Tuning Microbasicity in Poly(vinyl alcohol) Films via Hydrogen-Bonding Network Disruption

The microstructural properties of poly(vinyl alcohol) (PVA) and its composites critically determine their mechanical and optoelectronic performance in flexible sensors, yet their micro acid-base characteristics remain poorly understood despite their importance for pH-responsive functionalities. Here, we report a combined experimental and theoretical study demonstrating that dimethyl sulfoxide (DMSO) incorporation significantly enhances the microbasicity of PVA films. By employing a fluorescent probe and density functional theory calculations, we established that DMSO disrupts water's hydrogen-bonding network, increasing the population of bound water with enhanced basicity. Furthermore, DMSO may also strengthen the hydrogen bonding between the lumichrome probe and bound water, promoting deprotonation. This work provides direct evidence that water with an unsaturated hydrogen-bonding network exhibits elevated basicity, which offers a simple yet effective strategy to tune PVA's acid-base properties. Our findings enable new design principles for advanced proton-transfer-based materials in flexible electronics and smart sensors.