【作者】 董巍；

【导师】 许湧深；

【作者基本信息】 天津大学 ， 材料学， 2007， 硕士

【摘要】 在水介质中,以过硫酸钾(KPS)引发丙烯酸乙酯(EA)和功能性单体甲基丙烯酸二甲氨基乙酯(DM)在羟丙基甲基纤维素(HPMC)上的乳液接枝共聚合,反应经历了分散、成核、增长及聚合后期四个阶段。考察了功能单体DM对引发剂KPS分解行为的影响,结果表明,功能单体DM与KPS可形成氧化还原引发体系,大大加速了其分解反应,但是仍然符合一级反应规律。文中对接枝共聚合的影响因素进行了考察,结果表明,在恒定的反应时间内,增加引发剂KPS的浓度可以显著提高单体转化率,但是KPS浓度过高会导致接枝参数的下降;提高反应温度同样可以增加单体转化率,但过高的反应温度不利于体系的稳定;增加单体与底物HPMC的比例,可以提高单体转化率和接枝率,并降低接枝效率;增加混合单体中DM单体的比例,会加重链转移不利于接枝反应的进行,降低接枝率和接枝效率。在实际操作时,应根据需要选择合适的反应条件与恰当的共聚组成。采用各种分析手段对接枝产物的结构和性能进行了表征。IR分析证实聚合反应中存在化学接枝。TEM可以清晰观察到粒度均一,分散较好的核壳型乳胶粒。SEM和DSC测试表明,随着单体接枝效率的增加,产物的相容性提高。与未接枝的纤维素相比,接枝产物的柔韧性和抗吸湿性提高,而热稳定性却略有下降。DM胺基功能单体的引入赋予接枝产物的pH敏感性,使接枝产物的游离膜可以在模拟人工胃液中崩解甚至溶解,而在中性水中不溶,可作为药物载体实现缓释给药。以此接枝产物的乳液产品为包衣液对模型药物进行包衣,研究了其在药物缓释上的应用。初步探索其缓释原理和释药动力学,药物释放过程主要遵循Fick扩散定律,释药速率符合一级方程或是经典的Higuchi方程。将以上亚微米级乳液进行酸化处理,可以得到纳米胶乳。初步研究了纳米胶乳的形成机理和稳定条件,结果表明,共聚物中的DM结构单元在酸性介质中生成季铵盐,使它定位于乳胶粒表面,该离子化层是纳米胶乳形成的关键因素。并考察了DM用量和HCl用量对酸化前后乳胶粒直径的影响。更多还原

【Abstract】 The graft copolymer of ethyl acrylate (EA) and dimethylaminoethyl methacrylate (DM) onto hydroxypropyl methylcellulose (HPMC) was synthesized in the presence of potassium persulfate (KPS) as initiator in aqueous medium. The graft copolymerization underwent four stages of kinetics including dispersion, particle-formation, growth and final stage. The influence of functional monomer DM to the decomposition behavior of initiator was evaluated. The results indicate DM and KPS can form an oxidation reduction system, consequently initiator decomposition reaction is accelerated greatly, but it still conforms to linear equation. The effects of various reaction conditions on grafting parameters were investigated in detail, such as concentration of initiator, reaction temperature, monomers amount, and monomer composition. Increasing initiator concentration and reaction temperature both benefit the graft copolymerization, but it will be instability when they were exorbitant. The true grafting yield (GT) increased and the monomer graft efficiency (GE) decrease with increasing the comonomer fraction. Increasing DM fraction embarrass the graft copolymerization, resulting in the declining GT and GE. Apropos reaction conditions and right monomer component should be considered cautiously in actual situation.Evidence of grafting was affirmed by use of FTIR. The particles with core-shell were observed through TEM. SEM and DSC thermographs imply that increasing GE can improve compatibility of HPMC with homopolymers. The tensile experiments demonstrate the graft chains reduce the intensity but enhance the flexibility of cellulose. The hydrophobic graft chains improve the moisture absorbency property. Introducing DM unit with tertiary amino groups confer a novel pH-sensitive property onto the graft copolymers and extend its application in the drug delivery system.Tablets of theophylline as the model drug were film-coated with the submicron-sized latex to study the application of the polymeric latex in drug delivery system. The effects of monomer amount and monomer composition on the drug sustained-release were evaluated respectively. Drug release is mainly controlled by diffusion and the best-fit release kinetics is achieved with first-order or Higuchi equation.Nanosized copolymer latex of HPMC-EA-DM was prepared by acidifying the submicron-sized latex particles. The dimethylamino group-containing particles ionized into quaternary ammonium and swelled with water in acidic conditions. The neutralized degree of DM unit is critical for the preparation of nanosized particles. The effects on the diameter of the latex particles of different conditions, such as concentration of DM and ratio of HCl to DM for acidification were studied respectively.更多还原