Release kinetics of low molecular weight solutes from mixed cellulose ethers hydrogels: a critical experimental study

Release kinetics in water of five low molecular weight model solutes (urea, cyclohexanone, acetaminophen, phenacetin, cafein) from mixed cellulose eth er hydrogels have been investigated between 20 degreesC and 60 degreesC. Th ree different divinylsulfone crosslinked networks, showing acceptable mecha nical resistance and variable temperature sensitivity tin terms of water sw elling) have been studied. The solute molecular weight (ranging between 60 and 200 x 10(-3) kg mol(-1)) does not seem to play a crucial role for the d iffusion coefficient variation. Network shrinking induced by a temperature increase results in a slight temperature dependency for diffusion coefficie nts. Data interpretation has not been attempted through mechanistic diffusi on models, given the complex structure of mixed cellulose eaters gels. The only approach which leads to an approximate description is based on the fre e volume model developed by Yasuda et al. According to this model, network density is shown to be the main explicating factor of the effective diffusi on coefficient variation. (C) 2001 Elsevier Science Ltd. All rights reserve d.