Physically Crosslinked Poly (Vinyl Alcohol)/Kappa-Carrageenan Hydrogels: Structure and Applications

This paper discusses the structure morphology and the thermal and swelling behavior of physically crosslinked hydrogels, obtained from applying four successive freezing-thawing cycles to poly (vinyl alcohol) blended with various amounts of kappa-carrageenan. The addition of carrageenan in a weight ratio of 0.5 determines a twofold increase in the swelling degree and the early diffusion coefficients of the hydrogels when immersed in distilled water, due to a decrease in the crystallinity of the polymer matrix. The diffusion of water into the polymer matrix could be considered as a relaxation-controlled transport (anomalous diffusion). The presence of the sulfate groups determines an increased affinity of the hydrogels towards crystal violet cationic dye. A maximum physisorption capacity of up to 121.4 mg/g for this dye was attained at equilibrium.