Effect of hydroxypropyl methylcellulose molecular weight on supramolecular structures and properties of HPMC/sodium citrate photophobic films

Photophobic (white) films were prepared by mixing hydroxypropyl methylcellulose (HPMC) of different molecular weights with sodium citrate (SC). Wide angle X-ray diffractometry, small angle X-ray scattering, scanning electron microscopy, dynamic mechanical analysis, whiteness determination and texture analysis were used to investigate the effect of HPMC molecular weight on the aggregation structures and properties of HPMC film. The crystalline integrity decreased with the increased molecular weight of HPMC for these HPMC/SC films. Similar crystallinity was observed for 6HPMC/SC and 15HPMC/SC, which was larger than that of 50HPMC/SC. All the three HPMC/SC film showed surface fractal structure with similar D-s. With the increasing molecular weight of HPMC, the HPMC/SC film showed honeycomb structures with smaller holes and more compact porous structure, T-g first increased and then decreased a little, the tensile strength and elongation increased with the increasing HPMC molecular weight. 50HPMC/SC films with the smallest pores showed the largest whiteness. A new T-g' peak was observed for HPMC/SC film. (C) 2019 Elsevier B.V. All rights reserved.