The Impact of Plasticizer Polarity on the Permeability of Hydroxypropyl Methylcellulose Phthalate Films

The aim of this study was to gain detailed insights into how different plasticizers influence the permeability of isolated hydroxypropyl methyl cellulose phthalate (HPMC-P) films. Since the migration of plasticizers from film coatings may critically affect their functionality, it is essential to monitor the impact of their leaching on the associated film properties. In this work, the leaching behavior of plasticizers from isolated HPMC-P films was estimated using their thermal properties by modulated temperature differential scanning calorimetry (MT-DSC) at varying plasticizer concentrations. The films plasticized with acetyl triethyl citrate (ATEC) and dibutyl sebacate (DBS) exhibited lower permeability compared to those plasticized with polyethylene glycol 400 (PEG 400). This reduced permeability can be attributed to the slower leaching rates of ATEC and DBS and to the persistent hydrophobic character that they impart to the films, even after prolonged aqueous exposure. In contrast, films plasticized with PEG 400 demonstrated the highest permeability because of the hydrophilicity induced in the polymeric films. However, a subsequent decline in their diffusion rate was observed once PEG 400 had leached out of the films. Furthermore, the correlation between leaching behavior and flux profiles provided an understanding of the influence of plasticizer on film permeability based on their polarity. Moreover, saturation in plasticization efficiency was noted with DBS-based films at higher plasticizer concentrations (greater than 10% w/w). Overall, our study highlights the importance of selecting appropriate plasticizers for the development of polymer films and provides insights into tailoring film permeability and drug release kinetics.