On the Fragility of Hydroxypropyl Methylcellulose as Measured via Broadband Dielectric Spectroscopy

A special class of hydroxypropyl methylcellulose polymer (HPMC) has been developed for the production of amorphous solid dispersions of active pharmaceutical ingredients by hot-melt extrusion. The new HPMC materials are novel in that they have low glass transition temperatures (T_g ≈ 100 °C) that enable them to be melt processed without plasticizers. This has produced the opportunity to acquire frequency-dependent T_g measurements of HPMC via broadband dielectric spectroscopy (BDS). Our study revealed that the fragility (m) of this polymer is very low (m = 16.9 ± 0.4). Although the measurements herein are limited to this type of HPMC, it is hypothesized that this low fragility is not unique to this particular grade of HPMC.