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    Effect of plasticizer on the dynamic surface tension and the free volume of Eudragit systems

    Year: 2002

    Journal: International Journal of Pharmaceutics 244 (2002) 81-86, 20111221

    Authors: Romana Zelko , A. Orban , K. Süvegh , Z. Riedl , I. Racz

    Organizations: a Institute of Pharmacy Administration, University Pharmacy, Semmelweis University, Högyes E. Street 7-9, H-1092 Budapest, Hungary b Gedeon Richter Ltd., Gyömröi Street 19- 21, H- 1103 Budapest, Hungary c Department of Nuclear Chemistry, Eötvös Lorand University, P.O. Box 32, H- 1518 Budapest 112, Hungary d Pharmaceutical Institute, Semmelweis University, Högyes E. Str. 7, H- 1092 Budapest, Hungary

    The purpose of the present study was to determine the changes of dynamic surface tension of aqueous Eudragit dispersions quantitatively and compare these data with the free volume of the free films formed from several dispersions of different dibutyl sebacate (DBS) concentrations. Eudragit L 30D and Eudragit RL 30D aqueous colloidal polymer dispersions and their cast free films were examined. The concentration of DBS varied in the dispersions from 0 to 20%. The dynamic surface tension of the dispersions were measured by the Du Nouy ring method while the free volume of cast films were determined by positron annihilation spectroscopy. The obtained results show that dynamic surface tension measurements indicate the white point (WP) of Eudragit dispersions by a significant standard deviation increase. This may suggest the applicability of dynamic surface tension measurements for the determination of the WP of polymeric dispersions. A decrease in the WP temperature of Eudragit dispersions with an increasing plasticizer concentration was observed up to the DBS concentration of 10% w/w. Above this concentration neither the WP of the polymer dispersion nor the free volume of the free films of the polymer were changed remarkably.