Determination of Hamaker constants of polymeric nanoparticles by asymmetrical flow field-flow fractionation

The existing interaction forces between all objects are either of repulsive or attractive nature. Concerning attractive interactions, the determination of dispersion forces are of special interest since they appear in all colloidal systems and have a crucial influence on the properties and processes in these systems. The dispersion forces relate to the polarizability of the substances and can be described by several theoretical models.[1] One possibility to link theory and experiment is the description of the London-Van der Waals forces in terms of the Hamaker constant, which leads to the challenging problem of calculating the van der Waals interaction energies between colloidal particles[1]. Hence, an exactly determined Hamaker constant for a given material is needed when interfacial phenomena such as adhesion are discussed in terms of the total potential energy between particles and substrates. The determination of the effective Hamaker constants of systems like object-mediumobject yields information about dispersion interactions in the system and thus is of substantial interest.[1] Recently, Karaiskakis et al. reported on the determination of Hamaker constants by sedimentation FFF.[2] In this work, the asymmetrical flow field-flow fractionation (AF-FFF) in combination with a Newton algorithm based iteration process was used for the determination of Hamaker constants of different nanoparticles with different architectures in toluene.[3,4] The particles are characterized by dynamic light scattering and transmission electron microscopy and fractionated by AF-FFF.[5-7] The obtained experimental data were used to evaluate the effective interaction parameters. The calculated Hamaker constants agree well with literature data.