用半連續反應器和RAFT技術合成可控梯度聚合物

化工論文編號:HG216  論文字數:11056,頁數:31

目  錄
中文摘要 I
英文摘要 II
目錄 III
1 緒論 1
  1.1 研究背景、目的、意義及主要內容 1
  1.2 文獻綜述 2
      1.2.1 可控/活性自由基共聚合反應 2
      1.2.2 半連續反應器技術及應用 6
2 實驗部分 8
  2.1 原料來源及精制 8
       2.1.1 原料規格 8
       2.1.2 原料精制 8
  2.2 芐基二硫代異丁酸酯（BDIB）的制備 8
  2.3 聚合過程操作 9
       2.3.1 間歇聚合操作 9
       2.3.2 半連續聚合操作 9
  2.4 聚合實驗配方 10
  2.5 分析與表征 10
       2.5.1 聚合轉化率 10
       2.5.2 聚合物的分子量及其分布 10
       2.5.3 共聚物組成 11
3 結果和討論 12
  3.1 BDIB的結構表征 12
  3.2 BDIB調控下苯乙烯/丙烯酸丁酯共聚動力學 12
  3.3 St/BA梯度共聚物的合成 14
      3.3.1 Fnl=0.5且組成均一的St/BA共聚物的合成 15
      3.3.2 Fnl=0.5的St/BA線性梯度共聚物的合成 16
      3.3.3 Fnl=0.5的St/BA雙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 總結與展望 20
  4.1 總結 20
  4.2 展望 20
致謝 21
參考文獻 22
附錄 24

摘要：梯度共聚物是瞬時共聚組成從分子主鏈的一端到另一端連續變化的一類新型共聚物。為了實現瞬時組成沿分子主鏈連續變化，所有鏈必須同時引發，并在聚合過程中一直保持活性。可控/活性自由基聚合為梯度共聚物的制備提供了一種可能。但是，在間歇操作過程中，共聚單體進行可控/活性自由基聚合時，由于不同單體的競聚率不同，導致“組成漂移”，因此得到的是自發梯度共聚物。對于給定的共聚單體，其組成梯度僅僅取決于共聚單體的競聚率，因而結構是無法控制的。
 本文利用半連續進料法和可逆加成－斷裂連轉移聚合（reversible addition-fragmentation chain transfer，RAFT），設計合成了一系列具有精確可控組成曲線（組成均一，線性梯度，雙曲正切梯度和三嵌段（中間段為線性梯度））的St/BA共聚物，選用的RAFT試劑為芐基二硫代異丁酸酯（benzyl dithioisobutyrate，BDIB)。共聚單體的進料速率根據目標共聚物的組成－鏈長曲線通過動力學模型計算得到。所得共聚物的組成分布、分子量及分子量分布均與模型預測一致。而且聚合物的分子量分布較窄，分子量分布指數約為1.3。
關鍵詞: 半連續反應器；RAFT聚合；梯度共聚物；共聚組成

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