Mefford O Thompson, Vadala Michael L, Goff Jonathan D, Carroll Matthew R J, Mejia-Ariza Raquel, Caba Beth L, Pierre Timothy G St, Woodward Robert C, Davis Richey M, Riffle J S
Macromolecules and Interfaces Institute, Virginia Tech, Blacksburg, Virginia 24061, USA.
Langmuir. 2008 May 6;24(9):5060-9. doi: 10.1021/la703146y. Epub 2008 Mar 27.
The colloidal stability of dispersions comprised of magnetite nanoparticles coated with polydimethylsiloxane (PDMS) oligomers was investigated theoretically and experimentally. Particle-particle interaction potentials in a theta solvent and in a good solvent for the PDMS were predicted by calculating van der Waals, electrostatic, steric, and magnetic forces as functions of interparticle separation distances. A variety of nanoparticle sizes and size distributions were considered. Calculations of the interparticle potential in dilute suspensions indicated that flocculation was likely for the largest 1% of the population of particles. Finally, the rheology of these complexes over time in the absence of a solvent was measured to probe their stabilities against flocculation as neat fluids. An increase in viscosity was observed upon aging, suggesting that some agglomeration occurs with time. However, the effects of aging could be removed by exposing the sample to high shear, indicating that the magnetic fluids were not irreversibly flocculated.
对由聚二甲基硅氧烷（PDMS）低聚物包覆的磁铁矿纳米颗粒组成的分散体的胶体稳定性进行了理论和实验研究。通过计算范德华力、静电力、空间位阻力和磁力作为颗粒间分离距离的函数，预测了在θ溶剂和对PDMS为良溶剂中的颗粒-颗粒相互作用势。考虑了各种纳米颗粒尺寸和尺寸分布。稀悬浮液中颗粒间势的计算表明，对于最大的1%的颗粒群体，絮凝是可能的。最后，在不存在溶剂的情况下，测量了这些复合物随时间的流变学，以探测它们作为纯流体对絮凝的稳定性。老化时观察到粘度增加，表明随着时间的推移会发生一些团聚。然而，通过将样品暴露于高剪切力可以消除老化的影响，这表明磁性流体没有不可逆地絮凝。
