SUPER ABSORBENT HYDROGELS: INTERPENETRATING NETWORKS OF POLY(ACRYLAMIDE-co-ACRYLIC ACID) AND POLY (VINYL ALCOHOL): SWELLING BEHAVIOR AND STRUCTURAL PARAMETERS*

A series of semi- and full interpenetrating networks (IPNs) of poly(acrylamide-co-acrylic acid) and poly(vinyl alcohol) were synthesized by polymerizing an aqueous solution of acrylamide, acrylic acid and N,N/-methylenebis(acrylamide) in the presence of poly(vinyl alcohol) (PVA). PVA was crosslinked with glutar-aldehyde in a subsequent step. The swelling behavior of the IPNs were monitored as a function of composition of the IPNs, extent of crosslinking of PVA, pH and ionic strength of the swelling medium. Incorporation of acrylic acid raises the swelling ratio several fold while crosslinking of PVA suppresses it. The IPNs being ionic, swelling is affected by the pH and ionic strength of the medium. The basic structural parameter of the gel network Mc, the crosslink dimension was calculated using the Flory-Rehner equation. The swelling can be effectively varied by adjusting acrylic acid content and extent of crosslinking of PVA.