Free-energy landscapes of semiflexible theta-polymer aggregation with and without external force

有外力和无外力的半柔性θ聚合物聚集的自由能景观

• 批准号: 277838335
• 负责人: Professor Dr. Wolfhard Janke
• 金额: --
• 依托单位: Institut für Theoretische Physik
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2015
• 资助国家: 德国
• 起止时间: 2014-12-31 至 2020-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/277838335?language=en
• 关键词: Free; energy; landscapes; semiflexible; theta

The main objective of this project is to explore universal aspects of semiflexible polymer aggregation with and without external force. The focus will be on generic structural properties rooted in statistical physics and free-energy landscapes of grafted semiflexible polymers subject to an external force. The analysis will rely on numerical data obtained with carefully tailored multicanonical computer simulations.We aim to investigate finite-size effects of semiflexible polymer aggregation in periodic boundary conditions and apply finite-size scaling theory to draw universal conclusions. Emphasis will be laid on the free-energy landscape, especially characterizing the scaling of the free-energy barrier with chain number, in dependence on the stiffness of the polymers. This approach in the mesoscopic range should allow us to distinguish different aggregate morphologies and may be used as a protocol for phase transitions with mixed phases, in general. Since the aggregation transition separatesenergy-dominated compact structures from an entropy-dominated soluble regime, this demands systems at low density and sophisticated simulation methods that allow efficient sampling of both energy and entropy contributions as well as sophisticated analysis tools to disentangle them.Motivated by experimental realizations of polymer bundles under force, we plan to study the conformational properties of grafted semiflexible polymers with and without pulling force. Determining the free-energy landscape and the associated free-energy barrier will allow the characterization of the involved transitions from disordered to amorphous or bundle (tower) phases. With an external force, wewill focus on rather flexible polymers where we expect an intermediate force regime in which the competition between self-attraction, mutual attraction and pulling force should give rise to bundles with a helical twist. In this case, we want to test if the worm-like chain approximation (which is well-applicable to rather stiff polymer bundles) becomes valid for flexible polymer bundles underexternal force.This will be extended for a few grafted polymers to a setup with an external field where we aim to study the free-energy landscape as a function of both temperature and field. Considering also alternating fields allows a glimpse at steady-state properties, where we want to identify relevant length scalesthrough finite-size scaling. Attaching extended geometric objects to the non-grafted polymer ends introduces additional constraints and may lead to interesting and promising experimental setups.

这个项目的主要目标是探索半柔性聚合物聚集的普遍性方面，有和没有外力。重点将是植根于统计物理学和接枝半柔性聚合物受外力的自由能景观的通用结构特性。该分析将依赖于精心定制的multicanonical计算机simulation.We的目的是调查在周期性边界条件下的半柔性聚合物聚集的有限尺寸效应，并应用有限尺寸标度理论得出普遍的结论获得的数值数据。重点将放在自由能景观，特别是表征的自由能势垒与链数的缩放，在依赖于聚合物的刚度。在介观范围内的这种方法应该使我们能够区分不同的聚集体形态，并可用作混合相的相变协议，在一般情况下。由于聚集转变将能量主导的紧凑结构与熵主导的可溶性区域分开，这需要低密度的系统和复杂的模拟方法，这些方法允许对能量和熵贡献进行有效采样，以及复杂的分析工具来解开它们。我们计划研究有和没有拉力的接枝半柔性聚合物的构象性质。确定的自由能景观和相关的自由能势垒将允许所涉及的从无序到无定形或束（塔）相的过渡的表征。与外力，我们将集中在相当灵活的聚合物中，我们预计一个中间的力制度，自吸引力之间的竞争，相互吸引力和拉力应该引起束与螺旋扭曲。在这种情况下，我们想测试蠕虫状链近似（这是很好地适用于相当刚性的聚合物束）变得有效的柔性聚合物束underexternal力，这将是几个接枝聚合物的设置与外部领域，我们的目标是研究自由能景观作为一个函数的温度和字段。考虑交变场也允许在稳态特性一瞥，在那里我们要确定相关的长度scalesthrough有限尺寸scaling。将扩展的几何对象附加到非接枝聚合物末端引入了额外的约束，并可能导致有趣和有前途的实验设置。