NMR Spectroscopy and Free Volume Analysis of the Effects of Copolymer Composition on the Swelling Kinetics and Chain Dynamics of Highly Crosslinked Copolymers of Acrylic Acid with PEG-Containing Multiacrylates

摘要

Novel ionizable polymer networks were prepared from oligo(ethylene glycol)(OEG) multiacrylates and acrylic acid (AA), employing bulk radical photopolymerization techniques. The properties of these materials exhibited a complex dependence on te network structure and composition. Penetrant sorption experiments demonstrated that the crosslinked structure of the copolymers depended very strongly on the AA content as well as the number of ethylene glycol groups. The impact of varying the AA content and the oligo(ethylene glycol) chain length on the polymer chain dynamics was examined using diffusion and ~13C NMR relaxation studies. The penetrant uptake studies indicated a coupling of Fickian and relaxation-driven contributions to the swelling behavior. The effect of increasing the AA content on the characteristic chain relaxation time was reversed as teh oligo-ethylene glycol) chain length was varied, indicating that chain relaxation is controlled by structural considerations, for shorter oligo(ethylene glycol) chains, and by compositional considerations, for longer oligo(ethylene glycol) chains. Measured compositional effects on solid state ~13C NMR relaxation times supported these conclusions.