AQUEOUS-BASED POLYMERIC DISPERSION - PREPARATION AND CHARACTERIZATIONOF CELLULOSE-ACETATE PSEUDOLATEX

The objective of the present study was to prepare and characterize the cellulose acetate (CA) pseudolatex as a semipermeable membrane provid er for atenolol gastrointestinal therapeutic system (GITS). For the po lymer film coating, it is important to relate the macroscopic properti es such as tensile strength and toughness to the atomic-scale property , free-volume. Using ethyl acetate as the solvent, CA pseudolatex was prepared by a phase inversion emulsification technique. The particle s ize of the pseudolatex was reduced to nanometer size range by passing through a microfluidizer. Diacetin was used as the plasticizer. Mechan ical properties showed a considerable decrease in their values except % elongation as the plasticizer concentration increased from 90 to 150 %. Glass transition temperatures of the CA pseudolatex membranes were 160 degrees C (unplasticized pseudolatex), 63 degrees C (90% plasticiz er), 17.6 degrees C (110% plasticizer), -60 degrees C (160% plasticize r), and 20.1 degrees C (actual film from tablet surface). Approximate F-v (free-volume fraction), as a function of diacetin concentration, w as estimated by positron annihilation spectroscopy (PAS). There was an increase in F-v from 5.800 to 6.082 as the diacetin concentration inc reased from 90 to 170%. Tritium tracer diffusion experiments revealed that the permeability of the pseudolatex films increased as the diacet in concentration increased. The CA pseudolatex provided a mechanically strong film on bilayered osmotically controlled tablet dosage forms. (C) 1998 Elsevier Science B.V. All rights reserved.