Macromolecular Rapid Communications, Vol.25, No.11, 1082-1089, 2004
Effect of shear flow on the polymeric gels formed by macroscopic phase separation
Shear-induced phase behavior of poly(ethylene oxide-b-(DL-lactic acid-co-glycolic acid)-b-ethylene oxide) (PEO-PLGA-PEO) triblock copolymers in water is investigated using rheology and small-angle neutron scattering equipped with an in situ Couette shear cell. For gels formed by the macroscopic phase separation, the steady shear experiment reveals that the flow-induced anisotropy on a nanometer length scale at a critical shear rate and the phase separation on a larger length scale are successively induced with a further increase in the shear rate. In particular, the hard gels show a memory effect inscribed by a pre-high shear in contrast to the soft gels.