CAREER: Probing Crystal Nucleation in Soft Confinement with Molecular Simulation

控制液体中的结晶成核在与药物加工和材料设计相关的应用中具有重要意义。晶体生长可以通过微调分子水平上成核的局部环境来控制到所需的大小、形状和结构。该项目的目标是了解受软水凝胶基质限制的液体中的结晶成核。基质中的约束几何形状和化学成分可能会改变成核途径和由此产生的结晶。先进的分子模拟技术将被用来发现软水凝胶基质影响晶体成核的机制。该项目的教育部分包括开发一个新的短期课程和针对休斯敦地区K-12学生的推广活动。将通过部署罕见事件分子模拟技术来测试总体假设，以解决三个具体目标：(1)阐明软水凝胶基质影响冰核形成热力学的机制；(2)确定软限制对水凝胶中水的结晶动力学的影响；(3)探索具有可调结构的聚合物刷子中碳酸钙沉淀的途径。自由能方法将用于计算成核势垒和识别亚稳态中间体，而路径采样算法将用于表征结晶动力学和机理。这一技术的结合将揭示基质性质(密度、表面化学和形态)对成核的影响，从而改变对软基质中控制结晶的物理过程的理解。将开发一门以科学可再生性为重点的课程--可复制科学的艺术，并将向休斯顿大学的研究生和本科生教授这门课程，并通过在线视频教程广泛传播。将开展推广活动，通过参加莱梅尔森-麻省理工学院合资企业InvenTeams年度计划、针对女性和代表性不足的少数族裔的年级暑期计划、德克萨斯州软物质会议和西南催化学会会议，为K-12学生提供机会了解研究和STEM职业道路。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Controlling crystal nucleation in liquids is important in applications related to pharmaceutical processing and designing materials. Crystal growth can be controlled to desired size, shape, and structure by fine tuning of the local environment in which nucleation takes place at the molecular level. The goal of this project is to understand crystal nucleation in liquids confined by soft hydrogel matrices. The confinement geometry and chemistry within the matrices may alter nucleation pathways and resulting crystallization. Advanced molecular simulation techniques will be used to discover the mechanisms by which soft hydrogel matrices influence crystal nucleation. The educational part of this project includes the development of a new short course and outreach activities to K-12 students in the Houston area.The overarching hypothesis will be tested by deploying rare-event molecular simulation techniques to address three specific aims: (1) to elucidate the mechanisms by which soft hydrogel matrices influence ice nucleation thermodynamics; (2) to identify the effects of soft confinement on the crystallization kinetics of water in hydrogels; (3) to probe the pathways for calcium carbonate precipitation in polymer brushes with tunable architectures. Free energy methods will be used to compute nucleation barriers and identify metastable intermediates, while path sampling algorithms will be employed to characterize crystallization kinetics and mechanisms. This combination of techniques will reveal the effects of matrix properties (density, surface chemistry, and morphology) on nucleation and thereby transform understanding of the physical processes controlling crystallization in soft matrices. A course focusing on reproducibility in science will be developed, The Art of Reproducible Science, and will be taught to graduate and undergraduate students at the University of Houston and broadly disseminated through online video tutorials. Outreach activities will be developed to provide K-12 students with opportunities to learn about research and STEM career paths through participation in the annual Lemelson-MIT JV InvenTeams program, GRADE summer program for women and underrepresented minorities, Texas Soft Matter Meeting, and Southwest Catalysis Society Meeting.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.