【作者】 姚远；

【导师】 郭睿威；

【作者基本信息】 天津大学 ， 材料学， 2017， 硕士

【摘要】 光降解嵌段聚合物具有刺激响应特性和自组装能力,在智能材料尤其是药物控释载体等领域有广阔的应用前景。可逆加成-断裂链转移（RAFT）反应为合成复杂结构和功能多样的聚合物提供了有效途径,也使光降解嵌段物结构的控制和降解行为的调控成为可能。在RAFT聚合中,由单体头加成产生的尾型自由基会与RAFT试剂作用生成无效RAFT试剂（DDS）,导致嵌段效率和嵌段反应产物纯度的降低。本文利用梯度洗脱液相色谱技术（GPEC）结合RAFT聚合嵌段衍生手段,对RAFT体系中的这一副反应进行了研究。依据RAFT聚合动力学模型,推导了DDS含量与聚合度、转化率、头加成几率以及RAFT试剂对尾型自由基链转移常数之间的数学关系;以丙烯酸苄基酯（BzA）为例,采用具有特殊UV吸收的N-咔唑基二硫代甲酸苄基酯（BCBD）为RAFT试剂,通过BzA的RAFT聚合产物再与较高极性的丙烯酸甲酯（MA）进行嵌段衍生,经GPEC法分离嵌段衍生物中BzA均聚物与嵌段物,通过紫外吸收、¹H NMR和MS等方法证明了DDS的存在,并定量测定了DDS含量;通过改变PBzA聚合度,测定了BzA的头加成几率为0.14%。基于苯基乙烯基酮（PVK）聚合物的光降解特性,以亲水单体甲基丙烯酸二甲胺基乙酯（DMAEMA）与疏水单体丙烯酸异辛酯（2-EHA）顺序加料法,通过RAFT聚合法制备了双亲性三嵌段聚合物PDMAEMA-PPVK-P（2-EHA）,并探讨了其在光控释药的乳液体系中的应用。对比了PPVK及聚对甲氧基苯基乙烯基酮（PMPVK）的光降解行为,PPVK降解速度略高于PMPVK;以双亲性嵌段物PDMAEMA-P（2-EHA）为乳化剂制备了油酸乙酯为油相的环保型W/O型乳液,探讨了油水比、乳化剂结构与添加量以及内水相pH对乳液稳定性的影响,研究表明油水比为2:1,乳化剂选用PDMAEMA₃₂-P（2-EHA）₁₃₅,添加量为0.03 g/ml且内水相pH=5时,能够制备出稳定性较好的细乳液。随后,利用PDMAEMA-PPVK-P（2-EHA）制备了包载草甘磷的W/O型细乳液,并研究了光降解聚合物类型、光降解段链长以及乳化剂添加量对乳液破乳及药物释放速率的影响,结果表明,药物释放速率和破乳速度随光降解链长的增加而加快,随乳化剂添加量的增加而减慢。这些研究为光敏感乳液及草甘膦药物控释体系的制备提供了指导。更多还原

【Abstract】 Photodegradable block copolymers have the ability to respond to external stimuli and self-assemble in selective solvent and thus have a broad application prospect in smart materials,especially in controlled release drug delivery system.The Reversible Addition-Fragmentation Chain Transfer polymerization(RAFT)offers approaches to synthesize polymers with complex structure and multiple function,and make it possible to controll the structure and photodegradation behaviors of photodegradable polymers.In RAFT polymerization,tail-type radicals produced by head addition of monomers will react with RAFT agents to produce non-active RAFT agents(DDS),leading to impurity and the decrease of block efficiency.In this article,gradient polymer elution chromatography(GPEC)and RAFT block chain extension reaction were combined to investigate this side reaction in the RAFT system of acrylate.The mathematical relationship between the content of DDS and polymerization parameters,like the incidence of head addition,degree of polymerization,conversion and chain transfer constant of RAFT agents to tail-type radicals,was deduced based on the kinetic model of RAFT polymerization.The benzyl N-carbazolecarbodithioate(BCBD),which has specific UV absorption,was chosen as RAFT agent to mediate the RAFT polymerization of benzyl acrylate(BzA),and the PBzA-BCBD was chain-extended with methyl acrylate(MA).The homopolymers were separated from block copolymers by GPEC,and the existence and content of DDS was determined by UV absorption,~1H NMR and MS.By changing the polymerization degree of PBzA,the incidence of head addition of BzA is estimated to be 0.14%.Based on the photodegradation ability of PVK,amphiphilic triblock copolymers PDMAEMA-PPVK-P(2-EHA)were prepared by RAFT polymerization using dimethylaminoethyl methacrylate(DMAEMA)and 2-ethylhexyl acrylate(2-EHA)as hydrophilic and hydrophobic monomers,respectively.And their application in the emulsion with photo-controlled drug release character was investigated.The degradation behaviors of PPVK and poly((4-methoxyl)phenyl vinyl ketone)(PMPVK)was compared and concluded that the degradation rate of PPVK is faster than PMPVK.Ethyl oleate was employed as oil phase to prepare an environmental-friendly W/O emulsion using PDMAEMA-P(2-EHA)as emulsifier,and the influences of volume ratio of oil and water,the structure and dosage of emulsifier and the pH of water phase on stability of emulsion were investigated.The results show that the emulsion can achieve good stability under the condition that the volume ratio of O/W is 2:1,the polymerization degree ratio of hydrophilic/hydrophobic segments of the block copolymer is 1:5,the dosage of block copolymer is 0.03 g/mL and the p H of water phase is 5.Later on,PDMAEMA-PPVK-P(2-EHA)was employed to prepare photosensitive emulsions,and the influence of the type of photodegradable polymers,the chain length of photodegradable segments and the dosage of emulsifier on the demulsification rate and drug release rate was investigated.The rate of demulsification and drug release was proved to increase by lengthening photodegradable chain length and decrease by raising emulsifier dosage.These results provide guidance for the preparation of photosensitive emulsion and drug release system of glyphosate.更多还原