Structures and Adhesion Properties at Polyethylene/Silica and Polyethylene/Nylon Interfaces

Area of Science:

• Materials Science
• Polymer Chemistry
• Surface Science

Background:

• Understanding interfacial molecular structures is crucial for optimizing polymer adhesion.
• Polyethylene's interaction with surfaces like silica and nylon is critical for various applications.
• Maleic anhydride grafting is a common method to enhance polymer compatibility.

Purpose of the Study:

• To investigate the molecular structure changes at buried interfaces of maleic anhydride grafted polyethylene.
• To correlate these molecular changes with adhesion properties on silica and nylon surfaces.
• To elucidate the role of specific functional groups and polymer orientations in adhesion.

Main Methods:

• In situ sum-frequency generation (SFG) vibrational spectroscopy was employed.
• SFG was used to probe the molecular structures of grafted and ungrafted polyethylene films.
• Adhesion properties were measured and correlated with SFG data.

Main Results:

• Grafting maleic anhydride altered polyethylene's interfacial molecular structure.
• The presence of carbonyl (C═O) groups and specific methylene group orientations at silica interfaces correlated with enhanced adhesion.
• Improved adhesion at the nylon interface was observed, but C═O groups were not detected, suggesting disorder.

Conclusions:

• Maleic anhydride grafting significantly modifies interfacial molecular arrangements in polyethylene.
• Specific molecular ordering, including C═O groups and polymer chain orientation, dictates adhesion strength.
• Disordered functional groups may also contribute to adhesion, even if not directly detected by SFG.