Investigation of active substance release from poly(ethylene oxide) hydrogels

The uptake and controlled release of model active substances from poly(ethy lene oxide), (PEO), hydrogels synthesized by irradiation were investigated. For the characterization of network structure of PEO hydrogels, swelling p roperties in water and the number average molecular weight between crosslin ks were determined. Salicylic acid, phthalic acid and resorcinol were used as model substances for their controlled release from PEO hydrogels. The ef fects of dose rate, total dose and chemical structure of active substance o n the uptake and release have been studied. The active substance uptake cap acity of hydrogels was found to be lowest for phthalic acid and highest for resorcinol in the gel system obtained by irradiation both at low and high dose rates. The release was lowest both in rate and in total amounts in hyd rogels containing phthalic acid, more in those with salicylic acid and high est in those with resorcinol. The physical and chemical factors affecting t he release of model compounds such as the network structure of hydrogels an d hydrogen bond formation between the adsorbent and PEO chains were discuss ed. (C) 2001 Elsevier Science B.V. All rights reserved.