Morphology and thermodynamics of polymers with monofunctional hydrogen bonding ends in dilute and semidilute concentration.
Morphology and thermodynamics of polymers with monofunctional hydrogen bonding ends in dilute and semidilute concentration.
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DOI：
10.1103/physreve.100.012502
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发表时间：
2019-07
期刊：
影响因子：
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通讯作者：
Eunsang Lee;W. Paul
中科院分区：
文献类型：
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作者：
Eunsang Lee;W. Paul
超分子聚合物 (SMP) 的流变特性取决于其平衡结构，包括聚集体的尺寸、数量和拓扑结构。两端带有氢键 (H-bonding) 基序的聚合物是一种广泛使用的构建 SMP 的前体。由于链刚度、氢键相互作用、沿链的极性和聚合物构象熵之间复杂的相互作用，很难从理论上预测 SMP 的结构。在这项工作中，我们研究了各种密度下具有氢键末端的 SMP 的热力学。使用具有聚乙烯和聚丁二醇粗粒度模型的复制品交换随机近似蒙特卡罗方法。我们的模拟表明，随着温度升高，SMP 具有两种形态转变线：环-线性转变和线性-自由链转变。后者是热力学转变并且是连续的。比较两种不同的间隔物，我们发现由于成环概率不同，在恒定体积分数下环线转变温度彼此不同，这可以通过平均场从平均聚合物尺寸计算出来。然而，线性自由链的转变温度相似，因为形成氢键的熵损失主要取决于在系统中找到氢键基团的概率，这对于给定体积分数的两个系统是相同的。
Rheological properties of supramolecular polymers (SMPs) depend on their equilibrium structure including the size, the number, and the topology of aggregates. A polymer with a hydrogen bonding (H-bonding) motif at both ends is one widely used precursor to build SMPs. Due to the complex interplay between chain stiffness, H-bonding interaction, polarity along a chain, and polymer conformational entropy, it is difficult to theoretically predict the structure of SMPs. In this work we investigate thermodynamics of SMPs with H-bonding ends in a wide range of densities. A replica exchange stochastic approximation Monte Carlo method with coarse-grained models for polyethylene and polybuthylene glycols is used. Our simulation shows that SMPs have two morphological transition lines with increasing temperature, a ring-linear transition, and a linear-free chain transition. The latter is a thermodynamic transition and turns out to be continuous. Comparing the two different spacers, we find that ring-linear transition temperatures differ from each other at the constant volume fraction due to different looping probabilities, which can be calculated from the average polymer size by mean field. However, the linear-free chain transition temperatures are similar because the entropic penalty to form a hydrogen bond mainly depends on the probability of finding H-bonding groups in a system, which is the same for both systems at a given volume fraction.