Sorption induced relaxations during water diffusion in S-PEEK.

Area of Science:

• Polymer Science
• Materials Science
• Physical Chemistry

Background:

• Sulfonated poly(ether ether ketone) (S-PEEK) is a promising polymer for various applications.
• Understanding water sorption kinetics is crucial for predicting material performance and durability.
• Glassy polymers often exhibit complex diffusion behaviors.

Purpose of the Study:

• To analyze the sorption kinetics of water vapor and liquid water in S-PEEK.
• To quantify the contributions of Fickian diffusion and relaxational phenomena to water uptake.
• To investigate the influence of water concentration on these mechanisms.

Main Methods:

• Experimental determination of sorption isotherms using a gravimetric sorption balance.
• Application of the Hopfenberg and Berens model to quantify Fickian diffusion and relaxation.
• Analysis of sorption kinetics under both water vapor and liquid water conditions.

Main Results:

• Both Fickian diffusion and relaxational phenomena are observed even at low water concentrations in S-PEEK.
• The relative importance of relaxation increases, while Fickian diffusion decreases with rising water concentration.
• Fickian diffusion coefficient shows a two-order-of-magnitude increase with water vapor concentration and a three-order-of-magnitude increase considering liquid water sorption.

Conclusions:

• Water sorption in S-PEEK is a complex process involving both diffusion and relaxation.
• The interplay between Fickian diffusion and relaxation is concentration-dependent.
• Accurate modeling requires consideration of both phenomena for predicting S-PEEK behavior in humid environments.