The effect of temperature on the surface nature of an adsorbed layer of poly(oxyethylene)-poly(oxypropylene)-poly(oxyethylene) block copolymers

Purpose. To investigate the influence of the temperature at which adsorption takes place and the temperature at which the adsorbed surface is studied on the polarity of Poloxamer adsorbed to a hydrophobic surface. The implication is that changes in surface nature of adsorbed Poloxamer may subsequently be related to functionality, such as changes in opsonisation of Poloxamer coated latex in animals. Methods. The surface energies of Poloxamer surfactant have been calculated following adsorption to silanised glass plates. The adsorption to the plates was undertaken at a range of concentrations and at different controlled temperatures. The contact angles were measured using three different liquids on each surface, at a range of controlled temperatures. The surface energies were calculated using the harmonic mean and the acid-base models, via Wilhelmy plate contact angle measurements. These data were compared with previously published adsorption and hydrophobic interaction chromatography studies. Results. The apolar surface energy term remained consistent, but the polar contribution (which was totally of the electron donor type) changed depending upon the temperature of adsorption (and to a lesser extent the temperature at which the surface energy was measured). The polar nature was most elevated at the critical micelle concentration/temperature. The data are consistent with estimates of surface hydrophobicity made using hydrophobic interaction chromatography. Conclusions, It is argued that the changes in surface energy, which result from the different adsorption conditions, can be expected to influence the functionality of the adsorbed coat, especially for application such as drug targeting.