Advantages of Block Copolymer Synthesis by RAFT-Controlled Dispersion Polymerization in Supercritical Carbon Dioxide
Advantages of Block Copolymer Synthesis by RAFT-Controlled Dispersion Polymerization in Supercritical Carbon Dioxide
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DOI：
10.1021/ma401051e
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发表时间：
2013-09-10
期刊：
影响因子：
5.5
通讯作者：
Howdle, Steven M.
中科院分区：
文献类型：
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作者：
Jennings, James;Beija, Mariana;Howdle, Steven M.
可逆加成-断裂链转移(RAFT)控制的超临界二氧化碳(SCCO(2))分散聚合嵌段共聚物的合成显示出前所未有的封堵效率控制。对于PMMA-b-PBzMA和PMMA-b-PST，通过GPC去卷积、梯度聚合物洗脱色谱(GPEC)和GPC双RI/UV检测技术测量均聚物污染物来定量封堵效率。本文还提出了一种新的、有应用前景的GPC反褶积和广义预测纠缠相结合的方法。所有技术都表明，通过降低自由基浓度和目标分子量，封闭率得到了显著提高。估计值与PMMA-b-PBzMA的理论符合得很好(有时超过)。当反应条件优化时，SCCO2中的非均相过程似乎对嵌段共聚过程几乎没有造成进一步的阻碍。即使在MMA的高转化率(>；95%)和高相对分子质量的情况下，也可以获得高的封闭效率(高达82%)。这些数据与许多已发表的嵌段共聚物多相合成的报道相比是有利的。
Reversible addition-fragmentation chain transfer (RAFT)-controlled block copolymer synthesis using dispersion polymerization in supercritical carbon dioxide (scCO(2)) shows unprecedented control over blocking efficiency. For PMMA-b-PBzMA and PMMA-b-PSt the blocking efficiency was quantified by measuring homopolymer contaminants Using the techniques of GPC deconvolution, gradient polymer elution chromatography (GPEC), and GPC dual RI/UV detection. A new, promising method was also developed which combined GPC deconvolution and GPEC. All techniques showed that blocking efficiency was significantly improved by reducing the radical concentration and target molecular weight. Estimated values agreed well with (and occasionally exceeded) theory for PMMA-b-PBzMA. The heterogeneous process in scCO2 appeared to cause little or no further hindrance to the block copolymerization procedure when reaction conditions were optimized. High blocking efficiencies were achieved (up to 82%) even at high conversion of MMA (>95%) and high molecular weight. These data compare favorably to numerous published reports of heterogeneous syntheses of block copolymers.