Molecular Studies of Phase Transitions in Soft Matter - Melting and Crystallization Processes

软物质相变的分子研究 - 熔化和结晶过程

• 批准号: RGPIN-2018-06126
• 负责人: Soldera, Armand
• 金额: $ 3.5万
• 依托单位: Université de Sherbrooke
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2018
• 资助国家: 加拿大
• 起止时间: 2018-01-01 至 2019-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=665562
• 关键词: Molecular; Studies; Phase; Transitions; Soft

The foundations of polymer melting and crystallization have experienced a profound shift in recent years, as new experimental findings have emerged and/or revisit of established theories have been proposed, leading to a reconsideration of the underlying mechanisms for these phenomena. It has became urgent to better grasp this problematic since impacts are anticipated not only in fundamental science, but also in technological applications, a link that is more and more fostered in Canada. The novel perspective we wish to bring with this proposal addresses the matter thanks to a new approach to study phase transitions such as glass, spinodal, as well as mesophase and nanocrystal melting transitions. Our methodology relies on the use of an all-atom simulation approach. ***Reporting the experimental melting, Tm, and crystallization, Tc, temperatures with respect to the inverse of the crystal lamellar thickness, leads to two straight lines, but with different slopes. Accordingly there is an intersect at a finite thickness leading to an unexpected result where Tc becomes higher than Tm. To justify this outcome, it has been argued that the crystal development occurs into two steps. Crystallites form first, followed by a change into lamellar crystallites. The multi-step process for the entangled chains to crystallize was proposed by Strobl leading to the formation of a mesophase. We will thus intend to take advantage of the all-atom simulation in solving phase transition problems to handle this particular behavior. The central question this proposal aims to address is thus: Is the crystallization line achievable by all-atom simulation? To address this issue, we propose two axis: 1) Improve the modeled systems used to reveal the melting line; 2) Establish a procedure to get crystals from systems melt according to the procedure discussed in Axis 1. Simultaneaously, studies on mesophases, a component of crystallization according to the Strobl's model, and the glass transition, intimately linked to the study of semi-crystalline polymers, continue. Accordingly, beneath studying the crystallization line from simulation, we claim that a broad range of studies regarding melting, crystallization, mesophases, glass transition will be impacted. As a characteristic question this proposal can ultimately address, is: Is there a justification of the empircal link between the melting and the glass transition temperatures, the ratio usually ranges between 1.2 and 1.3. In conclusion, this experimental approach of simulation exploited in this proposal, is increasingly recognized as a third way of doing science. It is thus very innovative, and provides multidisciplinary training to HQP, a vital role nowadays in the job market.

近年来，随着新的实验结果的出现和/或对既定理论的重新审视，聚合物熔融和结晶的基础经历了深刻的转变，导致人们重新考虑这些现象的潜在机制。 更好地解决这个问题已经变得迫在眉睫，因为预计影响不仅会影响基础科学，而且还会影响技术应用，而加拿大越来越重视这一联系。 我们希望通过该提案带来的新颖视角解决了这个问题，这要归功于研究相变（例如玻璃、旋节线以及中间相和纳米晶体熔化转变）的新方法。我们的方法依赖于全原子模拟方法的使用。 ***报告实验熔化 Tm 和结晶 Tc（相对于晶体片层厚度的倒数的温度）导致两条直线，但斜率不同。因此，在有限厚度处存在交叉，导致 Tc 变得高于 Tm 的意外结果。 为了证明这一结果的合理性，有人认为晶体的发育分为两个步骤。首先形成微晶，然后转变为层状微晶。 Strobl 提出了使缠结链结晶的多步骤过程，从而形成中间相。因此，我们打算利用全原子模拟来解决相变问题来处理这种特殊的行为。因此，该提案旨在解决的核心问题是：结晶线是否可以通过全原子模拟实现？ 为了解决这个问题，我们提出了两个轴：1）改进用于揭示熔线的建模系统； 2) 根据轴 1 中讨论的程序，建立从熔融系统中获取晶体的程序。同时，对中间相（根据 Strobl 模型的结晶成分）和玻璃化转变进行研究，与半结晶的研究密切相关聚合物，继续。因此，在研究模拟结晶线的过程中，我们声称有关熔化、结晶、中间相、玻璃化转变的广泛研究将受到影响。该提案最终可以解决的一个典型问题是：熔化温度和玻璃化转变温度之间的经验联系是否合理，该比率通常在 1.2 和 1.3 之间。总之，该提案中利用的这种实验模拟方法越来越被认为是第三种科学研究方式。因此，它非常具有创新性，并为 HQP 提供多学科培训，而 HQP 在当今就业市场中扮演着至关重要的角色。