Structure and rheology studies of poly(oxyethylene-oxypropylene-oxyethylene) aqueous solution
- Princeton Univ., NJ (United States)
- Brookhaven National Lab., Upton, NY (United States)
Small-angle neutron scattering (SANS) and rheometry were used to investigate the supramolecular structure formed by a ploy(oxyethylene-oxypropylene-oxyethylene)(PEO{sub 100}PPO{sub 65 }PEO{sub 100}, Pluronic F127) copolymer in aqueous solution over a temperature range of 10-75 {degree}C and a concentration range of 10-20 wt%. At copolymer concentrations of less than 12.5% the solutions are Newtonian fluids. Gels with an ordered structure (cubic packing of spherical micelles) are observed over a well-defined temperature window when the copolymer concentrations are greater than 17 wt%. The SANS results show that the aggregation number of the micelles is independent of temperature and concentrations. Low-yield stresses, very high zero shear viscosities (nearly 10{sup 6} P), and shear thinning are the major rheological characteristics of the gels. Near, but outside, the gel phase boundary the solutions are non-Newtonian (shear thinning). However, SANS shows these solutions contain domains having the same structure as that in the gel phase. The temperature window for ordered structures and non-Newtonian behavior becomes wider with increasing copolymer concentration. The degree of overlap of the micellar shells increases with increasing copolymer concentration at a given temperature and reaches a maximum at nearly 40 {degree}C at a fixed polymer concentration. The yield stress is due to repulsive interactions of PEO chains in the overlapped micellar shell. 36 refs., 16 figs., 2 tabs.
- OSTI ID:
- 420776
- Journal Information:
- Langmuir, Vol. 12, Issue 20; Other Information: PBD: 2 Oct 1996
- Country of Publication:
- United States
- Language:
- English
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