Tailoring the Properties of Ethyl Cellulose Membranes Using Hydrophobic Deep Eutectic Solvents

Developing sustainable strategies for the lucrative application of biopolymers is crucial for advancing environmentally friendly materials. Ethyl cellulose, a water-insoluble and biocompatible polysaccharide with excellent mechanical and thermal stability, is a promising material for membrane technology. This study explores nonionic, alcohol-based hydrophobic natural deep eutectic solvents (DES) as green additives for ethyl cellulose membranes. Spectroscopic analyses confirmed the successful incorporation of DES, supported by Hansen solubility parameter predictions indicating dispersive and hydrogen-bonding interactions as key mechanisms. The incorporation of DES markedly enhanced the flexibility of the polymer, lowering the glass transition temperature from 98 °C to below 0 °C. Barrier studies demonstrated that the addition of DES decreased the water vapor permeability and single-gas permeabilities (N₂, CO₂, and O₂) without compromising gas selectivity. Moreover, the Eco-Scale assessment classified the membrane fabrication method as green, confirming improvements in sustainability metrics. Overall, hydrophobic DES are versatile and environmentally benign additives that simultaneously enable the tailoring of mechanical properties and improvement of barrier performance in ethyl cellulose membranes.