Theodoor Overbeek

Jan Theodoor Gerard Overbeek (Groningen, January 30, 1911 – February 19, 2007) was a Dutch professor of physical chemistry at the Utrecht University.

Overbeek was born in Groningen. Overbeek's family moved to Rotterdam in 1913 and to Breda in 1925. Overbeek went to study chemistry (from 1928-1933) at the Utrecht University. He spent a year in military service and then worked for two years in Belgium. First year he worked with Jacques Errera at the Université libre de Bruxelles, after that a year with Arend Joan Rutgers at Ghent University.

He revieved his doctorate on May 19, 1941 with a thesis Theory of Electrophoresis, the Relaxation Effect (Theorie der electrophorese: het relaxatie-effect). All the characteristic features of the later work of Overbeek were present already in his thesis: formation of a simple model with the available data, set up the corresponding equations and then rigorous mathematical elaboration. Overbeek's dissertation explored the role of the deformation of the electrical double layer surrounding a charged colloidal particle which was set in motion by an external electric field.

After graduation Overbeek joined Philips, where Evert Verwey, was his immediate boss. In addition to work on luminescent screens they worked together on the interaction between colloidal particles. Attraction, based on the summation of the London - van der Waals interactions between the atoms was established in 1937 by Hamaker who also worked at Philips. However, the details on the repulsion produced by the electric double layer around colloidal particles were not so clear. By using thermodynamic considerations, the relevant free energies were calculated and interaction potential were derived. This research resulted in a seminal work Theory of the Stability of Lyophobic Colloids. The work had a great influence, and is still used by considerations about the stability of colloids, but also in various other fields where charged surfaces interact with each other. The whole of that theory is now known as DLVO (Derjaguin, Landau, Verwey, Overbeek) theory.

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