Figure 1.

Water-induced adhesion of pectin films cured in parallel. (A) Schematic of pectin films in glass phase (gray) and gel phase (blue). The (–) indictes no adhesion, whereas (+) indicates an adhesive interaction between films. (B) Using a previously defined adhesion assay [35], pectin films were gently compressed (5N) for a 60 s development time followed by withdrawal of the films at 0.5 mm/s. Two glass phase films (Ai) demonstrated no adhesion. Hydration of one (Aii) or both (Aiii) of the films to 15% water content resulted in significant adhesion. An equal volume of water placed on the glass phase films as droplets (Aiv) resulted in comparable adhesion to two gel films. (C) In the droplet assay, adhesion was largely independent of probe speed (that is, the speed at which the films were compressed). (D) Scanning electron microscopy (SEM) of two films following droplet compression shows evidence of polymer chain entanglement at the film interface (arrows at film interface).