Emmie Lucassen-Reynders

Emmie Helena Lucassen-Reynders (25 February 1935 – 27 January 2023) was a Dutch scientist specialising in colloid chemistry and theoretical physics.

She worked in both academia and in industry.

Lucassen-Reynders was born in Vught.

Her parents were both teachers who met in Zaandam during World War I.

Lucassen-Reynders attended the municipal gymnasium in 's-Hertogenbosch and started her study of chemistry at Utrecht University in 1952.

At the same laboratory she met her future husband Jaap Lucassen in 1958.

After earning her degree, she moved to Unilever in Vlaardingen, where she joined the Physical Chemistry group led by Max van den Tempel.

She graduated in 1959, specialising in Colloid Chemistry and Theoretical Physics at the Van't Hoff laboratory.

Recognising her talents, Van den Tempel encouraged her to work towards a PhD, and in 1962 Lucassen-Reynders defended her dissertation on ‘Stabilization of water in oil emulsions by solid particles’ at Utrecht University in front of Theodoor Overbeek

Lucassen-Reynders' early research considered the impact of fat crystals on the stability of water in emulsions with oils.

Based on the Pickering mechanism, the fat crystals would stabilize this emulsion, in which solid particles are wetted by the continuous phase.

If the emission is water-continuous, the Pickering mechanisms require the solid particles to be polar (for example barium sulfate), whilst in oil-continuous emulsions, the particles must be apolar.

The contact angle is approximately constant and independent of the concentration of particles and type of surfactant.

Lucassen-Reynders used Young's equation and Gibbs' law to explain the relationship between the interfacial tensions and adsorptions of the solid, oil and water.

She continued to investigate the surface equation of state for solutions with surfactants, considering both ionic and non-ionic surfactants.

The consideration of ionic surfactants introduced compilation due to their surface electric potentials, which didn't match the neutral requirements of Gibbs' adsorption law.

In 1964, Lucassen-Reynders spent a year in the United States, where she derived the relationship between surfactant concentration, surface tension and adsorption with ionised surfactants and non-surface-active electrolytes.

She showed that the behaviour of ionised surfactants in oil and water emulsions could be predicted from the behaviour of single components and used the concept of surface electroneutrality to understand how mixing anionic and cationic surfactants impacted adsorption and surface pressure.

In 1969, Lucassen-Reynders moved to England, where she researched surface elasticity and viscosity.

She studied food emulsions, with a focus on interfacial viscoelasticity and emulsification.

Interface Sci 1981;81:150.

surfactants at fluid interfaces.

She moved back to the Netherlands in 1986 and continued her research in the Physical Chemistry group at Unilever Research in Vlaardingen until her retirement in 1997.

Lucassen-Reynders remained active after her retirement, supervising PhD students and continuing to publish.

Much of Lucassen-Reynders’ life work was recognised in an Honorary Note in the leading journal of her field.

Lucassen-Reynders was married to Jaap Lucassen, who she met at the University of Utrecht.

Colloids Surf, A 1994;91:79.

Proteins at Liquid Interfaces.

1996. adsorption of small and large molecules.

Amsterdam: Elsevier Science B.V.; 1998.

p. 341.

behaviour of proteins at water/fluid interfaces in the framework of a two-

Adv Colloid Interface Sci 2002;96:295.

Becher P, editor.

Encyclopedia of Emulsion Technology, vol. 4. New York: Dekker;

Also a physical scientist, Lucassen’s work, including many collaborations with Lucassen-Reynders, is well recognised in an Honorary Note [Advances in Colloid and Interface Science 107 (2004) 1–7 ] and in his obituary.

Together they had two daughters.

Lucassen-Reynders died on 27 January 2023, at the age of 87.

anionic/cationic surfactant systems, I. Equilibrium surface properties.

J Colloid