Electrospun Shape-Stabilized Phase Change Materials Based on Photo-Crosslinked Polyethylene Oxide.

Phase change materials (PCMs) in the form of fibers or fibrous mats with exceptional thermal energy storage ability and tunable working temperature are of high interest to produce smart thermoregulating textiles, useful for increasing human thermal comfort while avoiding energy waste. Common organic PCMs suffer from instability in their molten state, which limits their applicability as highly performing fibrous systems. In this work, electrospun fibrous mats made of polyethylene oxide (PEO), a PCM with excellent thermal properties and biocompatibility, were fabricated and their shape instability in the molten state was improved through UV photo-crosslinking. The characterization aimed to assess the performance of these shape-stable electrospun mats as nanofibrous PCMs for thermal management applications. In addition to an enhanced resistance to water-based solvents, UV-cured electrospun PEO mats demonstrated a remarkable latent heat (≈112 J/g), maintained over 80 heating/cooling cycles across the phase change temperature. Moreover, their morphological stability above their melting point was demonstrated both macroscopically and microscopically, with the retention of the initial nanofibrous morphology. Tensile mechanical tests demonstrated that the UV crosslinking considerably enhanced the ultimate properties of the fibrous mat, with a five-fold increase in both the tensile strength (from 0.15 MPa to 0.74 MPa) and the strain at break (from 2.5% to 12.2%) compared to the uncrosslinked mat. In conclusion, the photo-crosslinked electrospun PEO material exhibited high thermal properties and good shape stability without displaying leakage; accordingly, in the proposed PCM system, the necessity for encapsulation or use of a supporting layer has been eliminated. Photo-crosslinking thus proved itself as an effective, fast, and environmentally friendly method to dramatically improve the shape-stability of nanofibrous PEO electrospun mats for smart thermoregulating textiles.

Photo-crosslinking of chitosan/poly(ethylene oxide) electrospun nanofibers.

Photo-crosslinked nanofiber mats containing chitosan were obtained through the versatile and promising technology of electrospinning. Due to the challenging processability of chitosan by electrospinning because of its stiffness and polycationic nature, it was blended with easily-spinnable poly(ethylene oxide). The optimum conditions for electrospinning of chitosan/poly(eyhylene oxide) (CS/PEO) blends were selected for further characterization and investigation: the composition of CS/PEO 70/30 mass fraction was chosen as it allowed to produce uniform and defect free electrospun mats formed by fibers with an average diameter of 270 nm. In order to improve the physico-chemical properties (in particular the stability and water resistance) of the electrospun mats, electrospinning was coupled with the fast and eco-friendly technique of photo-crosslinking. The photo-curing reaction of the CS/PEO fibers, as well as the morphology, thermal properties and water resistance of the electrospun mats before and after application of UV irradiation, were investigated. The photo-crosslinking process was optimized in order to fabricate CS/PEO electrospun mats which are resistant to water and thus can enlarge the application of such membranes, especially in biomedical, filtration and food industries.

Investigating the effect of different transducer stiffness values on the contactin complex detachment by steered molecular dynamics.

This study investigated the adhesion behavior of Contactin4 (CNTN4), a member of Immunoglobulin Super Family (Ig-SF) of cell adhesion molecules. Contactin4 plays a crucial role in the formation, maintenance, and plasticity of neuronal networks. Contactin in its complex configuration with protein tyrosine phosphatase gamma (PTPRG) was selected for simulation. By utilizing Steered Molecular Dynamics (SMD), the uniaxial force was applied to induce unbinding of the complex, and the force-induced detachment of complex components was probed. Three sets of simulations with three values of transducer stiffness and five pulling speeds were designed. Our results showed the dependence of unbinding force on both accessible parameters of pulling speed and spring stiffness. By increasing the stiffness value and pulling speed the rupture force increased. Accordingly, the dissociation rates due to the Bell's theory based on rupture forces and loading rates were calculated.