Many modern applications of macromolecular fluids take advantage of their novel microstructure and phase behavior. The challenge in modeling nano-structured fluids lies in understanding the new physics that emerges from finite-size effects, varying dimensionality, surface forces and interplay of multiple length and time scales. The introduction of external surface forces and the competition between fluid substrate and fluid-fluid interactions lead to interesting surface driven phase changes not seen in bulk systems [9].
Intellectual Merit: The project focuses on the to development of a novel molecular theory for multi-scale modeling of complex fluid assemblies and to apply the theory to several critical problems in nano-structured media. The work builds on the PIs new density functional theory (DFT) that has shown an unprecedented combination of accuracy and simplicity in predicting the structure of inhomogeneous polyatomic mixtures [29,30]. Predictions of the DFT are in excellent agreement with molecular simulation results for phenomena such as polymer depletion, enhancement and surface induced segregation key elements in polymer-colloid systems and in coatings of polymer blends. Further, the DFT has similar simplicity and computational speed to an atomic density functional theory. We propose to incorporate multiple molecular association sites, chain stiffness, and hydrophilic and hydrophobic surfaces in the theory. The approach will be validated with molecular simulation results and compared with experiment for interfacial properties and structure of copolymer, surfactant, and tethered polymer systems.
Broader Impact: The immense potential of the DFT has led to an ongoing collaboration with Sandia National Laboratories (SNL) to incorporate our DFT within their massively parallel DFT solver package ? TRAMONTO. With its existing capabilities, TRAMONTO can address life-scale systems such as colloids and electrolytes in a range of 2D/3D geometries. Integrating the PIs polyatomic DFT within this platform dramatically expands the potential scope of the package to such systems as self-assembly in polymer-colloid polymer-nanoparticle systems, block copolymer films and blends, surfactant or lipid systems exhibiting micellar or bilayer structures, and polyelectrolytes. When the final version is released to the public, it is anticipated that these computational tools will have high impact on nanoscience and design of nanosystems by allowing exhaustive analysis of design or phase space (needed for design of experiments) at a moderate expense. Dow Chemical has significant interest in applying the theory to model microstructure and interfacial properties of copolymer solutions, blends, and surfactants. Letters of collaboration from Sandia and Dow are attached with direct and in-kind funding from Dow. Of further impact will be education of a graduate student, post-doc, and undergraduate students participating in the project. These students will make presentations to companies that have participated in our Consortium on Complex Fluids and present research results at international conferences. The graduate student benefited from a summer internship offered by Dow. In addition to incorporating new theory in courses at Rice, the project will develop an educational module (book chapter) of the theory for web distribution using the internationally recognized Connexions environment (cnx.rice.edu).
