CAREER: Towards Rational Design of "Smart" Surfaces from Two-Component Polymer Brushes

Colorado State University, Fort Collins CO

Investigators

Abstract

0847016 Wang A nanotechnology-related project is supported to understand and predict the response of two-component polymer brushes, particularly the polyelectrolyte (PE) brushes, to various external stimuli (solvent selectivity, solution pH, ionic strength, and applied electric field) and the influence on such response by various design factors (chain architecture, polymer/block lengths and charges, grafting densities, and incompatibility between the two components). The seemingly simple two-component brushes (including both binary homopolymer brushes and block copolymer brushes) can exhibit a rich variety of interesting and novel behavior through self-assembly of the two components, and have diverse applications in many fields as smart surfaces. The design of these responsive brushes for practical applications such as chemical gates, sensors, biomaterials, and drug delivery, however, requires detailed understanding of the physics of their stimuli-response and knowledge of how various design parameters affect their stimuli-response, which are currently rather limited. Coarse-grained models describing the generic features of two-component brushes will be used, and two judiciously designed and complementary methods, 3D parallel self-consistent field (SCF) calculations and novel fast off-lattice Monte Carlo (FOMC) simulations, will be employed. The computational results will be validated by experiments through collaborations to ensure that they capture the physics of stimuli-response of two-component brushes and can provide essential guidance to experimental design of such smart surfaces. Intellectual Merit: The overall goal of the PI's research is to understand and predict the behavior of inhomogeneous systems of polymers at surfaces and interfaces using advanced theories and simulation techniques. The project will greatly advance current understanding and predictive capability on the stimuli-response of two-component polymer brushes and enable knowledge-based rational design of such smart surfaces best suited for targeted applications, while avoiding both labor and time intensive trial and error experiments. The fundamental knowledge discovered in this work can also be transferred to other inhomogeneous polymeric systems. For example, understanding the effects of correlations and fluctuations revealed in PE brushes here is of fundamental importance in polymer science, and is the prerequisite for developing more accurate theories for PE systems. Finally, the computational tools developed in this project could be readily extended to a wide variety of inhomogeneous polymeric systems that have great potential applications in nanotechnology. In particular, applying FOMC simulations in the study of soft materials is potentially transformative and may revolutionize the computational study of these systems. Broader Impacts: The project will advance current understanding and predictive capability on the stimuli response of two-component polymer nano-scale brushes and enable knowledge based rational design of such smart surfaces best suited for targeted applications (e.g., bio-medical devices), while avoiding both labor and time intensive trial and error experiments. The proposed interdisciplinary work well integrates research activities into the teaching of science and engineering, not only for graduate and undergraduate students, but also for high school students and science teachers, as well as the general public. Some of the computational results will be transformed into movies and made available to the general public. These movies will show the concept, switching mechanisms and stimuli-response of the smart surfaces, with specific examples chosen from the broad applications of smart surfaces to demonstrate the potential applications of the research and anticipated societal benefits. Through the movie making process, the students can much better relate their theoretical and computational research to reality. The simulation movies will be provided to the teachers, who can then play in their classrooms. Given the wide applications of smart surfaces in many fields, this will introduce to high school students through direct visualization the broad scope of Chemical and Biological Engineering profession and the societal benefits that the proposed research has, and stimulate the interest and passion of a large number of high school students on scientific and engineering research. Examples from the proposed work will also be incorporated into a new graduate level course, Advanced Computational Methods for Materials, being developed by the PI, which greatly promotes the application of various computational tools in nanoscience and nanotechnology. This proposal is also synergistic with Colorado aggressive efforts to lead in nanotechnology research and development and formation of the Colorado Nanotechnology Initiative integrated with higher education in Colorado.