Theory and Computer Simulations of Polyampholyte-Polyelectrolyte Complexes

该奖项支持理论和计算研究和教育，旨在开发含有聚两性离子-聚电解质络合物的溶液的分子水平模型。当聚电解质与相同净电荷的聚两性阳离子(蛋白质)混合时，形成可溶的络合物。这种结合发生的方式是，蛋白质上相反带电的氨基酸靠近聚电解质，导致两者之间的静电吸引。由于聚两性阳离子的大量过剩，每个聚电解质链都被聚两性阳离子饱和，溶液为液体。随着聚电解质加入量的增加，粘度逐渐增大。一旦加入足够的聚电解质，就会形成一种可逆凝胶，其中一些聚两性离子分子作为聚电解质链之间的临时交联剂。这项研究旨在建立分子模型，描述在广泛的聚合物和盐浓度、溶液pH以及聚合物的各种性质，如其相对分子质量和电荷分布等情况下，聚两性离子-聚电解质络合物的形成。在稀溶液中，由此得到的模型将提供聚两性离子-聚电解质络合物的内部结构以及反离子释放和缩合对络合物形成的影响的细节。在半稀溶液中将研究络合缔合和可逆凝胶的形成。这将允许预测聚合物构象和溶液性质，如粘度、扩散系数和松弛时间。理论模型的假设将通过计算机模拟进行验证。将渗透系数、扩散系数、线粘弹性和稳态剪切粘度的计算结果与实验结果进行了比较。即将开发的聚两性离子-聚电解质复合体的分子模型可能会在生物医学领域以及利用带电大分子作为流变学调节剂的领域产生深远的影响。例如，蛋白质-聚电解质复合体控制滑液的流变性和润滑性。蛋白质-聚电解质复合体的一个实际工业用途是使用聚电解质来提高用于涂布照相胶片和纸张的蛋白质溶液的粘度。在这两种情况下，蛋白质和聚电解质之间的相互作用直接控制着复合体的流变性。拟议的项目非常适合对本科生和研究生进行现代分析和数值技术方面的培训，并将辅导融入拟议研究的各个方面。研究生将与物理、化学或化学工程的本科生合作，这些学生将通过独立研究获得学分或通过本科生研究经验(REU)计划参与其中。拟议的研究结果将被纳入聚合物物理、聚合物物理化学的课程序列，以及新的专题课程带电高分子。该奖项支持理论和计算研究和教育，旨在开发含有带电聚合物、聚两性离子-聚电解质络合物的溶液的分子水平模型。当聚电解质(例如聚丙烯酸)与相同净电荷的聚两性阳离子(例如蛋白质)混合时，形成可溶的络合物。蛋白质上的相反电荷的氨基酸与聚电解质结合在一起，造成两者之间的静电吸引。由于聚两性阳离子的大量过剩，溶液是液体。随着聚电解质加入量的增加，粘度逐渐增大。一旦加入足够多的聚电解质，就会形成可逆凝胶。这项研究的目的是开发分子模型，描述在广泛的条件下聚两性离子-聚电解质络合物的形成。在稀溶液中，所得到的模型将能够预测聚合物的构象，以及各种溶液性质，如粘度、扩散系数和松弛时间。理论模型的假设将通过计算机模拟进行验证，对各种性质的预测将与实验进行比较。即将开发的聚两性离子-聚电解质复合体的分子模型可能会在生物医学领域以及利用带电大分子作为流变学调节剂的领域产生深远的影响。例如，蛋白质-聚电解质复合体控制滑液的流变性和润滑性。蛋白质-聚电解质复合体的一个实际工业用途是使用聚电解质来提高用于涂布照相胶片和纸张的蛋白质溶液的粘度。在这两种情况下，蛋白质和聚电解质之间的缔合直接控制着复合体的流变性。拟议的项目非常适合对本科生和研究生进行现代分析和数值技术方面的培训，并将辅导融入拟议研究的各个方面。研究生将与物理、化学或化学工程的本科生合作，这些学生将通过独立研究获得学分或通过本科生研究经验(REU)计划参与其中。拟议的研究结果将被纳入聚合物物理、聚合物物理化学的课程序列，以及新的专题课程带电高分子。***

This award supports theoretical and computational research and education with an aim to develop molecular level models of solutions containing polyampholyte-polyelectrolyte complexes. When a polyelectrolyte is mixed with a polyampholyte (protein) of the same net charge, a soluble complex is formed. The binding occurs in such a way that the oppositely charged amino acids on the protein are close to the polyelectrolyte, causing an electrostatic attraction between the two. With a large excess of polyampholyte, each polyelectrolyte chain is saturated with polyampholytes and the solution is a liquid. As more polyelectrolyte is added, the viscosity steadily increases. Once, enough polyelectrolyte is added, a reversible gel is formed with some polyampholyte molecules acting as temporary crosslinks between polyelectrolyte chains. The research aims to develop molecular models describing the formation of polyampholyte-polyelectrolyte complexes in a wide range of polymer and salt concentrations, solution pH and various properties of polymers like their molecular weight and charge distribution. In dilute solutions the resulting model will provide details of the internal structure of polyampholyte-polyelectrolyte complexes and of the effects of counterion release and condensation on the complex formation. The formation of intercomplex associations and reversible gelation will be studied in semidilute solutions. This will allow prediction of polymer conformations, and solution properties such as viscosity, diffusion coefficient, and relaxation time. The assumptions of the theoretical models will be tested by computer simulation. The results for osmotic coefficient, diffusion coefficient, linear viscoelasticity and steady shear viscosity will be compared with experiments. The molecular models of polyampholyte-polyelectrolyte complexes that will be developed may have far-reaching consequences in the bio-medical area, and in areas utilizing charged macromolecules