Oxygen Delivery from Ethylcellulose/Calcium Peroxide Composite Films: Effects of Composition and Medium pH

The delivery of O₂ through the reaction of CaO₂ with water is relevant for environmental and biomedical applications, which often operate across a broad pH range. However, the rapid reaction kinetics of CaO₂ can cause an undesirable burst-release effect. Incorporating CaO₂ into hydrophobic polymer matrices is a promising strategy to overcome this limitation. In this study, composite films based on ethylcellulose (EC), a hydrophobic cellulose ether, and varying CaO₂ contents were developed and evaluated for oxygen release under different pH conditions. Surface roughness, hydrophobicity, and film thickness increased with increasing CaO₂ content. Films containing the highest CaO₂ loading (62 wt %) exhibited the greatest surface roughness (12 μm) and a contact angle close to 120°. This formulation most effectively controlled the reaction kinetics, reducing the reaction rate by up to 13-fold compared with pure CaO₂, and produced the highest dissolved O₂ concentrations in buffered media at pH 4.5 and 7.5. In contrast, in deionized water, rapid pH elevation caused by Ca-(OH)₂ formation suppressed O₂ generation. As a proof of concept, the biological effect of oxygen release from the composites was investigated using the root growth of Allium cepa. The results showed that both buffered conditions and excessive CaO₂ content inhibited root development. However, films containing 62 wt % CaO₂ in deionized water enhanced root length, demonstrating that the beneficial effects of oxygen release depend strongly on both the medium characteristics and CaO₂ concentration.