1999 Volume 27 Issue 3 Pages 161-164
Effects of base hydrophobicity on a flow behavior and a microstructure of aqueous suspension of core-shell type carboxylated polymer particle have been studis. The suspension was neutralized by NaOH, dimetylaminoethanol(DMAE), dimetylaminopropanol(DMAP) and dimetylaminobutanol(DMAB). Steady shear flow was measured with a coni-clinder rotational rheometer, and microstructure was examined with a dynamic oscillating shear method and the small angle X-ray scattering(SAXS) method. The hydrophobicity is DMAB>DMAP>DMAE>NaOH. The distance ξ between center to center of neighboring particles in ordered structure made of the particles was measured by SAXS method. In case of NaOH, the suspension indicated shear-thinning flow. Loss tangent tan δ was below 1(G'>G") in all frequency region and a diffraction peak in SAXS profile was detected. These results show the three dimensional network structure of ordered structure is formed in the suspension. As the hydrophobicity increased, viscosity and degree of shear-thinning decreased, tan δ became above 1 in almost frequency region and the height of diffraction peak decreased without changing ξ. These results suggest that, as the base hydrophobicity increased, the three dimensional network structure reduces to the isolated domain structure, though the distance between neighboring particles in ordered structure does not change.
