Abstract
In the recent studies on chitosan hydrogels, it was found that understanding both rheological and structural properties plays an important role in their application. Therefore, a combination of two independent techniques was applied to investigate micro- and macroscopic properties of chitosan colloidal system. Studies on viscous properties, as well as the sol-gel phase transition process, were performed using rheological methods coupled with the small angle light scattering (SALS) technique. Based on the anisotropy of scattering patterns obtained during rotational shear tests, it was found that the chitosan solution reveals two different behaviors delimited by the critical value of the shear rate. Below a critical value, chitosan clusters are deformed without breaking up aggregates, whereas after exceeding a critical value, chitosan clusters apart from deformation also breakup into smaller aggregates. The values of the radius of gyration determined by applying the Debye function allow one to state that with an increase of chitosan concentration, molecule size decreases. An analysis of the light scattering data from the temperature ramp test showed that with an increase of temperature, the level of polymer coil swelling increases. Simultaneously, the supply of thermal energy leads to a neutralization of the charge of chitosan chains. As a consequence, the formation of intermolecular links occurs and a gel structure is formed.
Highlights
Hydrogels are an interesting group of materials commonly used in medicine and pharmacology [1,2]
The investigation of the viscous properties, as well as the sol-gel phase transition process, carried out using rheological methods coupled with the small angle light scattering (SALS) technique provides a comprehensive survey of the colloidal chitosan solutions behavior
Such studies have shown that in colloidal chitosan solutions, the polymer domains occur in the form of Gaussian coils
Summary
Hydrogels are an interesting group of materials commonly used in medicine and pharmacology [1,2]. In manufacturing of hydrogel matrices for medical applications, biocompatible and biodegradable natural polymers are sought for One such compound is chitosan, a polysaccharide obtained by deacetylation of chitin, which is a natural building component of crustaceans. A suitable buffering and cross-linking agent (e.g., disodium β-glycerophosphate) is used to prepare colloidal chitosan solutions that undergo phase transition under the influence of temperature increase in the physiological pH range [6,7]. In such systems, the main interactions responsible for the sol-gel phase transition are physical intermolecular forces such as hydrophobic interactions among chitosan chains
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