as rheology modifiers. For example, protein-polyelectrolyte complexes control the rheology and lubrication properties of synovial fluid. A pragmatic industrial use of protein-polyelectrolyte complexes is to use polyelectrolytes to boost the viscosity of protein solution for coating photographic film and paper. In both cases, the associations between the protein and the polyelectrolyte directly control rheology of the complex. The proposed project is well suited for training undergraduate and graduate students in modern analytical and numerical techniques and mentoring is integrated into every aspect of the proposed research. Graduate students will work with undergraduate physics, chemistry or chemical engineering students who will be involved either through independent research for credit or through Research Experience for Undergraduates (REU) programs. The results of the proposed research will be incorporated into a course sequence on Polymer Physics, Polymer Physical Chemistry, as well as into new special topics course, Charged Macromolecules. %%%This award supports theoretical and computational research and education with an aim to develop molecular level models of solutions containing charged polymers, polyampholyte-polyelectrolyte complexes. When a polyelectrolyte (e.g. polyacrylic acid) is mixed with a polyampholyte (e.g. a protein) of the same net charge, a soluble complex is formed. The oppositely charged amino acids on the protein are bound close to the polyelectrolyte, causing an electrostatic attraction between the two. With a large excess of polyampholyte, the solution is a liquid. As more polyelectrolyte is added, the viscosity steadily increases. Once, enough polyelectrolyte is added, a reversible gel is formed. The research aims to develop molecular models describing the formation of polyampholyte-polyelectrolyte complexes under a wide range of conditions. In dilute solutions the resulting model will enable the prediction of polymer conformations, and various solution properties such as viscosity, diffusion coefficient, and relaxation time. The assumptions of the theoretical models will be tested by computer simulation and predictions for various properties will be compared with experiments. The molecular models of polyampholyte-polyelectrolyte complexes that will be developed may have far-reaching consequences in the bio-medical area, and in areas utilizing charged macromolecules as rheology modifiers. For example, protein-polyelectrolyte complexes control the rheology and lubrication properties of synovial fluid. A pragmatic industrial use of protein-polyelectrolyte complexes is to use polyelectrolytes to boost the viscosity of protein solution for coating photographic film and paper. In both cases, the associations between the protein and the polyelectrolyte directly control the rheology of the complex. The proposed project is well suited for training undergraduate and graduate students in modern analytical and numerical techniques and mentoring is integrated into every aspect of the proposed research. Graduate students will work with undergraduate physics, chemistry or chemical engineering students who will be involved either through independent research for credit or through Research Experience for Undergraduates (REU) programs. The results of the proposed research will be incorporated into a course sequence on Polymer Physics, Polymer Physical Chemistry, as well as into new special topics course, Charged Macromolecules. ***