Purpose. To assess the miscibility and phase behavior of binary blendsof hydroxypropylmethyl cellulose (HPMC) with hydroxypropylcellulose (HPC), methylcellulose (MC), and polyvinylpyrrolidone (PVP).
Methods. Polymer-polymer miscibility was assessed by measurementof the glass transition temperature (Tg) and the width of the glasstransition temperature (W-Tg), using modulated temperaturedifferential scanning calorimetry (MTDSC).
Results. HPMC K4M/PVP and HPMC E5/MC blends were miscibleas evidenced by a single, composition dependent, Tg throughout theentire composition range. HPMC/HPC blends were immiscible at allcompositions. For the miscible blends, the variation in Tg with blendcomposition was compared to the values predicted by the Fox andCouchman-Karasz equations. At intermediate blend compositions,HPMC K4M/PVP blends exhibited negative deviations from idealbehavior. The Tg of the HPMC E5/MC blends was found to followthe Fox equation. The W-Tg measurements of the miscible blends gaveevidence of phase separation at certain compositions.
Conclusions. MTDSC was shown to be a useful technique incharacterizing the interactions between some commonly used pharmaceuticalpolymers.
Financed by the National Centre for Research and Development under grant No. SP/I/1/77065/10 by the strategic scientific research and experimental development program:
SYNAT - “Interdisciplinary System for Interactive Scientific and Scientific-Technical Information”.