A Robust Cross-Linking Strategy for Block Copolymer Worms Prepared via Polymerization-Induced Self-Assembly.
A Robust Cross-Linking Strategy for Block Copolymer Worms Prepared via Polymerization-Induced Self-Assembly.
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DOI：
10.1021/acs.macromol.6b00422
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发表时间：
2016-04-26
期刊：
影响因子：
5.5
通讯作者：
Saunders BR
中科院分区：
文献类型：
--
作者：
Lovett JR;Ratcliffe LP;Warren NJ;Armes SP;Smallridge MJ;Cracknell RB;Saunders BR
一种聚单甲基丙烯酸甘油（PGMA）链转移剂通过聚合诱导自组装（PISA）在浓水溶液中通过可逆加成-断裂链转移（RAFT）统计共聚，将2-羟丙基甲基丙烯酸酯（HPMA）与甲基丙烯酸缩水甘油酯（GlyMA）进行链扩展。通过将成核块的总聚合度固定在144，同时将其GlyMA含量从0到20 mol %变化，制备了一系列5个独立的蠕虫凝胶。1H NMR动力学表明GlyMA比HPMA消耗快得多，产生了接近PGMA稳定块的富含GlyMA的序列。温度依赖的振荡流变学研究表明，增加GlyMA含量会导致蠕虫凝胶的热响应性逐渐降低，对于含有20 mol % GlyMA的蠕虫，在冷却时没有观察到脱胶。利用3-氨基丙基三乙氧基硅烷（APTES）将GlyMA残基上的环氧基开环，通过与HPMA残基上的硅氧烷基团和/或羟基水解缩合制备核心交联蠕虫。也许令人惊讶的是，1H NMR分析表明，环氧胺反应和分子间交联发生在相似的时间尺度上。交联导致更硬的蠕虫凝胶，在冷却时不会发生脱胶。动态光散射研究和TEM分析对暴露于甲醇（两种块的良好溶剂）或阴离子表面活性剂的线性蠕虫进行了研究，结果表明蠕虫立即解离。相比之下，交联蠕虫在这种条件下保持完整，前提是蠕虫核含有至少10mol %的GlyMA。
A poly(glycerol monomethacrylate) (PGMA) chain transfer agent is chain-extended by reversible addition–fragmentation chain transfer (RAFT) statistical copolymerization of 2-hydroxypropyl methacrylate (HPMA) with glycidyl methacrylate (GlyMA) in concentrated aqueous solution via polymerization-induced self-assembly (PISA). A series of five free-standing worm gels is prepared by fixing the overall degree of polymerization of the core-forming block at 144 while varying its GlyMA content from 0 to 20 mol %. 1H NMR kinetics indicated that GlyMA is consumed much faster than HPMA, producing a GlyMA-rich sequence close to the PGMA stabilizer block. Temperature-dependent oscillatory rheological studies indicate that increasing the GlyMA content leads to progressively less thermoresponsive worm gels, with no degelation on cooling being observed for worms containing 20 mol % GlyMA. The epoxy groups in the GlyMA residues can be ring-opened using 3-aminopropyltriethoxysilane (APTES) in order to prepare core cross-linked worms via hydrolysis-condensation with the siloxane groups and/or hydroxyl groups on the HPMA residues. Perhaps surprisingly, 1H NMR analysis indicates that the epoxy–amine reaction and the intermolecular cross-linking occur on similar time scales. Cross-linking leads to stiffer worm gels that do not undergo degelation upon cooling. Dynamic light scattering studies and TEM analyses conducted on linear worms exposed to either methanol (a good solvent for both blocks) or anionic surfactant result in immediate worm dissociation. In contrast, cross-linked worms remain intact under such conditions, provided that the worm cores comprise at least 10 mol % GlyMA.