Integrated multi-scale, multi-tool, modeling of transport in polymer-colloid assemblies

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PI: Larson, RonaldProposal Number: 1602183The goal of the proposed research is to develop predictive methods for coating material properties and to even prescribe these properties by designing materials from the molecular level up. The results of this research would find many applications in engineering and in the industry, since the utility of coating materials in everyday life is unequivocal. Most of the objects around us are coated with a material that either enhances their usefulness or their life time (computer and tablet screens, furniture, metallic objects and tools, walls etc.). While there has been great interest and effort in the area of multi-scale modeling, there have been few, if any, successful predictions of colloidal scale transport properties based on multi-scale modeling starting with atomistic inputs for materials of large-scale commercial interest. Here, it is proposed to integrate a set of methods developed in recent years to allow prediction of the impact of surfactant, polymer, and colloidal composition on the rheological properties of latex coatings. Latex coatings contain surfactant molecules, polymer molecules with hydrophobic "sticker" end groups, and colloidal particles that are bridged by the polymer molecules to form a transient network. The simulation tools to be implemented and integrated are molecular dynamics simulations at the atomistic, coarse-grained (CG) and implicit-solvent CG levels, Brownian dynamics simulations using coarse-grained polymer chains using finitely extensible (FENE) spring models, population balance methods for tracking numbers of bridging polymer chains between pairs of colloidal particles, and Stokesian dynamics methods for computing the hydrodynamic interactions of colloidal particles undergoing shear flow. Also to be exploited are methods of computing free energies of microscopic transitions, such as free energy of transition of a bridging to a looping chain, and free energy of compression of polymer chains bound to colloidal particles. While all of these tools have been developed or exploited in the Larson group over the past decade, and integration of many of the methods has been carried out at the level of thermodynamics, the proposed new research is to map the transport properties of these methods onto each other, so that transport rates determined at the finest levels allow input parameters and time-scales of coarser-grained methods to be specified. The mapping will also be validated and improved upon, through comparison with experimental data. Accomplishment of this project will lead to a set of inter-locking modeling tools that will not only allow prediction of the rheological properties of latex coatings, but will establish a paradigm to be followed for modeling many other complex materials and multi-scale transport processes. Broader impacts include interactions with industry. An outreach to minority students will be undertaken and a Ph.D. student will be recruited and trained both through the work at Michigan and through summer internships at Dow Chemical Company. An open source software package for prediction of the rheological properties of polymer/colloid materials will be developed and international collaborations with Edinburgh University and Durham University at the UK will be established.