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Precision synthesis of functional materials via RAFT polymerization and click-type chemical reactions.

机译：通过RAFT聚合和点击型化学反应精确合成功能材料。

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摘要

The need to tailor polymeric architectures with specific physico-chemical properties via the simplest, cleanest, and most efficient synthetic route possible has become the ultimate goal in polymer synthesis. Recent progress in macromolecular science, such as the discoveries of controlled/"living" free radical polymerization (CRP) methods, has brought about synthetic capabilities to prepare (co)polymers with advanced topologies, predetermined molecular weights, narrow molecular weight distributions, and precisely located functional groups. In addition, the establishment of click chemistry has redefined the selected few highly efficient chemical reactions that become highly useful in post-polymerization modification strategies. Hence, the ability to make well-defined topologies afforded by controlled polymerization techniques and the facile incorporation of functionalities along the chain via click-type reactions have yielded complex architectures, allowing the investigation of physical phenomena which otherwise could not be studied with systems prepared via conventional methods.;The overarching theme of the research work described in this dissertation is the fusion of the excellent attributes of reversible addition-fragmentation chain transfer (RAFT) polymerization method, which is one of the CRP techniques, and click-type chemical reactions in the precision of synthesis of advanced functional materials. Chapter IV is divided into three sections.;In Section I, the direct RAFT homopolymerization of 2-(acryloyloxy)ethyl isocyanate (AOI) and subsequent post-polymerization modifications are described. The polymerization conditions were optimized in terms of the choice of RAFT chain transfer agent (CTA), polymerization temperature and the reaction medium. Direct RAFT polymerization of AOI requires a neutral CTA, and relatively low reaction temperature to yield AOI homopolymers with low polydispersities. Efficient side-chain functionalization of PAOI homopolymers was achieved via reaction with model amine, thiol and alcohol compounds yielding urea, thiourethane and urethane derivatives, respectively. Reactions with amines and thiols (in the presence of base) were rapid, quantitative and efficient. However, the reaction with alcohols catalyzed by dibutyltin dilaurate (DBTDL) was relatively slow but proceeded to completion. Selective reaction pathways for the addition of difunctional ethanolamine and mercaptoethanol were also investigated.;A related strategy is described in Section II wherein a hydroxyl-containing diblock copolymer precursor was transformed into a library of functional copolymers via two sequential post-polymerization modification reactions. A diblock copolymer scaffold, poly[(N,N-dimethylacrylamide)-b-( N-(2-hydroxyethyl)acrylamide] (PDMA-b-PHEA) was first prepared. The hydroxyl groups of the HEA block were