Water diffusion behavior in epoxy resins with various fluorine contents

Area of Science:

• Polymer Chemistry
• Materials Science
• Spectroscopy

Background:

• Epoxy resins are widely used in various industrial applications.
• Understanding water diffusion in epoxy resins is crucial for predicting material performance and durability.
• Fluorinated polymers offer unique properties, but their interaction with water requires further investigation.

Purpose of the Study:

• To synthesize novel novolac epoxy resins with varying fluorine content.
• To investigate the in situ water diffusion process in these fluorinated epoxy systems.
• To elucidate the role of perfluorinated side chains on water sorption and desorption dynamics.

Main Methods:

• Synthesis of novolac resin with perfluorinated side chains.
• Curing with o-Cresol novolac epoxy resin to create diverse fluorine content materials.
• Attenuated total reflection Fourier transform infrared spectroscopy (ATR/FT-IR) for in situ monitoring.
• Generalized two-dimensional (2D) correlation analysis for sorption/desorption dynamics.

Main Results:

• Water diffusion coefficient initially increased then slightly decreased with higher fluorine content.
• Perfluorinated side chains exhibited opposing effects: enhanced hydrophobicity and increased free volume.
• Two types of water molecules, bound and free, were identified during diffusion.
• Sorption showed bound water changes preceding free water, while desorption reversed this order.

Conclusions:

• Fluorine content significantly impacts water diffusion kinetics in epoxy resins.
• The interplay between hydrophobicity and free volume governs water transport mechanisms.
• Distinct molecular behaviors of bound and free water were observed during sorption and desorption cycles.