Water Vapor Sorption and Diffusivity in Bio-Based Poly(Ethylene Vanillate)-PEV

Area of Science:

• Polymer Science
• Materials Science
• Physical Chemistry

Background:

• Water vapor sorption is crucial for polymer performance and degradation.
• Understanding sorption dynamics in amorphous and crystalline polymers is essential for material design.
• Poly(ethylene vanillate) (PEV) is a polyester with potential applications where water interaction is relevant.

Purpose of the Study:

• To investigate the dynamic and equilibrium water vapor sorption properties of amorphous and crystalline PEV films.
• To compare PEV's sorption behavior with that of polyethylene terephthalate (PET).
• To elucidate the mechanisms governing water diffusion and relaxation in PEV.

Main Methods:

• Gravimetric analysis was used to determine water vapor sorption at 20 °C across 0-95% relative humidity (RH).
• Kinetic sorption/desorption curves were analyzed using the Barens-Hopfenberg model.
• Sorption isotherms and hysteresis were examined to understand water incorporation mechanisms.

Main Results:

• At low RH, sorption followed Fick's law; at higher RH, non-Fickian relaxations occurred, causing isotherm upturn and hysteresis.
• PEV sorption isotherms were comparable to PET, indicating polyester similarity.
• Water diffusion coefficients in amorphous PEV were approximately 10 times higher than in amorphous PET.

Conclusions:

• Non-Fickian relaxations in PEV are linked to increased water uptake and hysteresis.
• Enhanced segmental flexibility of PEV chains contributes to its higher water diffusion rates compared to PET.
• PEV's water sorption characteristics suggest its potential suitability for applications requiring controlled moisture interaction.