Premium
Effect of Shear Flow on the Polymeric Gels Formed by Macroscopic Phase Separation
Author(s) -
Park Moon Jeong,
Char Kookheon
Publication year - 2004
Publication title -
macromolecular rapid communications
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.348
H-Index - 154
eISSN - 1521-3927
pISSN - 1022-1336
DOI - 10.1002/marc.200400042
Subject(s) - materials science , shear rate , shear (geology) , ethylene oxide , shear flow , rheology , composite material , copolymer , neutron scattering , oxide , anisotropy , chemical engineering , scattering , optics , thermodynamics , polymer , physics , metallurgy , engineering
Summary: 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.2D SANS patterns clearly show the memory effect of the hard gels at a pre‐high shear.