Department of Physics and Astronomy, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada.
Department of Surgery, The Center for Engineering in Medicine (CEM), Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114, USA.
J Chem Phys. 2020 May 29;152(20):204907. doi: 10.1063/1.5132928.
The phase behavior of semi-flexible polymers is integral to various contexts, from materials science to biophysics, many of which utilize or require specific confinement geometries as well as the orientational behavior of the polymers. Inspired by collagen assembly, we study the orientational ordering of semi-flexible polymers, modeled as Maier-Saupe worm-like chains, using self-consistent field theory. We first examine the bulk behavior of these polymers, locating the isotropic-nematic transition and delineating the limit of stability of the isotropic and nematic phases. This effort explains how nematic ordering emerges from the isotropic phase and offers insight into how different (e.g., mono-domain vs multi-domain) nematic phases form. We then clarify the influence of planar confinement on the nematic ordering of the polymers. We find that while the presence of a single confining wall does not shift the location of nematic transition, it aligns the polymers in parallel to the wall; above the onset of nematic transition, this preference tends to propagate into the bulk phase. Introducing a second, perpendicular, wall leads to a nematic phase that is parallel to both walls, allowing the ordering direction to be uniquely set by the geometry of the experimental setup. The advantage of wall-confinement is that it can be used to propagate mono-domain nematic phases into the bulk phase.
半柔性聚合物的相行为对于从材料科学到生物物理学的各种领域都至关重要，其中许多领域都利用或需要特定的限制几何形状以及聚合物的取向行为。受胶原蛋白组装的启发，我们使用自洽场理论研究了半柔性聚合物的取向有序性，这些聚合物被建模为 Maier-Saupe 虫状链。我们首先研究了这些聚合物的体相行为，确定了各向同性-向列相转变，并描绘了各向同性相和向列相的稳定性极限。这一努力解释了向列有序如何从各向同性相中出现，并深入了解了不同的（例如，单畴相和多畴相）向列相如何形成。然后，我们澄清了平面限制对聚合物向列有序性的影响。我们发现，虽然单个限制壁的存在不会改变向列转变的位置，但它会使聚合物与壁平行排列；在向列转变开始后，这种偏好倾向于在体相中传播。引入第二个垂直壁会导致与两个壁都平行的向列相，从而可以通过实验装置的几何形状唯一地确定取向方向。壁限制的优点是可以将单畴向列相传播到体相。