then reacted with 2-(acryloyloxy)ethylisocyanate (AOI) and allylisocyanate (AI) resulting in acrylate- and allyl-functionalized copolymer precursors, respectively. The efficiencies of Michael-type and free radical thiol addition reactions were investigated using selected thiols having alkyl, aryl, hydroxyl, carboxylic acid, amine and amino acid functionalities. The steps of RAFT polymerization, isocyanate-hydroxyl coupling and thiol-ene addition are accomplished under mild conditions, thus offering facile and modular routes to synthesize functional copolymers.;The synthesis and solution studies of pH- and salt-responsive triblock copolymer are described in Section III. This system is capable of forming self-locked micellar structures which may be controlled by changing solution pH as well as ionic strength. A triblock copolymer containing a permanently hydrophilic poly(N,N-dimethylacrylamide) (PDMA) outer block, a salt-sensitive zwitterionic poly(3[2-(N-methylacrylamido)ethyl dimethylammonio]propanesulfonate) (PMAEDAPS) middle block and a pH-responsive 3-acrylamido-3-methylbutanoic acid (PAMBA) core block was synthesized using aqueous RAFT polymerization. A facile formation of "self-locking" shell cross-linked micelles is achieved by changing solution pH and salt concentration. The reversible "self-locking" is attained from the interactions of zwitterionic groups in the middle block that constitutes the shell of the micelles. The structure slowly dissociates into unimers in 2-3 days at pH above the pKa of the PAMBA block.
机译：通过最简单，最清洁和最有效的合成途径来定制具有特定物理化学性质的聚合物结构的需求已成为聚合物合成的最终目标。大分子科学的最新进展，例如受控/“活性”自由基聚合（CRP）方法的发现，已经带来了合成能力，可以制备具有高级拓扑结构，预定分子量，窄分子量分布且精确的（共）聚合物定位的功能组。此外，点击化学的建立重新定义了所选的几种高效化学反应，这些反应在聚合后修饰策略中非常有用。因此，通过受控聚合技术提供的定义明确的拓扑结构的能力以及通过点击型反应沿链轻松整合功能的能力产生了复杂的体系结构，从而允许研究物理现象，否则无法通过使用本文描述的研究工作的总体主题是可逆加成-断裂链转移（RAFT）聚合方法（CRP技术之一）与点击式化学反应的优良特性的融合。先进功能材料的合成精度。第四章分为三个部分：第一部分，描述了异氰酸2-（丙烯酰氧基）乙酯（AOI）的直接RAFT均聚反应和随后的聚合后修饰。根据RAFT链转移剂（CTA）的选择，聚合温度和反应介质来优化聚合条件。 AOI的直接RAFT聚合需要中性的CTA和相对较低的反应温度才能产生具有低多分散性的AOI均聚物。通过与模型胺，硫醇和醇类化合物反应，分别生成尿素，硫代氨基甲酸酯和氨基甲酸酯衍生物，可以实现PAOI均聚物的高效侧链官能化。与胺和硫醇的反应（在碱的存在下）是快速，定量和有效的。然而，二月桂酸二丁锡（DBTDL）催化的与醇的反应相对较慢，但已完成。还研究了添加双官能乙醇胺和巯基乙醇的选择性反应途径。在第二节中描述了一种相关策略，其中通过两个连续的后聚合修饰反应将含羟基的二嵌段共聚物前体转化为官能共聚物库。首先制备了一种二嵌段共聚物支架，聚[（N，N-二甲基丙烯酰胺）-b-（N-（2-羟乙基）丙烯酰胺]（PDMA-b-PHEA），然后将HEA嵌段的羟基与2 -（丙烯酰氧基）乙基异氰酸酯（AOI）和烯丙基异氰酸酯（AI）分别生成丙烯酸酯和烯丙基官能化的共聚物前体。使用选择的具有烷基，芳基，羟基，羧酸，胺和氨基酸的官能团； RAFT聚合，异氰酸酯-羟基偶联和硫醇-烯加成的步骤均在温和的条件下完成，从而为合成功能性共聚物提供了简便而模块化的途径。盐反应性三嵌段共聚物将在第III部分中进行描述，该系统能够形成自锁胶束结构，可通过改变溶液的pH值和离子强度来控制胶束结构。共聚物，其中包含永久亲水的聚（N，N-二甲基丙烯酰胺）（PDMA）外嵌段，盐敏感性两性离子聚（3 [2-（N-甲基丙烯酰胺基）乙基二甲基铵]丙烷磺酸盐（PMAEDAPS）中间嵌段和pH响应型使用水性RAFT聚合合成3-丙烯酰胺基-3-甲基丁酸（PAMBA）核心嵌段。通过改变溶液的pH值和盐浓度，可以轻松形成“自锁”壳交联胶束。可逆的“自锁”是从构成胶束壳的中间嵌段中的两性离子基团的相互作用获得的。在高于PAMBA嵌段pKa的pH下，该结构在2-3天之内缓慢解离为单体。

著录项

  • 作者

    Flores, Joel Diez.;

  • 作者单位

    The University of Southern Mississippi.;

  • 授予单位 The University of Southern Mississippi.;
  • 学科 Chemistry Polymer.;Engineering Materials Science.
  • 学位 Ph.D.
  • 年度 2011
  • 页码 187 p.
  • 总页数 187
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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