Thermodynamical characterization of confined indomethacin in MCM-41 pores

We have investigated the adsorption procedures and the thermal properties of confined indomethacin in MCM-41 pores with diameters between 1.64 and 3.8 nm where those pore size is comparable with the molecular size of indomethacin. As a result, the new phase transition that arose from the confining effect is found at higher than conventional glass transition of the bulk indomethacin, a phenomenon unusual in systems with larger pore sizes. The transition temperature is linearly increasing against the inversed pore size, suggesting the presence of a constant energetic term responsible for phase transformation. The proposed explanation involves indomethacin distribution within the pores, with droplets at lower temperatures and a more uniform distribution resembling a dewetting transition at higher temperatures.