Pluronics, also known as poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) (PEO–PPO–PEO) block copolymers (BCP), are recognized for their ability to self-assemble into diverse mesophases, making them valuable in designing materials with tailored properties for applications in drug delivery and nanotechnology. Although the formation of these self-assembled structures is achieved by the widely utilized method of modulating the solvent–cosolvent composition, a comprehensive understanding of their underlying mechanism and phase transition behavior still remains elusive. Here, we used coarse-grained molecular dynamics simulations to explore the self-assembly of different triblock copolymers in a water/ethanol mixture with different compositions. The investigation includes an exploration of the impact of BCP concentration and the PPO/PEO block ratio on cosolvent-induced self-assembly. The outcomes unveil a diverse array of mesophases formed by BCP within the ternary BCP/water/ethanol mixture. We observed that the cosolvent-induced morphological transitions are governed by the selective affinity of PPO and PEO blocks toward the solvent and cosolvent. It also alters the local chemical environment and conformational changes in individual BCP chains. Additionally, we find that the influence of solvent–cosolvent composition is significant at low BCP composition, instigating an unimeric-to-micellar phase transition, while at high BCP composition, the PPO/PEO block ratio dominates the effect of solvent–cosolvent composition and determines the self-assembled morphology. Our results offer fundamental insights, serving as a guide to control the morphology of BCP self-assembly by fine-tuning the solvent–cosolvent ratio.

中文翻译：

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利用分子动力学模拟分析嵌段共聚物浓度和水乙醇比对 Pluronics 相变的影响


Pluronics，也称为聚（环氧乙烷）-聚（环氧丙烷）-聚（环氧乙烷）（PEO-PPO-PEO）嵌段共聚物 （BCP），因其能够自组装成不同的中间相而得到认可，这使得它们在设计具有定制特性的材料方面很有价值，用于药物递送和纳米技术应用。尽管这些自组装结构的形成是通过广泛使用的调节溶剂-助溶剂成分的方法实现的，但对其潜在机制和相变行为的全面理解仍然难以捉摸。在这里，我们使用粗粒度分子动力学模拟来探索不同成分的三嵌段共聚物在水/乙醇混合物中的自组装。该研究包括探索 BCP 浓度和 PPO/PEO 阻断率对助溶剂诱导的自组装的影响。结果揭示了 BCP 在三元 BCP/水/乙醇混合物中形成的多种中间相。我们观察到助溶剂诱导的形态转变受 PPO 和 PEO 嵌段对溶剂和助溶剂的选择性亲和力控制。它还会改变单个 BCP 链中的局部化学环境和构象变化。此外，我们发现溶剂-助溶剂组成的影响在低 BCP 组成下显着，引发单纯晶系到胶束相变，而在高 BCP 组成下，PPO/PEO 嵌段比主导溶剂-助溶剂组成的影响并决定自组装形态。我们的结果提供了基本见解，可作为通过微调溶剂-助溶剂比来控制 BCP 自组装形态的指南。