Fabricating ternary hydrogels of P(AM-co-DMAEMA)/PVA/β-CD based on multiple physical crosslinkage

Ternary hydrogels composed of poly[acrylamide- co -2-(dimethylamino)ethyl methacrylate] [P(AM- co -DMAEMA)], poly(vinyl alcohol) (PVA) and β -cyclodextrin ( β -CD) were fabricated based on the multiple physical interactions such as inclusion complexation, hydrogen bonding and polymer crystallinity , and exhibited high storage modulus . To illustrate the individual role of each physical interaction, symmetrical investigation has been performed. P(AM- co -DMAEMA)s with two compositions , prepared by radical polymerization at −20 °C below the freezing point of reaction medium of water, were served as the inclusion guest for the inclusion host of β -CD. The inclusion complex between dimethylaminoethyl group of DMAEMA and β -CD was identified through 2D NOESY NMR spectroscopy . Hydrogen bonding between each pairs of hydrogel components was confirmed with FTIR analysis and contributed the second form of crosslinkage. Under freezing polymerization and further freezing-thawing treatment, PVA component tended to crystallize to serve as the third type of physical crosslinkage, which was recognized with X-ray diffraction. Rheological and thermo-gravimetrical analysis was used to inspect the modulus and thermal stability of the hydrogels, respectively. Three hydrogels of P(AM- co -DMAEMA)/PVA-g- β -CD, P(AM- co -DMAEMA)/PVA/ β -CD and P(AM- co -DMAEMA)/PVA were synthesized under the same condition to make the comparison. The whole results disclosed the strong dependence of hydrogel properties on the hydrogel components, reflecting the synergistic effects of different physical crosslinkages for the formation of those physical hydrogels.