Structure-dependent chlorine dioxide release from poly(acrylic acid) and hydroxyethyl cellulose hydrogels: Insights from real-time positron annihilation lifetime spectroscopy and quantum chemical calculations.

Chlorine dioxide (ClO₂) is a potent disinfectant used in controlled-release systems for water treatment and antimicrobial purposes. This study investigates ClO₂ release kinetics in poly(acrylic acid) (PAA) and hydroxyethyl cellulose (HEC) hydrogels via positron annihilation lifetime spectroscopy and quantum chemical modeling. PAA hydrogels released ClO₂ 2.5 times faster than HEC, with a 68.7 % decrease in o-Ps lifetime intensity in 12 h, compared to 27.3 % for HEC. This rapid release is linked to PAA's linear, anionic structure, showing binding energies of -24.8 kJ/mol for ClO₂ and - 65.6 kJ/mol for water. HEC hydrogels showed concentration-dependent release; 4 %/w HEC retained 57.6 % more ClO₂ after 24 h than 2 %w/w HEC. Quantum calculations confirmed stronger secondary bond energies for PAA (-24.8 kJ/mol) than HEC (-19.6 kJ/mol) with ClO₂, revealing structure-dependent release mechanisms. These results highlight polymer architecture's critical role in controlled-release behavior, guiding hydrogel-based antimicrobial delivery design for food preservation and water treatment.