Molecular Dynamics Simulations for the Prediction of the Conformational, Dynamic, and Thermal Properties of Poly(phenylsulfone) (PPSU) and Their Dependence on Molecular Weight

Abstract

Atomistic configurations of model poly(phenylsulfone) (PPSU) systems, with molecular lengths ranging from N = 5 to N = 50 monomers, were thoroughly relaxed by subjecting them to detailed molecular dynamics (MD) simulations. We present results for their thermal properties, including the thermal expansion coefficient (a_P) and the thermal conductivity (λ). Our simulation predictions for both properties align relatively closely with experimental values, and no significant correlation with the PPSU chain length was recorded. Prior to examining the thermal properties at T = 300 K, we conducted an extensive analysis of the thermodynamic, structural, conformational, and dynamic properties of these models in the molten state at T = 700 K. This provided valuable microscopic insights, such as the dependence of the mean-squared radius of gyration, mean-squared end-to-end distance, self-diffusion coefficient, and total relaxation time on molecular weight, which were subsequently correlated with the zero-rate shear viscosity. During the quenching process from high temperatures to ambient conditions, we estimated the glass transition temperature (T_g) of all model systems, and the predicted values relatively matched the experimental data within the expected range, considering the high cooling rates in the MD simulations. Our simulations effectively captured the important dependence of T_g on molecular weight.