Stability of the A15 phase in diblock copolymer melts
Stability of the A15 phase in diblock copolymer melts
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DOI：
10.1073/pnas.1900121116
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发表时间：
2019-07-02
影响因子：
11.1
通讯作者：
Bates, Christopher M.
中科院分区：
文献类型：
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作者：
Bates, Morgan W.;Lequieu, Joshua;Bates, Christopher M.
嵌段聚合物自组装成有序的纳米结构支撑了它们在基础和应用聚合物科学中的实用性，但对于最简单的 AB 型材料，只知道少数平衡形态。在这里，我们报告了在包含聚（丙烯酸十二烷基酯）-嵌段-聚（丙交酯）的单组分二嵌段共聚物熔体中发现了A15球相。对相空间的系统探索表明，A15 在位于西格玛球相和六方密堆积圆柱体之间的大量少数丙交酯块体积分数 (f(L) = 0.25 - 0.33）中形成。自洽场论将 A15 的热力学稳定性合理化为极端构象不对称的结果。实验观察到的 A15 无序相变不是使用平均场近似捕获的，而是由于成分波动而产生，如完全波动场理论模拟所证明的那样。实验和场论模拟的结合提供了合理的设计规则，可用于通过自组装生成独特的基于聚合物的中间相。
The self-assembly of block polymers into well-ordered nanostructures underpins their utility across fundamental and applied polymer science, yet only a handful of equilibrium morphologies are known with the simplest AB-type materials. Here, we report the discovery of the A15 sphere phase in single-component diblock copolymer melts comprising poly(dodecyl acrylate)-block-poly(lactide). A systematic exploration of phase space revealed that A15 forms across a substantial range of minority lactide block volume fractions (f(L) = 0.25 - 0.33) situated between the sigma-sphere phase and hexagonally close-packed cylinders. Self-consistent field theory rationalizes the thermodynamic stability of A15 as a consequence of extreme conformational asymmetry. The experimentally observed A15-disorder phase transition is not captured using mean-field approximations but instead arises due to composition fluctuations as evidenced by fully fluctuating field-theoretic simulations. This combination of experiments and field-theoretic simulations provides rational design rules that can be used to generate unique, polymer-based mesophases through self-assembly.