NSF-DFG Confine: MolPEC – Molecular Theory of Weak Polyelectrolytes in Confined Space

在这个由化学系化学理论、模型和计算方法项目（CTMC）支持的项目中，加州大学河滨分校的吴建中教授正在开发描述一类被称为弱聚电解质（WPE）的聚合物的理论模型。 这是一个与德国乔治-奥古斯特-哥廷根大学的研究人员合作的项目。WPE是一大类大分子，其可以质子化或去质子化，这取决于环境条件如pH和盐浓度。它们的刺激响应行为已被广泛用于功能性“智能”材料，用于靶向药物递送或水下粘附等应用。而实际应用往往需要在空间限制下的化学和物理过程，WPE的结构和动力学仍然不完全理解，由于在单体和聚合物尺度上的反应和聚合物介导的相关性的强耦合。WPE系统的合理设计要求在理论和计算方法上取得进展，这些方法能够准确地描述局部溶液环境，质子化/去质子化平衡以及聚合物与可电离表面反应的动力学的限制效应。本研究的目的是建立一个理论框架，用于描述受限空间中WPE的特性及其对环境条件的响应，包括溶液pH值，电解质成分和限制化学。我们将利用这些技术来研究离子大小，价态，电离，表面反应和聚合物结合的动力学，不能可靠地解决与传统方法之间的相互作用。理论和计算的进步将有助于为广泛的技术应用合理设计弱耦合系统。基于聚合物密度泛函理论（PDFT）和分子模拟的互补进展，美国-德国团队将研究弱聚电解质在表面和表面之间的结构，热力学和动力学。其思想是联合收割机和扩展伊辛密度泛函理论（iDFT）和单链平均场（SCMF）模拟。iDFT考虑单链构型和链段的电离状态，并通过分子密度捕获液体状堆积和静电相关性。整个大分子的构型和电离态的联合概率分布由单链势决定，而单链势又是分子密度的函数。高维分子密度将有效地评估通过SCMF模拟并行，GPU加速的超级计算机，采用iDFT单链势。该团队将扩展模拟代码，软粗粒度蒙特-卡罗加速（索马），将静电相互作用和非局部相互作用沿着分子轮廓。基于粒子的模拟，动态iDFT（D-iDFT），占长程波动，并允许我们研究的配置动力学。此外，我们将推导出一个基于段的动态iDFT（SD-iDFT），用于描述响应于环境变化的局部聚合物质量和电荷密度。在这项工作中提出的理论技术的通用性，确保广泛的应用，以不同的现象在聚合物和生物系统。 本项目将为早期职业科学家提供培训机会，以获得跨学科的研究经验，并培养他们对计算分子工程的职业兴趣。除了支持研究生，它还为现役军人，退伍军人和大学荣誉计划（UHP）的学生提供基于研究的论文项目。 该项目通过“受限空间中的化学和运输（NSF-DFG Confine）”机会授予，这是一个涉及美国国家科学基金会和德国研究共同体（DFG）的合作招标。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

In this project supported by the Chemical Theory, Models and Computational Methods Program (CTMC) of the Division of Chemistry, Professor Jianzhong Wu of the University of California-Riverside is developing theoretical models that describe a class of polymers known as weak polyelectrolytes (WPEs). This is a collaborative project with researchers from the Georg-August-Universität Göttingen, Germany. WPEs are a large class of macromolecules that may either protonate or deprotonate depending upon the environmental conditions such as pH and salt concentration. Their stimuli-responsive behavior has been broadly utilized in functional “smart” materials for applications such as targeted drug delivery or underwater adhesion. Whereas practical applications often entail chemical and physical processes under spatial confinement, the structure and dynamics of WPEs remain incompletely understood due to the strong coupling of reaction and polymer-mediated correlations at both monomer and polymer scales. The rational design of WPE systems is calling for advances in theoretical and computational methods that are able to accurately describe confinement effects on local solution environment, protonation/deprotonation equilibrium, and the dynamics of polymers reacting with ionizable surfaces. This research aims to develop a theoretical framework for describing the properties of WPEs in confined space and their responses to environmental conditions including solution pH, electrolyte composition, and the chemistry of confinement. We will utilize these techniques to investigate the interplay between ionic size, valence, ionization, surface reactions and the dynamics of polymer binding that cannot be reliably addressed with conventional methods. The theoretical and computational advances will contribute to a rational design of weak polyelectrolyte systems for a wide spectrum of technological applications. Building on complementary advances in polymer density functional theory (PDFT) and molecular simulation, the US-German team will study the structure, thermodynamics, and dynamics of weak polyelectrolytes at and between surfaces. The idea is to combine and extend Ising Density Functional Theory (iDFT) and Single-Chain-in-Mean-Field (SCMF) simulation. iDFT considers single-chain configurations and ionization states of segments on equal footing and captures liquid-like packing and electrostatic correlations via the molecular density. The joint probability distribution of configurations and ionization states of an entire macromolecule is dictated by a single-chain potential, which, in turn, is a functional of the molecular density. The high-dimensional molecular density will be efficiently evaluated via SCMF simulation on parallel, GPU-accelerated supercomputers, employing the iDFT single-chain potential. The team will extend the simulation code, SOft coarse-grained Monte-carlo Acceleration (SOMA), to incorporate electrostatic interactions and nonlocal interactions along the molecular contour. The particle-based simulation, Dynamic-iDFT (D-iDFT), accounts for long-range fluctuations and allows us to study the configuration dynamics. Additionally, we will derive a segment-based dynamic iDFT (SD-iDFT) for describing the local polymer mass and charge density in response to environmental changes. The generic nature of the theoretical techniques proposed in this work ensures broad applications to diverse phenomena in polymeric and biological systems. This project will provide training opportunities for early career scientists to gain interdisciplinary research experience and cultivate their career interests in computational molecular engineering. In addition to supporting graduate students, it offers research-based thesis projects for undergrads in active military service, veterans, and students from the University Honors Program (UHP). This project is being awarded through the “Chemistry and Transport in Confined Spaces (NSF-DFG Confine)" opportunity, a collaborative solicitation that involves the National Science Foundation and Deutsche Forschungsgemeinschaft (DFG).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.