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A Comparison of surface and biological properties of chitosan/tannic acid and chitosan/poly(acrylic acid) multilayers

Saraçoğulları, Nihan
Chitosan is a natural polysaccharide which finds use in various biomedical applications due to its important biological properties. Layer-by-layer (LbL) technique is a practical and economical method to functionalize surfaces using interacting polymer pairs. LbL technique can also be used to construct polymer platforms for controlled release of functional molecules from a surface. In this thesis, ultra-thin polymer coatings were prepared using Chitosan and two different weak polyacids, i.e. Tannic Acid (TA) and poly(acrylic acid) (PAA) through LbL technique at moderately acidic conditions. The driving force for multilayer assembly was electrostatic interactions between the protonated amino groups of Chitosan and phenolate groups of TA and protonated amino groups of Chitosan and carboxylate groups of PAA for Chitosan/TA and Chitosan/PAA films, respectively. In addition, hydrogen bonding interactions among the hydroxyl groups of Chitosan and phenolic hydroxyl groups of TA or carboxyl groups of PAA contributed to the association of the polymers at the surface. The surface properties of the films such as LbL growth profile, stability, wettability and surface morphology were examined. The remarkably different surface properties are explained by the chemical nature and acidity of the polyacids. The differences in biological properties of the films such as drug loading capacity, stimuli-responsive release and protein adsorption behaviours are explained by the differences in surface properties. This thesis study generated fundamental information about the structure-property relationship in Chitosan based LbL films and showed tuning both surface and biological properties of the multilayers by simply changing the nature of the polyacid.