Bond Tension, Surface Structure and Adsorption on Bottle-Brush Tethered Polymer Layers

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NONTECHNICAL SUMMARYThis award supports theoretical and computational research and education aimed at a fundamental understanding of surfaces coated with bottle-brush polymers to add new function to the surface, for example bottle-brush polymers on the cartilage surface covering bone adds lubrication. Bottle-brush polymers have found important applications in coatings and surface treatments, especially for coatings that are resistant to particular proteins or selective to specific proteins, such as for applications requiring selectivity toward certain proteins in biomedical applications and for the filtering or remediation of water by removing such impurities. Polymers are made of molecules that are strung together to form long chain molecules. Bottle-brush molecules feature side chains grafted to a linear backbone at such density that there is a high degree of repulsion between side chains. This repulsion results in tension along the side chain which is transmitted to the backbone which may be harnessed to break bonds within the molecule to create self-modifying behavior. Experimental evaluation of the properties of such structures can be prohibitive in cost and time and the interactions that make such molecules interesting often occur at the molecular level, barely in range of experimental investigation. Computer simulation enables investigations of bottle-brush molecules at different length and time scales to evaluate the properties of given classes of polymers for a specified application. The PI will use computer simulation to advance understanding of the properties of bottle-brush tethered layers and their relationship to the architecture of bottle-brush polymers.This work will fundamentally advance the theory of physical properties of bottle-brush polymers and specifically bottle-brush polymers tethered to surfaces to add new functionality. It will also provide a framework for the development of future theory regarding the physical properties of novel polymer architectures and the effects of architecture in the surface properties of polymer-based coatings, surfaces and surface treatments based on alternative polymer structures. It will aid in the design of new polymer-based materials, systems, and devices based on alternative polymer architectures. As such, this research contributes to the goals of the Materials Genome Initiative. The knowledge gained from the research contributes to the discovery and understanding of emergent effects that result as a consequence of novel architectures, such as tension accumulation and adsorption resistance in bottle-brush polymers. In addition to training and mentoring of undergraduate and graduate students using this award, the new knowledge acquired will be incorporated in graduate level courses.NONTECHNICAL SUMMARYThis award supports theoretical and computational research aimed to advance fundamental understanding of polymer-functionalized surfaces such as polymer bottle-brushes. The concept of self-modification through the use of intermolecular or intramolecular tension within bottle-brush tethered layers is a relatively new one, having been investigated experimentally only in recent years. It has been most often applied to cases in which the detached chains do not remain with the backbone, such as in coatings for drug-delivery applications. In a dense surface layer, however, the detachment and diffusion of side chains or of bottle-brush fragments within the surface layer has not, to our knowledge, been extensively studied either by simulation or experiment. Depending on the density of the brush layer, as well as any present intermolecular interactions between brush components, detachment of side chains may lead to local effects, such as reorientation into small-scale domains or may have global effects, such as plasticization of the brush layer that directly affects the adsorption characteristics and surface structure. Computer simulation enables the investigation of bottle-brush polymers and related systems, at scales ranging from the atomic to the coarse-grained or continuum, to evaluate the properties of given classes of polymers for a specified application. The PI will use coarse-grained molecular dynamics simulation to characterize bottle-brush tethered layers to study the effects of variation in side-chain grafting density, relative backbone/side-chain length, and chemical nature of brush components, for example copolymerization and noncovalent interaction. The PI will use simulation to characterize the surface adsorption characteristics for intact brush layers and layers which allow component detachment (side chains, brush segments), to investigate detachment dynamics and the effect of detached components on the structure and surface characteristics of the brush layer.This work will fundamentally advance the theory of physical properties of bottle-brush polymers and specifically bottle-brush polymers tethered to surfaces to add new functionality. It will also provide a framework for the development of future theory regarding the physical properties of novel polymer architectures and the effects of architecture in the surface properties of polymer-based coatings, surfaces and surface treatments based on alternative polymer structures. It will aid in the design of new polymer-based materials, systems, and devices based on alternative polymer architectures. As such, this research contributes to the goals of the Materials Genome Initiative. The knowledge gained from the research contributes to the discovery and understanding of emergent effects that result as a consequence of novel architectures, such as tension accumulation and adsorption resistance in bottle-brush polymers. In addition to training and mentoring of undergraduate and graduate students using this award, the new knowledge acquired will be incorporated in graduate level courses.