Rheological properties of PE-b-PEG block copolymer in selective solvent

In this study, gelation and rheological behavior of micellar polyethylene-block-polyethyle glycol (PE-b-PEG) copolymers solutions were studied under steady and oscillatory shear fields in various concentrations in water at various temperatures. It was found that in lower concentrations (10 and 15 wt%), Newtonian behavior appears, while on increasing temperature, Bingham plastic trend is shown. At higher concentrations (20 and 25 wt%), viscoplastic behavior was observed. In steady shear experiments, flow curves against temperature exhibited ascending trend for lower concentrations, while a descending trend was discerned for higher concentrations. Such a distinct behavior was ascribed to different interactions of copolymer micelles and solvent. In oscillatory shear field, a minimum in loss modulus against frequency curves was noticed for all concentrations, when temperature exceeded that of sol-gel transition. On increasing temperature, micellar aggregates were formed and solution behavior changed from liquid-like to solid-like type.