Interpenetrating Polymer Network PVA/PAA Hydrogels Prafulla Kumar Sahoo Pradeep Kumar Rana Department of Chemistry, Utkal University, Vani Vihar, Bhubaneswar, India Sarat Kumar Swain Department of Chemistry, North Orissa University, Takatpur, Baripada, India A new type of interpenetrating polymer network (IPN) hydrogel based on polyvinyl alcohol (PVA) networking with difuctional monomer, acrylic acid (AA), and its polymer, polyacrylic acid (PAA), generated in situ, were prepared by a non-conven- tional emulsion method without any added crosslinker, using benzoyl peroxide as initiator and sodium chloride as additive. Structure and bonding in hydrogel due to interpenetrating network were confirmed by infrared spectroscopy. The network- ing was optimized by variation of reaction parameters such as concentrations of additive, monomer, time, and temperature. The response of the hydrogels with and without NaCl was observed by study of their swelling kinetics, and their apparent activation energies for diffusion (E d ) of water were calculated to be 29.28 and 35.97 J mol 1 K 1 with and without NaCl, respectively. The conductivity and pH were measured at different temperatures. The conductivity decreased lar- gely with temperature whereas pH increased in presence of NaCl. The effect of swelling ratio was studied by variation of AA percentage and the optimal PVA=AA AA was determined. Biodegradability of the polymeric network was studied by cul- ture media and the surface morphology investigated by scanning electron microscopy (SEM). Keywords: IPN, hydrogel, swelling kinetics, biodegradability, SEM Received 19 November 2004; in final form 6 December 2004. This work was fully supported by the major research Project from University Grants Commission [MR Project No.F.12-79=2001(SR-II)], Government of India, New Delhi. Address correspondence to Prafulla Kumar Sahoo, Department of Chemistry, Utkal University, Vani Vihar, Bhubaneshwar 751004, India. E-mail: psahoochemuu@satyam. net.in International Journal of Polymeric Materials, 55:65–78, 2006 Copyright # Taylor & Francis Inc. ISSN: 0091-4037 print=1563-5333 online DOI: 10.1080/009140390916440 65