Molecular motion in tire rubber


Scientists have observed the molecular motion of rubber components typically used in automobile tires—polybutadiene and carbon black—with the world’s fastest time resolution. The study reveals a clear interaction between the two components on the atomic scale, paving the way towards improved diagnostics of tire rubber degradation and the development of materials with enhanced durability.

Structure of two different rubber samples. Top: Schematic illustration of sample L3026C of tire rubber containing graphitized carbon black (CB), with little interaction between CB and polybutadiene (PB). Bottom: Schematic illustration of sample L3026F of tire rubber containing non-graphitized CB. The CB surface and PB are strongly bonded and largely interact, resulting in better properties of the material for automobile tire performance.

Tire rubber is a composite material that typically includes synthetic rubber, such as polybutadiene, and added nanoparticles, such as carbon black, to improve its physical properties. During driving, strong forces act on the tire, causing its components to move against each another, which can lead to wear and degradation of the material. To evaluate tire performance, it is therefore important to understand not only the static structure of the complex particle network formed by the polymer and the nanoparticles, but also their interaction and respective movements, as these dynamics directly influence material properties such as wear resistance. Because some of these molecular movements happen extremely quickly, time-resolved measurements at atomic resolution on the fastest possible time scale are critical for developing and validating dynamic models of such materials.  

An international research team led by scientists from the University of Tokyo, Ibaraki University, and European XFEL has now observed the molecular motion within samples of polybutadiene and carbon black, which occurs naturally as a result of the material structure, with a time resolution of 890 nanoseconds (billionths of a second)—the fastest resolution obtained in such studies so far—at the European XFEL’s SPB/SFX instrument. 

Read more on the European XFEL website

Someday you will get to play with those electrons!

Razib Obaid is a project scientist at the Linac Coherent Light Source (LCLS) at SLAC in California. LCLS is one of 7 free electron lasers in the collaboration. The facility takes X-ray snapshots of atoms and molecules at work, providing atomic resolution detail on ultrafast timescales to reveal fundamental processes in materials, technology and living things. Its snapshots can be strung together into “molecular movies” that show chemical reactions as they happen.

In Razib’s #LightSourceSelfie, he takes you into the Near Experimental Hall and describes the stunning equipment that is used to undertake the experiments, the science it enables and the possibilities for new science with the upgrade to LCLSII. Razib says, “The best thing about working at a light source is the ability as a user to tap into the enormous scientific resources and experience that exists among the staff and scientists. Not to mention the state of the art instrumentation that you have access to, to realise your science. To my younger self, I would say, keep studying quantum mechanics, someday you will get to play with those electrons.”

To learn more about LCLS, visit