A Simulation Study of Entropic and Enthalpic Effects on Local Dispersed Morphologies of Carbon-based Nanofillers in Thermoplastic Polyurethane Matrix

Carbon-based nanofillers (CNs) are widely applied to improve the engineering properties of polymer materials. The dispersion of CNs dominates the uniformity of micro-structures which is crucial to the enhancement of macroscopic properties. Herein, a simulation technique of modified Dissipative Particle Dynamics (DPD) is employed to study the effects of chemistry, interactions, and geometric structures on the locally dispersed morphologies of CNs in the Thermoplastic Polyurethane (TPU) matrix. Our findings indicate that 2-D nanosheets of CNs with a stacked initial morphology can be locally dispersed in the TPU matrix with long hard blocks at equilibrium, while they remain stable in the vicinity of short blocks. Through tuning the oxidation degree, it can be inverted to dispersed morphologies. It's observed that CNs are separated by the insertion of TPU hard blocks and repelled further in strongly aggregated hard blocks. Furthermore, the effects of dispersed initial morphologies and varied geometric structures of CNs on the finial morphological dispersions are studied giving rise to enthalpic stability. Our studies theoretically explain the entropic and enthalpic effects on the local dispersion of CNs and can be the guideline for evaluating the properties of TPU-CNs nanocomposites.