Comparison of the Structural and Physical Properties of Two Alginate Ion Complexes with Different Cationic Surfactants

Two types of alginate (Alg) ion complexes were prepared from anionic alginate and two cationic surfactants. The surfactants had the same hexadecyl tail chain and different polar cationic groups: hexadecylpyridinium chloride (HDPyCl) and hexadecyltrimethylammonium bromide (HDTMABr). The Alg ion complexes Alg-HDPy (A-HPy) and Alg-HDTMA (A-HTm) were water-insoluble and soluble in ethanol. The transparent films of the A-HPy and A-HTm were obtained from the alcoholic solutions to study and compare their structures and physical properties using scanning electron microscope (SEM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), small angle X-ray scattering (SAXS), and tensile test. The results showed that the A-HPy and A-HTm powders and films had distinct structures and physical properties, although they possessed the same alginates and alkyl chains with the same carbon number. This study reports that a variety of cationic moieties have different ion-pair formations and controlled inherent bulk structures and properties. Furthermore, the Alg ion complex films showed antibacterial functions, and there were differences with respect to their biological activities.