Preparation of monodisperse, magnetizable, composite metal/polymer microspheres

Abstract

Colloidal microparticles are being increasingly used as microcarriers in bioengineering, immunodiagnostics, and also for “in vivo” uses, for example, in drug targeting or as contrast aids in imaging systems. The advantages of microspheres over traditional supports are mainly related to the high specific surface and the absence of porosity which enhance reaction kinetics. Magnetic particles are even more attractive since they can be collected very simply using a single magnet. Among the different characteristics of the particles, the magnetic properties, internal morphologies, and size distribution are the most important.

In this paper we describe the preparation of monosized magnetic particles made up of a crosslinked polystyrene that entraps finely divided cobalt crystallites. The metal is introduced within performed polymer particles by thermolysis of metal carbonyl complexes. It is shown that nucleophilic pyridine units present in the polymer promote the thermolysis selectively inside the particles. The distribution of cobalt is discussed in relation with the chemical composition and crosslinked level of the microspheres.