用半连续反应器和RAFT技术合成可控梯度聚合物

范文编号:HG216  范文字数:11056,页数:31

摘要：梯度共聚物是瞬时共聚组成从分子主链的一端到另一端连续变化的一类新型共聚物。为了实现瞬时组成沿分子主链连续变化，所有链必须同时引发，并在聚合过程中一直保持活性。可控/活性自由基聚合为梯度共聚物的制备提供了一种可能。但是，在间歇操作过程中，共聚单体进行可控/活性自由基聚合时，由于不同单体的竞聚率不同，导致“组成漂移”，因此得到的是自发梯度共聚物。对于给定的共聚单体，其组成梯度仅仅取决于共聚单体的竞聚率，因而结构是无法控制的。
 本文利用半连续进料法和可逆加成－断裂连转移聚合（reversible addition-fragmentation chain transfer，RAFT），设计合成了一系列具有精确可控组成曲线（组成均一，线性梯度，双曲正切梯度和三嵌段（中间段为线性梯度））的St/BA共聚物，选用的RAFT试剂为苄基二硫代异丁酸酯（benzyl dithioisobutyrate，BDIB)。共聚单体的进料速率根据目标共聚物的组成－链长曲线通过动力学模型计算得到。所得共聚物的组成分布、分子量及分子量分布均与模型预测一致。而且聚合物的分子量分布较窄，分子量分布指数约为1.3。
关键词: 半连续反应器；RAFT聚合；梯度共聚物；共聚组成

Abstract: Gradient copolymers are copolymers in which the instantaneous composition varies continuously along the chain contour, that is, gradient copolymers have a continuous change in composition from one end of the chain to the other.  In order to achieve this continuous change in instantaneous composition, all chains must be initiated simultaneously, and must survive until the end of the polymerization.  The recent emergence of techniques for implementing living radical polymerization has provided a new set of tools for polymer chemists that allow preparing the gradient copolymers.  However, controlled/living radical copolymerization (CLRcoP) operated in batch experiences composition drifting and thus produces spontaneous gradient copolymer.  The composition profile along chain length of individual chains is solely determined by the reactivities of comonomers and the as-synthesized product is uncontrolled.
 In this work, a novel series of styrene/butyl acrylate (St/BA) copolymers with precisely designed composition profiles (uniform, linear gradient, tanh gradient, and tri-block with a linear gradient mid-block) were produced using a semi-batch reversible addition-fragmentation chain transfer (RAFT) copolymerization mediated by benzyl dithioisobutyrate (BDIB).  The comonomer feeding rate was programmed based on a kinetic model with the targeted composition profile as an objective functions.  The experimental composition and molecular weight profiles agreed very well with the model predictions.  The polymer molecular weight distributions were narrow with polydispersity index values about 1.3.
Key words: Semi-batch reactor system; RAFT polymerization; Gradient copolymer; Copolymer composition
目  录
中文摘要 I
英文摘要 II
目录 III
1 绪论 1
  1.1 研究背景、目的、意义及主要内容 1
  1.2 文献综述 2
      1.2.1 可控/活性自由基共聚合反应 2
      1.2.2 半连续反应器技术及应用 6
2 实验部分 8
  2.1 原料来源及精制 8
       2.1.1 原料规格 8
       2.1.2 原料精制 8
  2.2 苄基二硫代异丁酸酯（BDIB）的制备 8
  2.3 聚合过程操作 9
       2.3.1 间歇聚合操作 9
       2.3.2 半连续聚合操作 9
  2.4 聚合实验配方 10
  2.5 分析与表征 10
       2.5.1 聚合转化率 10
       2.5.2 聚合物的分子量及其分布 10
       2.5.3 共聚物组成 11
3 结果和讨论 12
  3.1 BDIB的结构表征 12
  3.2 BDIB调控下苯乙烯/丙烯酸丁酯共聚动力学 12
  3.3 St/BA梯度共聚物的合成 14
      3.3.1 Fnl=0.5且组成均一的St/BA共聚物的合成 15
      3.3.2 Fnl=0.5的St/BA线性梯度共聚物的合成 16
      3.3.3 Fnl=0.5的St/BA双曲正切梯度共聚物的合成 17
      3.3.4 BA-b-(BA-gradient-St)-b-St的合成 18
4 总结与展望 20
  4.1 总结 20
  4.2 展望 20
致谢 21
参考文献 22
附录 24

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