Poly(N-isopropylacrylamide)/poly(vinyl alcohol) semi-interpenetrated hydrogels: structural, mechanical, and bioadhesive properties

Poly(N-isopropylacrylamide) (PNIPAAm) hydrogels are promising for biomedical applications; however, balancing mechanical stiffness and bioadhesion remains challenging. In this study, PNIPAAm/poly(vinyl alcohol) (PVA) semi-interpenetrating polymer networks (semi-IPNs) were synthesized through a single-step process and systematically characterized. FTIR analysis provided evidence consistent with physical interactions, including possible hydrogen bonding, between PVA and PNIPAAm. Increasing PVA content enhanced swelling capacity and water diffusion while maintaining thermosensitivity. Morphological analysis revealed reduced pore size and enhanced structural homogeneity, with pore-size distributions accurately described by a Weibull distribution. Under cyclic compression, semi-IPNs showed high elasticity, recovery, and structural integrity, though stiffness decreased with increasing PVA content, consistent with steric hindrance. Bioadhesion exhibited a non-monotonic dependence on PVA content, reaching a maximum at a PVA:NIPAAm mass ratio of 0.63:1. Overall, PVA incorporation effectively tailors swelling, diffusion, bioadhesion, and mechanical resilience, highlighting the potential of these semi-IPNs for tissue-contacting and bioadhesive interfaces.