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.