Filler-induced heterogeneous nucleation of polymer crystals investigated by molecular dynamics simulations
Filler-induced heterogeneous nucleation of polymer crystals investigated by molecular dynamics simulations
复制标题
通过分子动力学模拟研究填料诱导的聚合物晶体异质成核
DOI：
10.1016/j.polymer.2023.126113
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发表时间：
2023
期刊：
影响因子：
4.6
通讯作者：
Wadkin-Snaith D
中科院分区：
文献类型：
--
作者：
Wadkin-Snaith D
已知填料颗粒作为聚合物结晶的成核剂，但填料表面性质和聚合物结晶之间的联系还不是很清楚。在这项工作中，分子动力学模拟被用于研究均相和非均相聚合物的成核和结晶，使用具有键弯曲势的一般线性珠子弹簧聚合物模型。聚合物体系在高温下平衡，然后以恒定速率冷却。没有表面存在，具有刚性链的聚合物比柔性聚合物更容易结晶。结晶度是根据直链段的质量分数估计的，我们把直链段的质量分数等同于茎的质量分数。在温度T c时，密度、旋转半径和茎质量分数急剧增加。冷却后，系统被再加热，一些系统显示出迟滞，这些性能在T m / T / c熔化时急剧下降。对于较慢的加热速率，晶体生长发生在从玻璃化转变温度T g和T c之间的加热过程中，直到在T m熔化之前。发现各向同性表面的存在促进了柔性系统的结晶，而在体中没有结晶。其中，茎质量分数和tc随表面与聚合物珠之间相互作用强度的增加而增加。温度和结晶度随冷却速率的变化与实验结果一致。该模型捕获了聚合物结晶现象，并提供了对非均相成核的见解，表明强界面相互作用促进结晶，从而有助于选择或设计成核剂来控制聚合物结晶和微观结构。
Filler particles are known to act as nucleants for polymer crystallisation yet the connection between the filler surface properties and polymer crystallisation are not well understood. In this work, molecular dynamics simulations were used to investigate homogeneous and heterogeneous polymer nucleation and crystallisation using a generic linear bead–spring polymer model with a bond bending potential. The polymer systems were equilibrated at high temperature and then cooled at a constant rate. Without a surface present, polymers with stiff chains were found to crystallise more readily than more flexible polymers. The degree of crystallinity was estimated based on the mass fraction of straight chain segments which we equate to stem mass fraction. At a temperature T c a sharp increase in density, radius of gyration and stem mass fraction occurred. After cooling, the systems were reheated and some systems showed hysteresis with a sharp decrease in these properties occurring upon melting at T m> T c. For slower heating rates, crystal growth occurred during heating from between the glass transition temperature, T g, and T c until just before melting at T m. The presence of an isotropic surface was found to promote crystallisation in flexible systems that did not crystallise in the bulk, where the stem mass fraction and T c increased with the interaction strength between the surface and the polymer beads. Changes in T c and degree of crystallinity with cooling rate are consistent with experimental observations. This model captures polymer crystallisation phenomena and provides insight into heterogeneous nucleation, demonstrating that strong interfacial interactions promote crystallisation, thus aiding the choice or design of nucleants for control of polymer crystallisation and microstructure.
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