Melting of polymer nanocrystals: a comparison between experiments and simulationElectronic supplementary information (ESI) available: DSC traces. See DOI: 10.1039/c1sm06446k

Polymer nanocrystals have attracted considerable attention because of their potential applications in future technology and their fascinating properties which differ from those of corresponding bulk materials. The essential influence of the nanointerface in nanocrystals is apparent in the linear dependence of the melting temperature with the inverse sheet thickness, i.e. the GibbsThomson behaviour. Yet, few experimental and theoretical works have been attempted to highlight the influence of nanointerfaces on the thermal properties of nanocrystals. In this work, simulations were used to evaluate the melting temperature of crystalline polymer nanosheets. Ensuing results were compared favourably to experimental melting temperatures stemming from alkane chains and functional polyolefins, thus validating our simulation approach. Both experimental and simulated results followed GibbsThomson behaviour and a procedure was devised to extract the heat of melting as well as the surface energy from these results. Thus, surface energy of various nanocrystals was found to be widely different for various experimental systems, demonstrating the significance of the environment on thermal properties of nanocrystals. The melting temperature with the inverse sheet thickness, i.e. the GibbsThomson behaviour, is reproduced using atomistic simulations, and is favorably compared to experimental data. The heat of melting as well as surface energy are then extracted from these results.