Xi Shun, Zhu Yiwei, Lu Jinxin, Chapman Walter G
Department of Chemical and Biomolecular Engineering, Rice University, Houston, Texas 77005, USA.
J Chem Phys. 2022 Feb 7;156(5):054902. doi: 10.1063/5.0069883.
The self-assembly of block copolymer melts and solutions with two-dimensional density inhomogeneity is studied using modified inhomogeneous statistical associating fluid theory (iSAFT). A real-space combinatorial screening method under density functional theory formalism is proposed and used to map out the phase diagram of block copolymer melts including order-disorder transitions and order-order transitions. The predicted phase diagram agrees well with molecular dynamics simulation and self-consistent field theory. The compressibility effect on order-disorder transition temperature for block copolymer melts is modeled using iSAFT. The pressure induced temperature change by theory has a similar trend to experimental studies. Then, the lyotropic and thermotropic self-assembly phase behavior of block copolymer solutions is investigated. Detailed density distributions by iSAFT provide insight into the lyotropic properties of the block copolymer solutions at the molecular level. The effect of the block copolymer molecular architecture is studied by comparing block copolymers with different molecular packing parameters. Block copolymer solutions in the inverted hexagonal phase are predicted by theory for the block copolymer having a large molecular packing parameter. Finally, solvent selectivity is studied by modeling the block copolymers in a neutral good solvent. The enhanced local solvent concentration predicted by theory explains the reason for fewer ordered phases found in experiments.
采用修正的非均匀统计缔合流体理论（iSAFT）研究了具有二维密度不均匀性的嵌段共聚物熔体和溶液的自组装。提出了一种密度泛函理论形式下的实空间组合筛选方法，并用于绘制包括有序-无序转变和有序-有序转变的嵌段共聚物熔体相图。预测的相图与分子动力学模拟和自洽场理论吻合良好。利用iSAFT对嵌段共聚物熔体的压缩性对有序-无序转变温度的影响进行了建模。理论上压力引起的温度变化趋势与实验研究相似。然后，研究了嵌段共聚物溶液的溶致和热致自组装相行为。iSAFT给出的详细密度分布在分子水平上深入了解了嵌段共聚物溶液的溶致性质。通过比较具有不同分子堆积参数的嵌段共聚物，研究了嵌段共聚物分子结构的影响。理论预测了具有大分子堆积参数的嵌段共聚物溶液处于反六角相。最后，通过对中性良溶剂中的嵌段共聚物进行建模研究了溶剂选择性。理论预测的局部溶剂浓度增强解释了实验中发现的有序相较少的原因。
