Thermodynamics, Nanostructures, and Transport Properties of Confined Colloid-Polymer Mixtures

这个项目涉及与受限胶体-聚合物混合物(单层和通道)的平衡和传输特性相关的几个具有挑战性的子项目的研究。首先，PI将用Langmuir-Blodgett方法实验研究胶体/聚合物混合物的单分子膜的相行为。这些单分子膜的纳米结构将通过原子力显微镜和布鲁斯特角显微镜来确定。其次，将在McMillan模型的基础上发展一个理论模型来理解这些系统的相变。最后，等电点将通过荧光显微镜来确定聚合物在通道中的扩散以及一对聚合物在受限于狭窄通道的胶体悬浮液中的扩散。在胶体-聚合物混合物的单分子层研究中，将发展一种理论来描述聚合物可能的液晶有序性的结构，并将使用从拟议的实验中获得的证据来检验该理论模型。如果理论与实验不一致，将对理论进行修正，实验参数将在我们的理论中实现。将对聚合物在通道中动力学的实验研究进行详细的研究。测量分辨率和不确定度量化是增强视频荧光显微镜的测量分辨率和不确定度。研究一维聚合物扩散的理论和实验之间的联系。一维通道中胶体存在时的聚合物扩散理论在我们之前的NSF拨款中得到了发展，扩散系数用聚合物的分子参数、胶体的大小和溶剂的粘度来表示。由于这些量是可以直接测量的，我们的实验将直接与理论联系在一起。我们将研究的问题是具有挑战性的基本问题，需要热力学、统计热力学、理论和实验物理化学以及凝聚态物理方面的专业知识。特别是，胶体-聚合物混合物的Langmuir-Blodgett单分子膜的实验研究将确定它们的相变，并揭示与受限几何中的耗尽效应有关的未解决问题。拟议的活动本质上是基本的，但它是受提议中描述的涉及纳米粒子以及胶体和聚合物混合物的自组装的众多技术应用的启发和有益的。这些不同领域所需的专业知识使其成为一项跨学科研究，通常不是由单一的专业人员进行的。拟议活动产生的广泛影响除了国际和平研究所的研究生(其中几人已成为一流大学的教授)外，许多本科生将参加拟议的活动，一些人将在国家和地区科学会议上发言并成为出版物的合著者，就像以前的国家科学基金会拨款一样。事实证明，这种融合和鼓励非常有效地促使PI的本科生，包括许多女性，决定进入化学工程和相关学科的研究生院学习。这位莱斯大学最优秀的本科二年级学生是一名女性，她已经表达了加入这个团体的兴趣。PI将继续参与莱斯大学的几个外展项目，在这些项目中，他以可以理解的方式与休斯顿以非裔美国人和西语裔为主的公立学校的初中和高中教师和学生讨论这项拟议的活动，这些学校在学术界的代表性最低。PI将继续努力让他们相信科学进步和社会进步之间的密切联系。PI还将维持对他的实验室的暑期访问，在一周的时间里，几名中学生在暑期参加研究。

1034421RobertThis project involves the study of several challenging sub-projects related to the equilibrium and transport properties of confined colloid-polymer mixtures (monolayers and channels). First, the PI will investigate experimentally by the Langmuir-Blodgett method the phase behavior of monolayers of colloid/polymer mixtures. The nanostructures of these monolayers will be determined by atomic force microscopy and Brewster angle microscopy. Secondly, a theoretical model will be developed based on that of McMillan to understand the phase transitions of these systems. Lastly, the PI will determine by florescence light microscopy the diffusion of polymer in channels as well as the diffusion of a pair of polymers in colloidal suspensions confined to narrow channels. Intellectual Merit of the Proposed Activity In the investigations of monolayers of colloid-polymer mixtures, a theory will be developed in order to describe the structure of the possible liquid-crystalline ordering of the polymers and the evidence garnered from the proposed experiments will be used to test the theoretical model. The theory will be modified if it fails to agree with the experiments, and the experimental parameters will be implemented in our theory. The details of experimental study of dynamics of polymer in channels will be investigated. The measurement resolution and uncertainty quantification are those of enhanced video fluorescent microscopy. The connection between theory and experiment for one-dimensional polymer diffusion will be studied. The theory of polymer diffusion in the presence of colloids in one-dimensional channels was developed in our previous NSF grant, and the coefficient of diffusivity was expressed in terms of the molecular parameters of the polymer, the size of the colloids, and the viscosity of the solvent. Since these quantities are directly measurable, our experiments will be directly connected to theory.The problems that will be studied are challenging fundamental ones which require expertise in thermodynamics, statistical thermodynamics, theoretical and experimental physical chemistry and condensed matter physics. In particular, the experimental investigations of Langmuir-Blodgett monolayers of colloid-polymer mixtures will determine their phase transitions and shed light on unsolved problems related to depletion effects in confined geometries. The proposed activity is fundamental in nature, but it is inspired by and is beneficial to the numerous technological applications which involve self-assemblies of nano-particles and mixtures of colloids and polymers which are described in the proposal. These diverse fields of expertise required make it an interdisciplinary study not usually carried out by a single PI. Broader Impacts Resulting from the Proposed Activity In addition to the PI's graduate students, several of which have become professors at first-rate universities, a large number of undergraduate students will take part in the proposed activity, and several will make presentations at national and regional scientific meetings and become coauthors of publications, as has been the case under the previous NSF grant. Such integration and encouragement proves very effective in making undergraduate students of the PI, including many women, decide to go to graduate school in chemical engineering and in allied disciplines. The top undergraduate sophomore student at Rice University, a woman, has already expressed her interest in joining the group. The PI will continue to be involved in several outreach programs of Rice University, in which he discusses this proposed activity in understandable terms with middle and high school teachers and students, in predominantly African-American and Hispanic public schools of Houston, those most largely underrepresented in academia. The PI will pursue his efforts to convince them of the intimate bond between scientific and societal progress. The PI will also maintain the summer visits to his laboratory in which, during one week, several middle school students in the summer take part in research.