Universal Scaling Behavior during Network Formation in Controlled Radical Polymerizations
Universal Scaling Behavior during Network Formation in Controlled Radical Polymerizations
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DOI：
10.1021/acs.macromol.9b02109
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发表时间：
2019-12-24
期刊：
影响因子：
5.5
通讯作者：
Appel, Eric A.
中科院分区：
文献类型：
--
作者：
Mann, Joseph L.;Rossi, Rachel L.;Appel, Eric A.
尽管支化和网络聚合物在生物、电子和流变学应用中无处不在，但预测乙烯基和多乙烯基单体聚合产生的网络结构仍然很困难。虽然受控自由基聚合（CRP）技术在（超）支化聚合物的合成中提供了模块化和控制，但仍然缺乏对网络形成的统一理解，从而提供可靠的预测能力。目前的限制是无法预测使用 CRP 合成（超）支化聚合物期间出现的数均分子量和重均分子量。本研究通过首先通过生长边界分析建立直觉来解决这一文献差距，即通过实验凝胶点测量某些环境因素（浓度、单体选择和交联剂选择）如何影响网络形成过程中的交联效率。然后，我们通过实验凝胶点归一化证明了支化聚合物合成中分子量的普遍缩放行为，这已由先前的文献实验证实。此外，该分析中采用的归一化揭示了使用 CRP 技术合成的网络的宏观机械性能的趋势。该分析中采用的凝胶点归一化既使高分子化学家能够使用 CRP 确定（超）支化聚合物的特定数均分子量和重均分子量，又证明了 CRP 在凝胶合成中的实用性。
Despite the ubiquity of branched and network polymers in biological, electronic, and rheological applications, it remains difficult to predict the network structure arising from polymerization of vinyl and multivinyl monomers. While controlled radical polymerization (CRP) techniques afford modularity and control in the synthesis of (hyper)branched polymers, a unifying understanding of network formation providing grounded predictive power is still lacking. A current limitation is the inability to predict the number and weight average molecular weights that arise during the synthesis of (hyper)branched polymers using CRP. This study addresses this literature gap through first building intuition via a growth boundary analysis on how certain environmental cues (concentration, monomer choice, and cross-linker choice) affect the cross-link efficiency during network formation through experimental gel point measurements. We then demonstrate, through experimental gel point normalization, universal scaling behavior of molecular weights in the synthesis of branched polymers corroborated by previous literature experiments. Moreover, the normalization employed in this analysis reveals trends in the macroscopic mechanical properties of networks synthesized using CRP techniques. Gel point normalization employed in this analysis both enables a polymer chemist to target specific number and weight average molecular weights of (hyper)branched polymers using CRP and demonstrates the utility of CRP for gel synthesis.