CONICET | Buscador de Institutos y Recursos Humanos

The adsorption of macromolecules at interfaces is of great interest for various industrial applications. The possibility of controlling the properties of colloidal dispersions by the use of adsorbing polymers requires detailed knowledge of the polymer structure and adsorption characteristics. The interfacial behaviour at the A/W and at O/W interface of different commercial types of HPMC, so called E4M, E50LV, E15LV and E5LV was firstly measured by means of tensiometry. The surface pressure isotherm at the A/W interface was sigmoidal. At lower HPMC bulk concentrations (1×10-6 wt %), E4M showed surface activity while higher concentrations were necessary for E50LV, E15LV and E5LV. p-C isotherms presented inflexions as the HPMC bulk concentration increased (except for E50LV), related with different structural patterns adopted by the polysaccharide segments at the A/W interface. The behavior of HPMC at the O/W interface resulted different. The adsorption isotherm had softer slopes when increasing the bulk polysaccharide concentration, denoting the absence of any change in the structure of the adsorbed monolayer. Such a different behavior of HPMCs at the O/W interface could obey to the different nature of this system, where fatty acids are constituting the hydrophobic phase. The order in the interfacial activity at the O/W interface was: E4M >E50LV> E15LV = E5LV. The adsorption dynamics for the highest molecular weight HPMC, seems to be at the first sight clearly similar at both interfaces, i.e. the curves shape, although the surface pressure values were lowest at the O/W interface. This trend keeps correspondence with that obtained from the p-C isotherms were the equilibrium p values were lower at the O/W interface.

enviar mensaje