In situ observation of the melting behaviour of PEO single crystals on a PVPh substrate by AFM

The melting of PEO single crystals placed on an Si wafer and PVPh thin films with different thicknesses was studied. The results show that PEO/substrate interactions have a pronounced influence on the melting temperature of the PEO single crystals and spreading behaviour of the PEO melts. The melting point of the PEO single crystals placed on the PVPh sublayer depends on the thickness of the PVPh layer. A melting point depression of the PEO single crystal was observed with increasing PVPh layer thickness. This has been correlated to the enhanced interaction between PEO and PVPh based on hydrogen bonding. It is speculated that the thickening of the PVPh layer is in favor of the formation of hydrogen bonds between PVPh and PEO due to the increased amount of exposed hydroxyl groups of PVPh and their ability to build hydrogen bonds with the oxygen groups of PEO.