Original Articles: 2015 Vol: 7 Issue: 1
Thermodynamic and interfacial studies on solid dispersions of phenothiazine- 2-methylimidazole drug system
The study of solid liquid dispersions of binary drug system has been very useful in providing the significant enhanced pharmaceutical properties as compared to the parent drug. The present communication includes the thermodynamic and interfacial investigation of phenothiazine (PT) and 2-methylimidazole (MIM) binary eutectic and non-eutectic drug dispersion. Simple eutectic dispersion was observed at 0.785 mole fraction of MIM at melting temperature 122°C. Partial and Integral thermodynamic quantities such as, excess Gibbs energy (gE), excess enthalpy (hE), excess entropy (sE) of eutectic and non-eutectic mixtures were also calculated using activity coefficient data. The value of excess Gibbs free energy indicates positive deviation from ideal behaviour which refers stronger association between like molecules during formation of binary mix. However, the negative value of mixing function as Gibbs free energy of mixing (DGM) suggests the mixing for eutectic and non-eutectic is spontaneous. The interfacial properties such as entropy of fusion per unit volume (DSV), interfacial energy (s), roughness parameter (α), grain boundary energy of parent components, eutectics and non-eutectics have been studied using enthalpy of fusion data. Gibbs-Thomson coefficient evaluated by numerical method is also very helpful to compute the interfacial energy. The size of critical nucleus at different undercoolings has been found in nanoscale, which may lead a big challenge in pharmaceutical world. The value of α > 2, suggests the irregular and faceted growth proceeds in binary alloys.