pH sensitivity and swelling behavior of partially hydrolyzed formaldehyde-crosslinked poly(acrylamide) superabsorbent hydrogels

• Published in: Journal of applied polymer science Vol. 109; no. 2; pp. 1083 - 1092
• Main Authors: Marandi, G. Bagheri, Esfandiari, K, Biranvand, F, Babapour, M, Sadeh, S, Mahdavinia, G.R
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 15.07.2008; Wiley
• Subjects: Applied sciences; crosslinking; Exact sciences and technology; hydrogel; Organic polymers; pH-sensitivity; Physicochemistry of polymers; poly(acrylamide); Properties and characterization; Solution and gel properties; swelling; Absorbent material; Swelling; Crosslinking; pH effect; Absorptivity; Sodium acrylate copolymer; Experimental study; Property processing relationship; Porous material; Formaldehyde; Saponification; Colloidal gel; poly(acrylamide); Chemical modification; pH- sensitivity; Acrylamide copolymer; Acrylamide polymer; Water absorption; Hydrogel
• ISSN: 0021-8995; 1097-4628
• DOI: 10.1002/app.28205

Poly(acrylamide) superabsorbent hydrogel was synthesized through crosslinking method. Formaldehyde was used as a crosslinking agent. To achieve a hydrogel with high swelling capacity, the resulted hydrogels were saponified using NaOH solution at high temperature. During saponification, ammonia gas is produced from hydrolysis reaction of amide groups. The arising of ammonia produces porous structure in hydrogels, which is confirmed using scanning electron microscopy. The conversion of amide groups to carboxylate groups was identified by FTIR spectroscopy. The reaction variables in both crosslinking and hydrolysis reactions that affect the swelling of hydrogels were optimized. The swelling of the hydrogels in various salt solutions with various valencies and radii was studied. Also, the absorbency under load was measured. The hydrogels exhibited pH-sensitivity characteristics. A sharp swelling change was observed in lieu of pH variations in a wide range (1-13). The swelling variations were explained according to the swelling theory based on the hydrogel chemical structure. The pH-reversibility and on-off switching behavior makes the intelligent hydrogels as good candidates for considering as potential drug carries.