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Updated: Feb 28, 2026

A Freeze-Thawing Method to Prepare Chitosan-Polyvinyl alcohol Hydrogels Without Crosslinking Agents and Diflunisal Release Studies
Published on: January 14, 2020
A comprehensive spectroscopic study of the polymorphs of diflunisal and their phase transformations
Anuradha R Pallipurath1, Francesco Civati2, Juraj Sibik3
1School of Chemistry, National University of Ireland, Galway, Ireland; Department of Chemistry, University of Bath, Claverton Down, Bath BA2 1AY, UK.
Abstract:
Understanding phase transitions in pharmaceutical materials is of vital importance for drug manufacturing, processing and storage. In this paper we have carried out comprehensive high-resolution spectroscopic studies on the polymorphs of the non-steroidal anti-inflammatory drug diflunisal that has four known polymorphs, forms I-IV (FI-FIV), three of which have known crystal structures. Phase transformations during milling, heating, melt-quenching and exposure to high relative humidity were investigated using Raman and terahertz spectroscopy in combination with differential scanning calorimetry and X-ray powder diffraction. The observed phase transformations indicate the stability order FIII>FI>FII, FIV. Furthermore, crystallization experiments from the gas phase and from solution by fast evaporation of different solvents were carried out. Fast evaporation of an ethanolic solution below 70°C was identified as a reliable and convenient method to obtain the somewhat elusive FII in bulk quantities.
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