Engineering Pore Accessibility in PVA/Cellulose Nanocrystal/Ca2+ Composite Aerogels for Enhanced Drug Adsorption and Sustained Release

While poly (vinyl alcohol) (PVA)-based aerogels are promising porous carriers for controlled drug delivery, drying-induced pore collapse generally limits their internal pore accessibility, drug-loading capacity, and release regulation. In this study, duration-controlled tert-butanol (TBA) solvent exchange was developed as a pore-engineering strategy to regulate the structure-performance relationship of PVA/cellulose nanocrystal/Ca2+ composite aerogels. This strategy focuses on balancing pore preservation, liquid-accessible pore connectivity, and network densification, instead of simply increasing the total surface area. With an optimized exchange duration, the TBA6 aerogel exhibited a well-preserved porous network. Moreover, its specific surface area and porosity increased from 33.11 to 96.02 m2·g−1 and from 93.93% to 96.03%, respectively. This optimized structure enhanced salicylic acid (SA) loading, elevating the equilibrium adsorption capacity from 40.91 to 61.18 mg·g−1. Release kinetic analysis revealed that the Higuchi constant and the Korsmeyer-Peppas release constant decreased from 18.148 to 12.751 and from 25.070 to 17.283%·h−1/2, respectively, indicating a slower diffusion-regulated release process. Confocal Raman mapping further confirmed that TBA6 promoted a more homogeneous SA distribution within the aerogel matrix and enabled gradual release from the internal porous network. To sum up, controlling solvent-exchange duration is an effective strategy for tuning pore accessibility and diffusion resistance. This study provides new insight into the design of PVA-based composite aerogels for drug-loading and sustained-release applications.