Phase behavior of tri-block copolymers in solution: Mesoscopic simulation study

Abstract

The microphase separation dynamics of tri-block copolymers Pluronic EO17PO60EO17 (P103), EO19PO43EO19 (P84) and EO19PO29EO19 (P65) was simulated in aqueous solution by a dynamic variant of mean-field density functional theory for Gaussian chains. For a Pluronic copolymer with smaller ratio of poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO) (P103, P84 and P65) at low concentration, with an increase of the concentration, the micellar phases change from spherical micelles and micellar clusters, to disk-like micelles for the P103 and P84 solutions, and from spherical micelles to worm-like micelles for the P65 solution. In the P103 and P84 systems, the spherical micelles and micellar clusters can be divided clearly by order parameter, and in the P65 solution the phase separation of worm-like micelle with simulation time is shown clearly by the 3D density field of the PO block. With a decrease of the ratio of hydrophobic PPO and PEO (from P103, P84 to P65), the critical micellar concentration (cmc) increases. It was found that the cmc were 4vol.% for P103, 7vol.% for P84 and 43vol.% for P65. It was concluded that mesoscopic simulation can be considered as an adjunct to experimentation and can provide mesoscopic information otherwise inaccessible (or, not easily accessible) from experimentation.