Aug 19 2021Reviewed by Alex SmithA discovery by researchers from the University of South Florida (USF) together with collaborating institutions throughout the world could set the stage for better products, like enhanced batteries, cellphone screens and automobile paint.
Illustration of the creation of interfacial transient elastomer domain at the surface via the segmental dynamic gradient, employing representative simulation snapshot (rendered in VMD37). The exponential gradient in activation barriers to relaxation is illustrated by the color gradient of background beads; a representative chain spanning from the surface to the mid-film is highlighted in yellow. This gradient-spanning strand produces the transient surface rubbery behavior. Image Credit: University of South Florida.Upon zooming in on several advanced materials, like those in some of the newest batteries made of glassy polymers, including several plastics, one can find they are not even. Rather, they appear like a tie-dyed shirt, with swirls of various materials.
The researchers feel that this “nanoscale structure” could offer exceptional properties since the surface of glassy polymers is not tough, but exhibits a rubbery consistency.
A new study reported in the journal Nature transforms how one could comprehend the behavior of glass, which is a state of matter, including the features of liquids and solids.
Scientists at USF in collaboration with Princeton University and Zhejiang Sci-Tech University have found that a natural effect takes place at the surface of glassy polymers. This creates a compliant rubbery layer that is only a few dozen atoms thick with properties that vary completely from the rest of the material.
This behavior finds extensive technological implications, showing how glassy polymers could stick to each other and potentially offer an understanding of scratch resistance at the molecular level.
This gives us the ability to understand and control how glassy polymers – plastics – behave right at their surface. Whether it’s a particle of dust sticking to paint, two fibers sticking together in a 3D printer, or abrasion at the surface of a pair of a plastic lens in your glasses, this microscopic layer at the surface of plastics is immensely important to how these materials perform, and now we really understand its nature for the first time.
David Simmons, Study Corresponding Author and Associate Professor of Chemical, Biological and Materials Engineering, University of South Florida
This breakthrough was made by Simmons and his collaborators by developing “wetting ridges,” minute ridges at the plastic’s surface. This is done by discharging an ionic liquid droplet on polystyrene surfaces at different temperatures. Polystyrene is solid plastic and a kind of glass that is naturally clear and is used for building materials, consumer products and food packaging.
By employing these measurements and by zooming in to the molecular scale with supercomputer simulation models, the researchers disclosed the existence of this soft, rubbery layer and how it could be regulated. This discovery could denote the finding of the “sweet spot” for essential properties like adhesion and scratch resistance, even on rigid surfaces.
The theory appears to be equivalent to the existing understanding of what makes ice skating feasible. The rink’s top molecular layer acts like water, even if the rink is frozen. This enables skates to glide over the surface; otherwise, it would not be possible.Journal Reference:
Hao, Z., et al. (2021) Mobility gradients yield rubbery surfaces on top of polymer glasses. Nature. doi.org/10.1038/s41586-021-03733-7