Molecular Studies of Phase Transitions in Soft Matter: The Lower Critical Solution Temperature Transition Études moléculaires de transitions de phases dans la matière molle: LCST

在这个为期5年的研究计划中，我们希望利用强大的多尺度方法来研究一个具有重大科学和技术兴趣的主题：热响应性聚合物中的更低临界溶液温度(LCST)。在LCST以上，热响应性聚合物在水溶液中的溶解度降低，导致相分离。由于其特殊的技术和生物医学兴趣，这种现象在过去20年里受到了越来越多的关注。尽管有大量的研究，但许多基本问题仍然没有完全被了解，如从盘绕到球状(CTG)的转变，聚集体的形成及其稳定性，共单体和溶解效应。从概念上讲，相变是一种集体现象。通过准确描述原子相互作用和分子排列来评估协作性长度，将使相变的描述变得无价，并允许揭示分子变化。相变所固有的热力学或平均场模型所固有的普遍特性必须被视为极限。因此，拟议的研究方案旨在通过利用多尺度方法来解决这些重要和根本的问题。这项研究是一个更长期和雄心勃勃的研究计划的一部分：相变的分子研究。这一引人入胜的研究领域揭示了这样一个事实，即已建立的热力学转变在分子水平上并没有得到很好的理解。存在并需要考虑重大问题：离散性与连续性；有限到无限大小的考虑与阿伏加德罗分子数的统计；简约论与浮现；特定的相互作用/涨落与平均场。许多重要的复杂问题都以这样或那样的方式与相变现象的存在有关。癌症可以被认为是相变的开始。

In this 5-year research program, we want to exploit the powerful multi-scale approach to study a topic of great scientific and technological interest: Lower Critical Solution Temperature (LCST) in thermoresponsive polymers. Above the LCST, thermoresponsive polymers in aqueous solution show a decrease in their solubility, resulting in phase separation. Due to its particular technological and biomedical interests, such phenomenon has been increasingly scrutinized over the past two decades. Despite numerous studies, many fundamental questions remain not fully understood such as the transition from coil-to-globule (CTG), the aggregate formation and their stability, the co-monomer and the cononsolvency effects. Conceptually, a phase transition is a collective phenomenon. Evaluating a cooperativity length, through an accurate depiction of atomic interactions, and a fortiori molecular arrangement, will make the description of phase transition invaluable, and allow unveiling molecular changes. The universal character, inherent to thermodynamics, or to the mean-field model, of a phase transition must be considered as a limit. The proposed research program is thus aimed at addressing such important and fundamental questions by exploiting the multi-scale approach. This study is part of a longer and ambitious research program: molecular study of phase transitions. This captivating research domain exposes the fact that well-established thermodynamic transitions are not well understood on the molecular level. Significant issues exist and need to be considered: discreteness versus continuity; finite to infinite size consideration of statistics with Avogadro number of molecules; reductionism versus emergence; specific interactions/fluctuations versus mean-field. Many important problems of complexity are related in one way or another with the presence of phase transition phenomena. Cancer can be considered as the onset of phase transition.