【作者】 尚成新；

【导师】 张天永；

【作者基本信息】 天津大学 ， 工业催化， 2013， 博士

【摘要】 自从1998年被首次报道以来，可逆加成-断裂链转移（RAFT）聚合凭借其在聚合物合成方面的优势，成为应用广泛的活性自由基聚合方法。截止目前，均相反应条件下的溶液RAFT聚合和本体RAFT聚合研究较多，各种均聚物和嵌段共聚物被合成出来，且分子量分布很窄。然而，在非均相体系中的RAFT聚合，特别是水相RAFT聚合，研究相对较少。本文借助碳酸钙（CaCO3）粒子实现了疏水性单体、亲水性单体在水相的可控RAFT聚合。利用水相RAFT聚合合成聚苯乙烯（PS）。疏水性单体的乳液聚合多采用乳化剂来稳定乳液，而乳化剂会带来各种问题。本研究中，将苯乙烯（St）单体和RAFT试剂BDMAT（S,S’-二(,’-二甲基-’’-乙酸)三硫代碳酸酯）加入到水中，在CaCO3的悬浮作用下，它们吸附在CaCO3粒子表面，可以在水相中进行可控RAFT自由基聚合。CaCO3/St重量比对水相RAFT聚合具有影响，CaCO3/St重量比提高时会提高St在水相中RAFT聚合的速率。水相RAFT聚合的动力学研究发现，[St]o/[BDMAT]o/[K2S2O8]o比例较低时，聚合速率较快。在水相RAFT聚合中，ln([M]o/[M])与时间呈线性关系，数均分子量Mn随着单体转化率提高而线性增加。与十二烷基硫酸钠（SDS）作乳化剂的传统乳液RAFT聚合对比后发现，水相RAFT聚合的速率比传统乳液RAFT聚合慢，但CaCO3存在时水相RAFT聚合可以实现活性聚合。聚N-异丙基丙烯酰胺（PNIPAM）在水相的RAFT合成。由于PNIPAM具有温敏性，当温度高于其低临界溶解温度时，会转变成疏水性的，因此PNIPAM的合成多在有机溶剂中进行。本研究中，CaCO3粒子存在下，在水相中实现了单体N-异丙基丙烯酰胺（NIPAM）的可控RAFT自由基聚合。考察了CaCO3/NIPAM重量比、RAFT试剂与引发剂比例的影响，进行了动力学实验。动力学研究显示，ln([M]o/[M])与时间呈线性关系，数均分子量Mn随着单体转化率提高而线性增加，聚合产物PNIPAM的分子量分布PDI都较低。这些结果说明实验所采用的水相RAFT聚合方法是活性可控的。采用水相RAFT聚合的方法制备了含有疏水链段和温敏链段的PNIPAM-b-PS-b-PNIPAM三嵌段共聚物，RAFT试剂为PNIPAM-TTC（聚N-异丙基丙烯酰胺-三硫代碳酸酯）。发现CaCO3粒子具有明显稳定反应体系的作用。CaCO3/St重量比对RAFT聚合速率有影响，当CaCO3/St重量比提高时，反应速率增加。动力学研究表明，ln([M]o/[M])与时间呈线性关系，数均分子量Mn随着单体转化率提高而线性增加，CaCO3粒子存在时共聚物的分子量分布明显降低。在大分子RAFT试剂PDMA-TTC（聚N,N-二甲基丙烯酰胺-三硫代碳酸酯）存在下，利用水相RAFT聚合的方法制备了含有疏水链段和亲水链段的PDMA-b-PS-b-PDMA三嵌段共聚物。发现CaCO3/St重量比对RAFT聚合速率有影响，当CaCO3/St重量比提高时，反应速率增加，但是对产物的分子量分布影响不大。动力学研究表明，ln([M]o/[M])与时间呈线性关系，数均分子量Mn随着单体转化率提高而线性增加，CaCO3粒子存在时可以提高反应速率并降低共聚物的分子量分布。更多还原

