Substrate effect on the melting temperature of thin polyethylene films

Area of Science:

• Polymer Science
• Materials Science
• Surface Science

Background:

• Semicrystalline polymer thin films exhibit unique properties influenced by substrate interactions.
• Melting temperature (Tm) is a critical parameter affected by film thickness and surface energy.

Purpose of the Study:

• To investigate the strong dependence of crystal orientation, morphology, and Tm on the substrate in semicrystalline polyethylene (PE) thin films.
• To understand the relationship between film thickness, surface interaction, and Tm depression.

Main Methods:

• Fabrication of semicrystalline polyethylene thin films with varying thicknesses.
• Characterization of film morphology, crystal orientation, and melting temperature (Tm).
• Analysis of the influence of substrate-polymer interactions on thermodynamic properties.

Main Results:

• Observed strong dependence of PE thin film crystal orientation, morphology, and Tm on the substrate.
• Tm decreases with decreasing film thickness below a critical threshold.
• Magnitude of Tm depression correlates positively with increasing substrate-polymer surface interaction.

Conclusions:

• Substrate attraction forces compete with interchain forces, driving PE chain crystallization.
• This competition leads to a decrease in overall free energy upon melting, causing significant Tm depression in thin films.
• Surface interactions play a crucial role in governing the thermal properties of semicrystalline polymer thin films.