The role of hydrophobicity, and particularly of nonionic hydrophobic comonomers, in the phase behavior of polyelectrolyte complex coacervates is not well-understood. Here, we address this problem by synthesizing a library of polymers with a wide range of charge densities and nonionic hydrophobic side chain lengths, and characterizing their phase behavior by optical turbidity. The polymers were prepared by postpolymerization modification of poly(N-acryloxy succinimide), targeting charge densities between 40 and 100% and nonionic aliphatic side chains with lengths from 0 to 12 carbons long. Turbidity measurements on pairs of polycations and polyanions with matched charge densities and nonionic side chain lengths revealed a complex salt response with distinct charge density-dominated and hydrophobicity-dominated regimes. The polymer solubilities were not directly correlated with the phase behavior of the coacervates, indicating the difficulty of understanding the coacervate phase behavior in terms of the polymer–water interaction parameter. This result suggests that there is significant room for further work to understand the mechanisms by which specific molecular-scale interactions moderate the phase behavior of complex coacervates.

中文翻译：

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复杂凝聚层相行为中的电荷密度和疏水性主导机制

疏水性，特别是非离子疏水性共聚单体在聚电解质复合凝聚层相行为中的作用尚不清楚。在这里，我们通过合成具有各种电荷密度和非离子疏水侧链长度的聚合物库，并通过光学浊度表征它们的相行为来解决这个问题。聚合物通过聚( N )的后聚合改性制备-丙烯酰氧基琥珀酰亚胺），目标电荷密度在 40% 到 100% 之间，非离子脂肪族侧链的长度为 0 到 12 个碳。对具有匹配电荷密度和非离子侧链长度的聚阳离子和聚阴离子对的浊度测量揭示了复杂的盐响应，具有不同的电荷密度主导和疏水性主导的方案。聚合物溶解度与凝聚层的相行为没有直接关系，表明很难根据聚合物-水的相互作用参数来理解凝聚层的相行为。这一结果表明，在了解特定分子尺度相互作用调节复杂凝聚层相行为的机制方面还有很大的工作空间。