【Abstract】 Since initial introduced in1998, the reversible addition-fragmentation chaintransfer (RAFT) polymerization has proven to be perhaps the most versatile of thecontrolled/living radical polymerization methods. Up to now, RAFT polymerizationunder homogeneous condition (solution/bulk) has been extensively studied, andvarious polymers including homopolymer, and block polymer with narrow molecularweight distribution have been synthesized. However, the RAFT polymerization underheterogeneous conditions, especially the aqueous RAFT polymerization, is far frombeing perfectly accomplished. A new method to achieve well-controlled aqueousRAFT polymerization of hydrophobic monomer and hydrophilic monomer in thepresence of CaCO3particles were proposed.Polystyrene (PS) was synthesized by aqueous RAFT polymerization. Thesurfactant plays the crucial role to ensure stability of the emulsion. However, thesurfactant brings some side effects. In this paper, the RAFT agent ofS,S’-bis(,’-dimethyl-’’-acetic acid) trithiocarbonate (BDMAT) and St were addedinto water mediated with CaCO3particles, and it was found that they were adsorbedon the surface of CaCO3particles and well-controlled aqueous RAFT polymerizationwas performed. The weight ratio of CaCO3/St on the aqueous RAFT polymerizationwas investigated, and it was found that high CaCO3/St weight ratio led to fast aqueousRAFT polymerization. The aqueous RAFT polymerization kinetics was checked, andthe fast RAFT polymerization rate at low molar ratio of styrene/BDMAT/K2S2O8, thelinear ln([M]o/[M])-time plot, the linear increase in the number-average molecularweight with the monomer conversion, and the relatively low polydispersity index(PDI) values were demonstrated. The aqueous RAFT polymerization was comparedwith the general emulsion RAFT polymerization in the presence of the sodiumdodecyl sulfate (SDS) surfactant. It was found that the aqueous RAFT polymerizationseemed more valid than the emulsion RAFT polymerization, despite that aqueousRAFT polymerization ran slower than the general emulsion RAFT polymerization.Poly(N-isopropylacrylamide)(PNIPAM) was prepared by a new method.PNIPAM possesses a readily accessible lower critical solution temperature (LCST) inwater and the chains become hydrophobic above the LCST, so the polymerization ofPNIPAM demonstrates the need for organic solvents. In this paper, the aqueous RAFTpolymerization of N-isopropylacrylamide (NIPAM) was carried out successfully inthe presence of CaCO3particles. The weight ratio of CaCO3/NIPAM on the aqueous RAFT polymerization, the molar ratio of RAFT agent to initiator and thepolymerization kinetics were investigated. The linear ln([M]o/[M])-time plot, thelinear increase in the number-average molecular weight with monomer conversion,and the relatively low PDI values were demonstrated. The proposed method isbelieved to be a new strategy to achieve well-controlled aqueous RAFTpolymerization.PNIPAM-b-PS-b-PNIPAM was synthesized by aqueous RAFT polymerizationmediated with the macro-RAFT agent of PNIPAM-TTC, and the copolymer hadthermosensitive block and hydrophobic block. It was found that the polymerizationwas stable in the presence of CaCO3particles, and high CaCO3/St weight ratio led tofast aqueous RAFT polymerization. The aqueous RAFT polymerization kinetics waschecked, the linear ln([M]o/[M])-time plot, the linear increase in the number-averagemolecular weight with the monomer conversion, and the relatively low PDI values inthe presence of CaCO3particles were demonstrated.PDMA-b-PS-b-PDMA, which had hydrophilic block and hydrophobic block,was synthesized by aqueous RAFT polymerization mediated with the macro-RAFTagent of PDMA-TTC. It was found that high CaCO3/St weight ratio led to fastaqueous RAFT polymerization, however, the PDI of polymer had been little affected.The aqueous RAFT polymerization kinetics was checked, the linearln([M]o/[M])-time plot, the linear increase in the number-average molecular weightwith the monomer conversion were demonstrated. At the same time, in the presenceof CaCO3particles, the polymerization rate was fast and the PDI values were lowrelatively.更多还原