Control of particle cluster dispersion using responsive polymeric additives.
The dispersion behavior of clusters of hydrophilic and hydrophobic silica treated with a thermoresponsive polymer has been investigated. The influence of the thermoresponsive interfacial chemistry was assessed by performing dispersion studies in poly(dimethylsiloxane) (PDMS) at 25 and 68 degrees C for agglomerates of powders incorporating poly(N-isopropyl acrylamide) (PNIPAM), a thermoresponsive polymer, and water. While the dispersion of clusters of hydrophilic silica was found to be temperature independent, dispersion of hydrophobic silica exhibited a temperature dependency. The response of the polymer upon temperature variation brings about modifications in the interparticle interactions of the PNIPAM-treated powders thus leading to changes in the cluster cohesivity. The dependence of the cluster cohesivity on temperature was evidenced through changes in the dispersion mechanism and kinetics of the treated silica clusters at both tested temperatures. In addition, optical microscopy of silica suspensions with and without PNIPAM at 25 and 60 degrees C, illustrated the effect of the polymer presence and configuration on the particle-particle interaction forces. While micrographs of the particles at 25 degrees C show less evidence of particle aggregation, the micrographs at 60 degrees C illustrate an increase in aggregation suggesting an enhancement in the attractive forces between particles.
Bava
L
L
Department of Chemical Engineering, Case Western Reserve University, Cleveland, OH 44106, USA.
Feke
D L
DL
Manas-Zloczower
I
I
Rowan
S J
SJ