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

近年来，随着新的实验发现的出现和/或对现有理论的重新审视，聚合物熔融和结晶的基础经历了深刻的变化，导致对这些现象的潜在机制的重新考虑。更好地把握这一问题已成为当务之急，因为预计不仅在基础科学方面会产生影响，而且在技术应用方面也会产生影响，这一联系在加拿大越来越受到重视。我们希望这项提议带来的新视角解决了这个问题，这要归功于一种新的方法来研究相变，如玻璃、旋节以及中间相和纳米晶体的熔化转变。我们的方法依赖于使用全原子模拟方法。*报告了实验中的熔化温度、结晶温度和结晶温度，温度与晶片厚度成反比，导致两条直线，但斜率不同。因此，有一个有限厚度的交点，导致一个意想不到的结果，其中T_c变得高于T_m。为了证明这一结果是合理的，有人认为晶体的发育分为两个步骤。首先形成微晶，然后变成片状微晶。Strobl提出了缠结链结晶的多步骤过程，导致了中间相的形成。因此，我们打算利用全原子模拟来解决相变问题，以处理这种特殊的行为。这项提议旨在解决的核心问题是：结晶线可以通过全原子模拟实现吗？为了解决这个问题，我们提出了两个轴：1)改进用于揭示熔融线的模拟系统；2)建立一个程序，根据轴1中讨论的程序从系统熔体中提取晶体。同时，对中间相的研究继续进行，根据Strobl的模型，中间相是结晶的组成部分，玻璃化转变与半结晶聚合物的研究密切相关。因此，在从模拟中研究晶化线的同时，我们声称，关于熔化、结晶、中间相、玻璃化转变的广泛研究将受到影响。这项提议最终可以解决的一个典型问题是：熔化和玻璃化转变温度之间的经验联系是否有正当理由，这一比率通常在1.2到1.3之间。总而言之，在这项提议中采用的这种模拟的实验方法，越来越被认为是做科学的第三种方式。因此，它是非常创新的，并为HQP提供多学科培训，这在当今就业市场上是一个至关重要的角色。

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.