An expedient in to the phase behaviour and scattering profile in PEO-PPO-PEO block copolymer mixed systems in aqueous solution

Abstract

The present study aims to develop copolymeric micelles giving an account on the clouding behavior of two series of poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (PEO-PPO-PEO) block copolymers with varying molecular weight of PPO: one with moderate hydrophilicity i.e., 40 % PEO (L64, P84, P104) blended with very hydrophobic copolymers i.e., 10 % PEO (L61, L81, L101, L121). Marked changes in the solution behavior in our mixed copolymeric solution systems depicted the micellization and micelle growth/ transition along with the phase separation (2ϕ) which is well explained from cloud Point (CP) and solution relative viscosity (ηrel) study. The CP analysis showed the lower cloud point (LCP) and the conventional upper cloud point (UCP) i.e., two marvelous CP in the aqueous mixed Pluronics® system which motivated to explore the hypothesis of double cloud point. Such shifting phenomenon from LCP towards UCP demonstrated an increment in dynamic light scattering (DLS) intensity resulting in the obvious increment in the micellar dimensions i.e., hydrodynamic diameter (Dh) for the examined mixed copolymeric system. In addition, the small-angle neutron scattering (SANS) data were fitted to obtain the predictable parameters such as, hard sphere radius (Rhs), aggregation number (Nagg) and micellar morphology. Our findings corroborated the micellar transition from spherical to elongated ellipsoidal micelles with temperature ageing depicting a strong dependence on the amphiphilicity and concentration of the two BCPs in the mixed solution environment.