Aqueous-based polymeric dispersion: preparation and characterization of cellulose acetate pseudolatex
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The objective of the present study was to prepare and characterize the cellulose acetate (CA) pseudolatex as a semipermeable membrane provider for atenolol gastrointestinal therapeutic system (GITS). For the polymer film coating, it is important to relate the macroscopic properties 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 size of the pseudolatex was reduced to nanometer size range by passing through a microfluidizer. Diacetin was used as the plasticizer. Mechanical 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 160C (unplasticized pseudolatex), 63C (90% plasticizer), 17.6C (110% plasticizer), - 60C (160% plasticizer), and 20.1C (actual film from tablet surface). Approximate F, (free-volume fraction), as a function of diacetin concentration, was estimated by positron annihilation spectroscopy (PAS). There was an increase in F(v) from 5.800 to 6.082 as the diacetin concentration increased from 90 to 170%. Tritium tracer diffusion experiments revealed that the permeability of the pseudolatex films increased as the diacetin concentration increased. The CA pseudolatex provided a mechanically strong film on bilayered osmotically controlled tablet dosage forms.
