THE EFFECT OF TEMPERATURE ON THE SURFACE NATURE OF AN ADSORBED LAYER OF (OXYETHYLENE)-POLY(OXYPROPYLENE)-POLY(OXYETHYLENE) BLOCK-COPOLYMERS

Purpose. To investigate the influence of the temperature at which adso rption takes place and the temperature at which the adsorbed surface i s studied on the polarity of Poloxamer adsorbed to a hydrophobic surfa ce. The implication is that changes in surface nature of adsorbed Polo xamer may subsequently be related to functionality, such as changes in opsonisation of Poloxamer coated latex in animals. Methods. The surfa ce energies of Poloxamer surfactant have been calculated following ads orption to silanised glass plates. The adsorption to the plates was un dertaken at a range of concentrations and at different controlled temp eratures. The contact angles were measured using three different liqui ds on each surface, at a range of controlled temperatures. The surface energies were calculated using the harmonic mean and the acid-base mo dels, via Wilhelmy plate contact angle measurements. These data were c ompared with previously published adsorption and hydrophobic interacti on chromatography studies. Results. The apolar surface energy term rem ained consistent, but the polar contribution (which was totally of the electron donor type) changed depending upon the temperature of adsorp tion (and to a lesser extent the temperature at which the surface ener gy was measured). The polar nature was most elevated at the critical m icelle concentration/temperature. The data are consistent with estimat es of surface hydrophobicity made using hydrophobic interaction chroma tography. Conclusions, It is argued that the changes in surface energy , which result from the different adsorption conditions, can be expect ed to influence the functionality of the adsorbed coat, especially for application such as drug targeting.