Understanding the microstructure of polymer blends used as control release coatings.

Solid oral dosage forms consist of polymer layer encapsulated drug-bound particles with a desired drug release profile e.g. pulsatile, controlled, delayed and targeted, depending upon the polymer(s) employed. Therefore, an intimate understanding of the solution phase polymer-polymer interactions during the deposition of the controlled release film formation is critical to ensure consistent performance (e.g. drug release & stability) of the product. The most common film former is ethylcellulose (EC), whereas the permeability enhancer is often hydroxypropyl methylcellulose (HPMC). Solvency has a pronounced effect on the miscibility of the two polymers within the dispersion, and the resultant film properties. Here, we wish to quantify the solution conformations by SANS of two such polymers in single and binary solutions as a function of solvent composition and temperature.