Surface excess at water/air interface and micellization in solutions of an amphiphilic triblock copolymer

Abstract

PEO-PPO-PEO triblock copolymers (usually referred as EPE) have been employed in different fields, with a remarkable emphasis in biomedical-related applications. They are amphiphilic macromolecules, in which PEO segments are soluble in the aqueous phase, while PPO blocks have hydrophobic character. In this work we carried out experiments with surface tensiometry of aqueous solutions of an EPE copolymer, well-known as Kolliphor P188, as a function of temperature and concentration. From the resultant data, thermodynamic relationships were related to adsorption at non-saturated liquid/air interface (low copolymer concentrations). Surface excess curves were calculated from Kohlrausch-William-Watts (KWW) functions fitted to experimental data and critical micellar concentration, $\mathrm{CMC},$ was determined. The relationship of $\mathrm{CMC}$ and temperature was similar to the observed for the adsorption of EPE copolymer at non-saturated liquid/air interface: there was a drastic change in enthalpy and entropy of adsorption/micellization at $33 °\mathrm{C},$ which was correlated to the critical micellar temperature, $\mathrm{CMT},$ for this copolymer.

Graphical Abstract

Keywords:

• Critical micellar temperature
• PEO-PPO-PEO block copolymers
• water-soluble triblock copolymers
• interfacial tension

Additional information

Funding

The authors thank Brazil’s Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES), and Pró-Reitoria de Pesquisa da Universidade Federal do Rio Grande do Norte (PROPESQ-UFRN) for financial support during the course of this work.