Dissipative particle dynamics simulation of microphase separation in polyurethane urea nanocomposites

YR Sliozberg and JL Gair and AJ Hsieh, POLYMER, 193, 122339 (2020).

DOI: 10.1016/j.polymer.2020.122339

Vertically aligned carbon nanotube reinforced segmented poly(urethane- urea) (PUU) polymer nanocomposites (A-CNT/PUU PNCs) have been synthesized and proven to be potential candidates for novel materials with high mechanical strength, toughness, and thermal energy dissipation. It has been experimentally observed that incorporation of A-CNTs could induce interface-mediated nanophases of PUU along the A-CNTs axes. Here, we employed dissipative particle dynamics (DPD) computer simulations to elucidate the nature of the filler and matrix relationship in polyurethane composites at a molecular level. Diamine and diisocyante, the constituents of hard segments (domains), were found to have a propensity to adsorb onto the CNTs. This phenomenon is presumably facilitated by their greater thermodynamic compatibility with CNTs than the soft segments. Additionally, increasing the polymer's effective density leads to a rise in thermodynamic incompatibility of the polymer blocks. Hard domain aggregation around the CNTs' axes and between CNTs was also found to increase the conformational entropy. At the higher CNT loading, when the inter-CNT spacing becomes comparable with the distance between hard domain clusters, these domains form nanophase columns. Finally, simulation results agree with our previous PUU experimental data.

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