Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States.
ACS Macro Lett. 2021 Aug 17;10(8):1029-1034. doi: 10.1021/acsmacrolett.1c00382. Epub 2021 Jul 22.
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(-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.
疏水性的作用，特别是非离子疏水性共聚单体在聚电解质复合凝聚物的相行为中的作用还没有得到很好的理解。在这里，我们通过合成一系列具有广泛电荷密度和非离子疏水性侧链长度的聚合物来解决这个问题，并通过光浊度法来表征它们的相行为。这些聚合物是通过聚(-丙烯酰氧基琥珀酰亚胺)的后聚合修饰得到的，目标电荷密度在 40%到 100%之间，非离子脂肪族侧链的长度从 0 到 12 个碳原子。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的配对浊度测量显示出一种复杂的盐响应，具有明显的电荷密度主导和疏水性主导区域。聚合物的溶解度与凝聚物的相行为没有直接的相关性，这表明从聚合物-水相互作用参数的角度来理解凝聚物的相行为是困难的。这一结果表明，进一步研究特定的分子尺度相互作用如何调节复杂凝聚物的相行为还有很大的空间。
