Ab initio entangled polymer rheology: homopolymers, blends and copolymers

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PI: Schieber, Jay D. Proposal Number: 1438700Institution: Illinois Institute of TechnologyThe focus of this project is on investigating entangled polymer rheology with a multiscale computationally approach. The proposed research will pin down the parameters needed to be calculated at the atomistic level, in order to provide macroscopic scale predictions about the rheology of a wide class of soft materials. Entangled polymers have tremendous economic impact in industrial materials, and also influence the mechanics of biological tissue. Any significant advance in the understanding of these dynamics will have substantial impact on many branches of physics, materials science, biophysics, biology and engineering. The co-PIs will produce a user-friendly graphical user interface (GUI) and make their GPU code available for public consumption. This code would allow any user with a simple desktop and graphics card (less than $1k) to predict the linear or nonlinear rheology of any blend of linear, branched or cross-linked entangled homopolymers in a homogeneous flow field.It is proposed to achieve the first ab initio dynamic prediction for soft matter that exhibits relaxation times of seconds or minutes. A hierarchical structure of simulations is proposed, starting from ab initio type of calculations. The goal is to make predictions possible for any entangled homopolymer chain architecture, any molecular weight, any blend of architecture and molecular weight, and for any flow field. The homopolymer model to be used is thermodynamically based and in accordance to mean-field theory. While currently available models require parameter fitting and empiricisms, the intellectual achievement of this work, if successful, is to predict the rheology of entangled homopolymers from atomistic knowledge only, without any parameter fitting. This feat can be accomplished with the use of techniques to speed-up calculations by about 12 orders of magnitude, allowing the bridging of the time scales between atomistic and macroscale times.