Dynamics of Cyclodimerization and Viscoelasticity of Photo-Crosslinkable PVA

We investigated the interfacial properties of poly(vinyl alcohol) carrying UV-crosslinkable pendant quaternized stilbazole (styrylpyridinium), PVA-SbQ. The extent and dynamics of PVA-SbQ cyclodimerization reactions and crosslinking induced by UV irradiation were monitored in situ and in real time by quartz crystal microgravimetry (QCM). Sensograms reflecting time-dependent changes in density and viscoelasticity of crosslinking films followed a Boltzmann sigmoidal model, depending on precursor film composition and irradiation power. The shifts in QCM frequency and energy dissipation upon PVA-SbQ cyclodimerization correlated with three photo-crosslinking phases involving soft-to-rigid transitions, namely, induction (initiation), main crosslinking (interaction), and termination. PVA-SbQ films crosslinked to different degree were used as protein carriers and a slower release profile was determined for the films that underwent more extensive crosslinking. Overall, this study demonstrates for the first time the dynamics of PVA-SbQ crosslinking and its impact in system viscoelasticity and protein release. (c) 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015, 53, 345-355