Ambient Humidity-Dependent Tensile Behavior and Shape Memory Properties of Cinnamoyl Photo-Cross-Linked Poly(2-ethyl-2-oxazoline) Nanofibers

Electrospun, water-stable nanofiber membranes made from hydrophilic, biocompatible poly(2-ethyl-2-oxazoline) (PEtOx) networks hold significant promise in biomedical applications, particularly in wound management. However, their mechanical behavior under varying environmental conditions remains poorly understood. This work provides an in-depth analysis of the tensile properties of photo-cross-linked cinnamoyl-modified high-molar-mass PEtOx (PEtOx-Cin) nanofiber membranes with varying ambient humidity, assessing their practical handling prior to application as wound dressings, while exploring their shape memory properties as basis for potential humidity-actuated wound closure. Cinnamoyl modification and cross-linking of PEtOx-Cin mats significantly improve moisture stability, accelerate moisture sorption, and raise the glass transition temperature (T_g) through newly formed covalent intermolecular bonds. At higher relative humidity (%RH) from 25 to 65%RH, moisture sorption induces plasticization, shifting the T_g below room temperature and transforming the membranes from brittle to highly ductile and elastomeric. This glass-to-rubber transition under ambient conditions enables humidity-stimulated shape memory behavior, revealing excellent temporary shape fixity at low humidity and rapid recovery to the original shape upon exposure to high humidity. The presented findings advance the understanding of cross-linked PEtOx-Cin nanofiber membranes, and while further optimization is needed to enhance mechanical stability at high humidity for improved handling, they underscore their unique potential for next-generation wound closure dressings.