Tribology isn’t exactly an area with which us chemists are most familiar, yet chemistry has a great impact on this branch of physics of high industrial importance. Tribology is basically the science which studies the causes and consequences of friction between surfaces.
The plastic bag industry requires the use of chemical additives to reduce the electrostatic adherence between sheets of plastic. My good old friend Dr. Armando Gama has studied through Dissipative Particle Dynamics (DPD) coarse-grained simulations the friction coefficients of having two slightly different molecules: erukamide and behenamide, which only differ in the presence of a double bond between carbon atoms 12 and 13 (Fig1).
In order to study the electronic aspects that give rise to different tribological effects in these very similar molecules, four chains of each kind were bounded to a frozen graphene surface (four bonds apart to prevent steric crowding) and were optimized at the B97D/6-31G(d,p) level of theory.
Double bonds in erukamide pile together through pi-pi stacking interactions (Fig2) which are absent in behenamide which is why these last ones are able to slide better between each other (Fig3). Interaction energies calculated for the inner chains at the same level of theory are 44.21 and 34.46 kcal/mol for erukamide and behenamide, respectively. As per the suggestion of a referee we extended the calculations to a 2D system by placing seven molecules on graphene, which once again was kept at the optimized geometry of its isolated state, at four bonds of separation in order to prevent steric crowding (Fig 4).
This calculations clearly represent a limit case with a high density covering of the surface, but they nevertheless reflect the observed trend that behenamide works better than erukamide in reducing the static friction coefficient between sheets.
The paper is now available at JPC-A. Thanks to Dr. Gama for this great opportunity to work with his team, I know it wont be the last.
Estimado Dr. Barroso, Enhorabuena, un trabajo muy interesante. Gracias por el blog. Un saludo cordial, Fernando
Prof. Dr. Fernando P. Cossío Kimika Organikoa I Saila / Departamento de Química Orgánica I Universidad del País Vasco / Euskal Herriko Unibertsitatea Avda. Tolosa 72 Edificio Korta 4ª Planta 20018 San Sebastián / Donostia Spain Phone: +34 943 01 5442 E-mail: email@example.com
Fernando P. Cossio Ikerbasque, Basque Foundation for Science Scientific Director Maria Diaz de Haro, 3 E-48013 Bilbao, Spain
From: “Dr. Joaquin Barroso’s Blog” Reply-To: “Dr. Joaquin Barroso’s Blog” Date: Wed, 16 Nov 2016 15:13:39 +0000 To: Subject: [New post] Tribology New paper in JPC A
WordPress.com joaquinbarroso posted: “Tribology isn’t exactly an area with which us chemists are most familiar, yet chemistry has a great impact on this branch of physics of high industrial importance. Tribology is basically the science which studies the causes and consequences of friction be”
Dear Prof. Joaquin, I would like thank you for your important contribution by means this scientific place (blog).
I have read this work published at JPCA and I came across with the following statement at pg 9246:
“To confirm this hypothesis” – that the – “reason behind this large energy difference is found to be the interaction between π electrons”…”a perturbation theory calculation at second order was performed to measure the delocalization energies…”
Can you might explain why the MP2, specifically, could help at this hypothesis?
Thanks in advance.