The effects of sample mass, interface and surface on the phase transitions and morphology were investigated by DSC and SPM for n-alkyl alcohols and poly(ethylene oxide), PEO. The solid phase transition and the melting temperatures of n-alkyl alcohol shifted to lower temperature with decreasing the mass. Both even and odd carbon number of alcohols classified into 3 groups by the mass dependence of melting and solid phase transition temperatures, which was induced by the crystal morphologies, such as the flat plate, the block on plate and the block. The sample surface influenced the solid phase transition and disturbed to transfer to β or γ phase from α phase with the mass below 30 μg corresponding to 60 layers of bimolecular alcohols. The interface influenced the crystallization mechanism and disturbed the crystallization within 10 layers of bimolecular alcohols. The melting temperature depression was observed with the decrease of sample mass, which was described very well by Thomson-Gibbs equation. The lamellar thickness estimated by T-G equation of PEO with sample mass less than 30 μg was confirmed by SPM observation.
Keywords:Phase transitions, Morphology, Highly sensitive DSC, SPM, n-alkyl alcohol, Poly(ethylene oxide)
Publication Date: 2021-07-25