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

Area of Science:

• Polymer Science
• Materials Science
• Biomaterials Engineering

Background:

• Physically crosslinked hydrogels are versatile materials with tunable properties.
• Poly (vinyl alcohol) (PVA) hydrogels are widely studied but can benefit from property modification.
• Carrageenan, a natural polysaccharide, can interact with PVA to form composite hydrogels.

Purpose of the Study:

• To investigate the effect of κ-carrageenan addition on the structure, morphology, thermal, and swelling behavior of PVA hydrogels.
• To evaluate the adsorption capacity of these composite hydrogels for crystal violet cationic dye.
• To understand the diffusion mechanism of water within the polymer matrix.

Main Methods:

• Preparation of PVA/κ-carrageenan blend hydrogels via four successive freezing-thawing cycles.
• Characterization of hydrogel morphology, crystallinity, and thermal properties.
• Swelling studies in distilled water and adsorption experiments with crystal violet dye.

Main Results:

• The addition of κ-carrageenan, particularly at a 0.5 weight ratio, significantly increased hydrogel swelling degree and early diffusion coefficients.
• A decrease in polymer matrix crystallinity was observed with carrageenan addition, correlating with enhanced swelling.
• Water diffusion followed anomalous diffusion, indicating a relaxation-controlled transport mechanism.
• The hydrogels exhibited a strong affinity for crystal violet dye due to sulfate groups, achieving a maximum adsorption capacity of 121.4 mg/g.

Conclusions:

• PVA/κ-carrageenan composite hydrogels demonstrate enhanced swelling and water diffusion properties.
• The incorporation of κ-carrageenan improves the adsorption capacity for crystal violet dye, suggesting potential in wastewater treatment.
• The study provides insights into the structure-property relationships and transport mechanisms in these novel hydrogel systems.