Department of Chemical Engineering, University of California, Santa Barbara, CA 93106.
Materials Research Laboratory, University of California, Santa Barbara, CA 93106.
Proc Natl Acad Sci U S A. 2019 Apr 23;116(17):8224-8232. doi: 10.1073/pnas.1900435116. Epub 2019 Apr 4.
Coacervation is a common phenomenon in natural polymers and has been applied to synthetic materials systems for coatings, adhesives, and encapsulants. Single-component coacervates are formed when block polyampholytes exhibit self-coacervation, phase separating into a dense liquid coacervate phase rich in the polyampholyte coexisting with a dilute supernatant phase, a process implicated in the liquid-liquid phase separation of intrinsically disordered proteins. Using fully fluctuating field-theoretic simulations using complex Langevin sampling and complementary molecular-dynamics simulations, we develop molecular design principles to connect the sequenced charge pattern of a polyampholyte with its self-coacervation behavior in solution. In particular, the lengthscale of charged blocks and number of connections between oppositely charged blocks are shown to have a dramatic effect on the tendency to phase separate and on the accessible chain conformations. The field and particle-based simulation results are compared with analytical predictions from the random phase approximation (RPA) and postulated scaling relationships. The qualitative trends are mostly captured by the RPA, but the approximation fails catastrophically at low concentration.
凝聚是一种常见的自然聚合物现象，并已被应用于涂料、粘合剂和封装材料等合成材料系统。当嵌段聚两性电解质表现出自凝聚时，单一组分凝聚物就会形成，相分离成富含聚两性电解质的致密液相凝聚物，同时存在稀的上清液相，这一过程涉及到无序蛋白质的液-液相分离。我们使用复杂朗之万采样的全涨落场论模拟和互补的分子动力学模拟，开发了分子设计原则，将聚两性电解质的序列电荷模式与其在溶液中的自凝聚行为联系起来。特别是，带电块的长度尺度和带相反电荷块之间的连接数量对相分离的趋势和可及的链构象有显著影响。场和基于粒子的模拟结果与随机相位近似（RPA）的分析预测和假设的标度关系进行了比较。RPA 主要捕捉到了定性趋势，但在低浓度下，该近似灾难性地失效。
