage of the second step, the mean diameter became larger simply, whereas the monodispersity became better, and the thermo-sensitive swelling ratio became larger. When St dosage increased in the first step, the particle size also became larger, whereas the monodispersity became worse firstly and then became better again, and St dosage hardly changed the thermo-sensitive swelling ratio of the microspheres.The preparation and the thermo-sensitive characteristics of positive thermo-sensitive microspheres. or so-called thermo-swelling microspheres, were studied for the first time, and the results were satisfied. By adopting the structure and mechanism of interpenetrating polymer network (IPN), Poly (AAM-co-St-co-BMA) /PAAC IPN microspheres are prepared. Effects of some factors on the particle size, monodispersity and thermo-sensitive characteristics are investigated in processes of two-step reaction. Phase transition of these positive microspheres is based on the hydrogen bond between PAAC chains and更多还原