Shear induced structures in lamellar phases of amphiphilic block copolymers

The influence of shear on the mesoscopic structure in the lamellar region of ternary poly(ethylene oxide)–b-poly(propylene oxide)–b-poly(ethylene oxide) block copolymers PEO20–b-PPO70–b-PEO20 and PEO100–b-PPO70–b-PEO100 (Pluronic P123 and F127)/water/butanol systems was investigated by different techniques namely: small angle neutron and light scattering (SANS, SALS), as well as birefringence. A transition from parallel to perpendicular alignment of lamellae, with a corresponding decrease in the viscosity, was found with increasing shear rate at high block copolymer concentrations. However, a shear-induced formation of multilamellar vesicles (“onions’') was observed when the polymer concentration was reduced.

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