Comparative study of pluronic-chitosan and pluronic-guar gum composite thermogels

Triblock copolymers display, in water, a rich phase behavior with changes in temperature and concentration that makes them particularly attractive for many industrial and biomedical applications. In an attempt to develop smart carriers with improved properties, additives such as polysaccharides are often included in the poloxamer formulations. In the present work, we examine and compare the associative properties of concentrated aqueous solutions of pluronic F127 in presence of chitosan and guar gum. Dynamic light scattering was used to analyze the effects of the two polysaccharides on the different self-assembled structures formed within these solutions as a function of temperature from the micellization to the sol-gel transition. The most marked differences between the two systems can be observed above the sol-gel transition, where the analysis of the correlation functions evidenced the presence of three processes: a fast process that represents unimers diffusion, an intermediate process related to individual hydrated micelles, and a slow mode due to the presence of large micellar aggregates. We hypothesize that the different molecular weight and ionic character of the polysaccharides are responsible for the different size of the diffusing entities as well for the nature of the bonds which hold together the extended network between micelles formed above the sol-gel transition.