Mesoscopic simulations of thermally-induced phase separation in PVDF/DPC solutions
Mesoscopic simulations of thermally-induced phase separation in PVDF/DPC solutions
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DOI：
10.1016/j.memsci.2019.02.014
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发表时间：
2019-05-01
影响因子：
9.5
通讯作者：
Millett, Paul C.
中科院分区：
文献类型：
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作者：
Cervellere, M. Rosario;Tang, Yuan-hui;Millett, Paul C.
我们提出了聚合物溶液中热致相分离的相场模型，并针对聚偏二氟乙烯 (PVDF)/碳酸二苯酯 (DPC) 系统进行了校准。对各向同性和各向异性热淬火进行了大规模三维计算机模拟，并分析了所得两相形态的演变和结构。进行各向同性淬火，其中温度均匀地降低到双节温度以下，以了解富聚合物相和贫聚合物相随时间的引发和粗化。还进行了各向异性淬火，即系统从一个特定表面冷却，以了解特征域尺寸的梯度如何在不同条件下发展。在这些各向异性淬火中，我们观察到在冷却表面附近形成致密表层，其厚度取决于几个参数，包括聚合物体积分数、冷却表面保持的假设浴温以及通过聚合物溶液的热传导速率。通过修改两个物种特有的热力学和动力学参数，该模型可以适用于其他聚合物/溶剂系统。
We present a phase-field model of thermally-induced phase separation in polymer solutions, calibrated for the polyvinylidene fluoride (PVDF)/diphenyl carbonate (DPC) system. Large-scale three-dimensional computer simulations were performed for isotropic and anisotropic thermal quenches, and the evolution and structure of the resulting two-phase morphology is analyzed. Isotropic quenches, in which the temperature is uniformly reduced below the binodal temperature, were conducted to understand the initiation and coarsening of the polymer-rich and polymer-poor phases throughout time. Anisotropic quenches, in which the system is cooled from one particular surface, were also conducted to understand how gradients in the characteristic domain size develop for varying conditions. In these anisotropic quenches, we observe the formation of a dense skin layer adjacent to the cooling surface, the thickness of which depends on several parameters including the polymer volume fraction, the assumed bath temperature that is maintained at the cooling surface, and the rate of thermal conduction through the polymer solution. The model here can be adapted to other polymer/solvent systems by modifying the thermodynamic and kinetic parameters specific to the two species.