New Plastic Liquefies Under UV Light but Then Resolidifies

I would describe myself as an organic chemist, but part of my training and experience involves polymers (also known as plastics). It’s just part of the territory. Plastics are nothing more than long chains of organic material, joined together (end to end) to form a strand. Cellulose is one example of a polymer. It’s nothing more than thousands of individual glucose molecules, linked end to end to form a long chain. The bonds between the glucose molecules are very stable and it takes some fairly sophisticated chemistry to break them apart.

Plastics can be designed to be fairly resilient to injury. We have impact resistant plastics, for example. However, once plastic is scratched, there’s not much that can be done. You can fill the gap with some type of filler (maybe some type of plastic goop, which will dry and then you can use some sandpaper to smooth it out), but there really aren’t that many options. The scratch certainly isn’t going to fix itself. Well, all that has changed.

Researchers from Switzerland report in the journal Nature (arguably the world’s top scientific journal) that they have designed a new type of polymer. Instead of linking together solely organic units, they periodically mix in special functionalized metals. Their material could be more accurately described as a metallo-polymer. The reason for the inclusion of the metals becomes obvious when you realize that the organic-metal bond is not stable under ultraviolet light. UV light shatters all of the organic-metal bonds, leaving the material no longer a polymer (made up of an unbroken chain of units) but instead a liquid pile of monomers (the individual organic units and metal molecules). If the UV light is then removed or turned off, everything goes back to the way things were before. The organic units hook up to the metal units. The polymer reforms itself. This is made possible by the chemical affinity that the two units (organic and metal) have for each other. They really want to be bonded together, but they just can’t keep that handhold if they’re being irradiated with UV light.

The applications for this are enormous. Look around you and count the number of objects that are plastic. Would you want to repair some of these objects if they were damaged?. Imagine a microscopic invisible film of this material on top of car paint. Did someone scratch your car? Not a problem – shine a UV light (cheaply available from scientific supply companies or Ebay) over it for a few seconds, and then take the light away. The surface layer of this new material will “melt” (more accurately, it will depolymerize into a liquid mixture of monomers), and the liquid will fill in the gap of the scratch. Once the light is gone, it “hardens” (repolymerizes) and the problem is solved.

The source of this article can be found at:

Mark Burnworth, Liming Tang, Justin R. Kumpfer, Andrew J. Duncan, Frederick L. Beyer, Gina L. Fiore, Stuart J. Rowan, Christoph Weder. “Optically healable supramolecular polymers”. Nature, 2011; 472 (7343): 334.


People also view

Leave a Reply

Your email address will not be published. Required fields are marked *