Changes in Molecular Weight of Polyacrylate, Ph. Eur., Induced by Temperature, Light, and Time

Abstract

Drug release profiles of formulations coated with polyacrylate, Ph. Eur. (Eudragit® NE30D), may change upon their storage conditions. These drug release changes are investigated by determining the changes in intrinsic viscosity and molecular weight of the polymer induced by temperature, light, and time. Free polyacrylate polymer was obtained by dip casting. The polymer was exposed either for 1 year to temperatures in the range of 5°C to 61°C to check the thermal stability, or for 24 hr to an intensive light source to check light stability. Results show an increase in intrinsic viscosity and an increase in molecular weight of the polymer with increasing temperature and time, indicating an ongoing polymerization of polyacrylate. After light exposure, the intrinsic viscosity as well as the molecular weight of the polymer decreased, indicating a depolymerization of polyacrylate.