Salah U. Ahmed

Evaluating the efficacy of a group of nontraditional plasticizers on the glass transition temperature of ethyl cellulose polymer.

Objective: The aim of this study was to investigate the efficiency of a homologous series of esters of dicarboxylic acid on ethyl cellulose polymer in terms of their glass transition temperatures (Tg). Methods: Ethyl cellulose polymer was plasticized with succinates (C-2), glutarates (C-5), adipates (C-6), pimelates (C-7), suberates (C-8), and sebacates (C-10) at different concentration levels. The film formation and physical state of plasticizers within the polymer were investigated and incompatibility of plasticizers was determined by nonhomogeneous system. Results: A decrease in Tg of the plasticized polymer was used as an indicator of plasticizing efficiency. Experimental Tg values were correlated with the theoretical ones predicted by Gordon–Taylor equation. Most of the experimental Tg values did not fit with the predicted ones. For all plasticizers (except succinates) the measured Tg was lower than calculated indicating negative deviation from the ideal behavior. Anti-plasticization was obtained with lower plasticizers concentration. Fourier transform infrared spectroscopy was used to determine the interactions between the polymer and plasticizers on Tg values in predicting the efficiency. Conclusions: The correlation between experimental and calculated Tg values verifies that physiochemical properties are the primary factors influencing the plasticization efficiency. However, further studies are needed to establish the plasticization efficiency.

Effect of Neutralization of Poly(Methacrylic Acid-co-ethyl Acrylate) on Drug Release From Enteric-coated Pellets Upon Accelerated Storage

ABSTRACT The effect of neutralization of poly(methacrylic acid-co-ethyl acrylate) or poly(MA-EA) 1:1 (Eudragit® L 30 D-55) on drug release from enteric-coated pellets was studied upon accelerated storage. The dissolution rate of un-neutralized poly(MA-EA)-coated pellets decreased while the neutralized polymer-coated pellets maintained a constant drug release rate. Dynamic mechanical analysis showed that both un-neutralized and neutralized poly(MA-EA) films became rigid on aging. However, the un-neutralized films were affected more than those neutralized. Neutralization of poly(MA-EA) significantly changed the mechanical properties of coating films and improved the stability of poly(MA-EA) enteric-coated pellets upon accelerated storage at the studied conditions.