Structural Investigation of Diol and Triol Poly(oxypropylene)‐Poly(oxyethylene) Block Copolymers Micelles: Composition Dependence, Temperature Response and Clouding Behavior

Abstract

AbstractSolution behavior of two commercially used polyether glycols with poly(oxyethylene) (PEO)‐poly(oxypropylene) (PPO)‐poly(oxyethylene) (PEO) triblock composition—Diol (linear) and Triol (star‐like)—was studied, concerning the concentration and temperature effects until the cloud point (CP). 2‐(2‐butoxyetoxy) ethanol (DB) increased their miscibility with water. The structural study was performed with 25% DB in water, which produced isotropic solutions at room temperature at all polymer concentrations. Micelle's formation was only observed above 40% of polymer, when reversed micelles were formed. The solvent nuclei of the reversed micelles increased with increasing polymer concentrations, caused by dehydration of the PPO chains, then decreased at further higher concentrations, with completely dehydrated hydrophobic chains. When CP is reached, the solvent nuclei are separated by large polymer domains, without phase separation. Neither ordered nor gel phase was formed, probably due to a combination of high miscibility and short hydrophobic segments. The study was performed by Small‐Angle X‐ray scattering (SAXS) and complemented by Fourier‐transformed infrared spectroscopy (FTIR) and dynamic light scattering (DLS). The main contribution of this work is based on the fact that the knowledge of the solubility behavior of Diol and Triol, by changing the solvent or temperature, opens up new possibilities of their use to phase separation processes in industrial applications and delivery systems. Moreover, the elucidation of mechanisms of solubility allows for the design of novel polyether glycols with tailored solution behavior for efficient performance in its target use. All applications rely on their solution behavior and can be benefited from the present results.