Preparation and characterization of hydrogels based on homopolymeric fractions of sodium alginate and PNIPAAm

• Published in: Carbohydrate polymers 2013-01, Vol.92 (1), p.157-166
• Main Authors: Leal, David, De Borggraeve, Wim, Encinas, Maria V., Matsuhiro, Betty, Müller, Robert
• Format: Article
• Language: English
• Subjects: absorption; Acrylamides - chemical synthesis; Acrylamides - chemistry; Acrylic Resins - chemical synthesis; Acrylic Resins - chemistry; Alginates - chemical synthesis; Alginates - chemistry; Applied sciences; Biocompatible Materials - chemical synthesis; Biocompatible Materials - chemistry; composite polymers; containers; crosslinking; Drug Carriers - chemical synthesis; Drug Carriers - chemistry; Exact sciences and technology; Glucuronic Acid - chemical synthesis; Glucuronic Acid - chemistry; Hexuronic Acids - chemical synthesis; Hexuronic Acids - chemistry; Homopolymeric fractions; Humans; hydrocolloids; Hydrogels; Hydrogels - chemical synthesis; Hydrogels - chemistry; Materials Testing; Natural polymers; Physicochemistry of polymers; PNIPAAm; Polymers - chemical synthesis; Polymers - chemistry; porosity; scanning electron microscopy; SEM; sodium; Sodium alginate; Starch and polysaccharides; Surface Properties; Temperature; water holding capacity
• ISSN: 0144-8617; 1879-1344
• DOI: 10.1016/j.carbpol.2012.09.031

► Copolymerization of poly-l-guluronic acid with semi-telechelic PNIPAAm was achieved. ► Association of poly-d-mannuronic acid and PNIAAm afforded porous semi-IPN hydrogels. ► Surface morphology of hydrogels was studied by SEM. ► Graft copolymers hydrogels showed better water retention than semi-IPN hydrogels. Graft copolymers were prepared by formation of an amide bond between poly-α-l-guluronic acid (MW 24,000), isolated from sodium alginate and the free amino group of PNIPAAm-NH2. SEM micrographs revealed the formation of a macroscopic network on the surface of the grafted hydrogels with a porosity diameter of 10–20μm. Semi-IPN hydrogels were prepared using different proportions of sodium poly-β-d-mannuronate (MW 21,000), isolated from sodium alginate and cross-linked PNIPAAm-NH2 polymers. SEM micrographs showed porosities of minor size (∼5μm). Though both types of hydrogels are good water containers, the water retention capacity of graft copolymers is more than 50% higher than that of semi-IPN hydrogels. Both hydrogel types showed significant changes in swelling ratios between 20 and 45°C: the swelling ratio decreases near the LCST of PNIPAAm. The water absorption and retention capacity of graft hydrogels increases with pH, reaching a maximum value at pH 7.0.