Research throws new light on strength of polar bonds

17 November 2021

Theoretical chemist Eva Blokker, affiliated with VU Amsterdam, has recently discovered that the strength of polar bonds is often not determined by the difference in electronegativity between the atoms involved, but by the size of the atoms and the degree to which this leads to mutual repulsion. This discovery runs counter to the electronegativity model described in the scientific literature and textbooks.

Eva Blokker is a PhD student at VU Amsterdam and the Advanced Research Center Chemical Building Blocks Consortium (ARC CBBC), in which, in collaboration with chemical firm Nouryon, she carries out research on the origin of the chemical bond and how this determines the stability and properties of molecules.

Carbon-halogen bonds
Her doctoral research, which is supervised by VU Amsterdam Professor Matthias Bickelhaupt, shows that the electronegativity model does not apply to the carbon-halogen bonds, a series of bonds that are regularly used in textbooks to illustrate the model. This was unravelled by an analysis in which the bond distance between the elements was varied, because only then is it possible to ascertain the driving force behind the formation of the chemical bond. Blokkers’ findings have been published in Chemistry – A European Journal. In fact, her paper appeared on the cover.

Safer and cleaner production processes
Blokker is using this fundamental knowledge to develop new polymerisation initiators. Polymerisation initiators are used in the production of different types of plastics and rubbers. More knowledge about chemical bonds means that new polymerisation initiators can be made that lead to safer and cleaner production processes. Less heat and smaller quantities of volatile substances are released, thus reducing the danger of explosions and air pollution. Blokker explains this in a short video.

ARC CBBC
The Advanced Research Center Chemical Building Blocks Consortium (ARC CBBC) was set up in 2016. In the consortium, AkzoNobel, BASF, Nouryon, and Shell collaborate with the universities of Eindhoven, Groningen, and Utrecht along with scientists from other universities, with the support of the Dutch government, on research in ‘green chemistry’ with as target a sustainable chemical industry. With research focused on (raw) materials and the energy transition; the aim is to create a sustainable society by, among other things, working on energy-efficient production processes and on solutions for converting waste, such as CO₂ and plastics, into sustainable materials.