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，聚合物熔融和结晶的基础经历了深刻的转变，因为新的实验发现已经出现和/或重新审视已建立的理论已经提出，导致重新考虑这些现象的潜在机制。 更好地把握这一问题已变得紧迫，因为不仅在基础科学方面，而且在技术应用方面都预计会产生影响，这一联系在加拿大越来越受到重视。 我们希望通过这项建议带来的新观点解决了这一问题，这要归功于一种新的方法来研究相变，如玻璃，亚稳，以及中间相和非晶熔化转变。我们的方法依赖于使用全原子模拟方法。 * 相对于晶体片层厚度的倒数报告实验熔融Tm和结晶Tc温度，得到两条直线，但具有不同的斜率。因此，在有限厚度处存在相交，导致Tc变得高于Tm的意外结果。 为了证明这一结果，有人认为晶体发育分为两个步骤。首先形成微晶，然后转变为层状微晶。Strobl提出了缠结链结晶的多步骤过程，导致形成中间相。因此，我们打算利用全原子模拟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：全原子模拟是否可以实现结晶线？ 为了解决这个问题，我们提出了两个轴：1）改进用于揭示熔化线的模型化系统; 2）根据轴1中讨论的程序建立从系统熔体中获得晶体的程序。同时，对中间相的研究，根据Strobl的模型结晶的一个组成部分，以及与半结晶聚合物的研究密切相关的玻璃化转变，继续进行。因此，在从模拟研究结晶线的基础上，我们声称关于熔融、结晶、中间相、玻璃化转变的广泛研究将受到影响。作为一个典型的问题，这个建议可以最终解决，是：是否有一个合理的熔化和玻璃化转变温度之间的物理联系，该比例通常在1.2和1.3之间。总而言之，这项建议中所采用的模拟实验方法，越来越被认为是从事科学的第三种方式。因此，它是非常创新的，并提供多学科的培训，以HQP，一个至关重要的作用，今天在就业市场。