Ageing phenomena of chitosan and chitosan–diclofenac sodium system detected by low-frequency dielectric spectroscopy

1999 
Abstract The use of natural polymers for design of dosage form has received considerable attention recently, especially from the safety point of view. Among these polymers, chitosan shows very interesting biological, chemical and physical properties which makes it possible to use chitosan for various pharmaceutical applications. Microcrystalline chitosan (MCCh) is a special multifunctional polymeric material existing in the form of either of gelatinous water dispersion or a powder. Thermal ageing of chitosan and chitosan–diclofenac sodium mixture have been studied using low-frequency dielectric measurements. The ageing was carried out by annealing in ambient atmosphere in the temperature range between 25°C and 100°C. The dielectric losses in the aged samples proved to decrease by about one order of magnitude. The additional measurements of molecular weight distribution and infrared absorption were also carried out for better understanding of nature of the ageing phenomena. Partial evacuation of water, cross-linking and improvement of structural order may be suggested to be a result of thermal ageing of the investigated materials.
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