Molecular Mimicry: Plastic, Steel Line Up Like Kin Scientists may have found a fundamental property of nature: Some plastics and some stainless steel materials seem to share a similar structure at the molecular level. Humble marshmallows, coffee stirrers and pingpong balls played a crucial role in the research.
NPR logo

Molecular Mimicry: Plastic, Steel Line Up Like Kin

  • Download
  • <iframe src="" width="100%" height="290" frameborder="0" scrolling="no" title="NPR embedded audio player">
  • Transcript
Molecular Mimicry: Plastic, Steel Line Up Like Kin

Molecular Mimicry: Plastic, Steel Line Up Like Kin

  • Download
  • <iframe src="" width="100%" height="290" frameborder="0" scrolling="no" title="NPR embedded audio player">
  • Transcript


OK, here's the exciting thing about working here at NPR. Somebody comes to you like NPR Science Correspondent Joe Palca.


Great guy; smart, smart guy.

INSKEEP: Oh, definitely smart guy. In fact he's all excited about this incredible story. He says this is the story about the discovery of a Frank- Kasper sigma phase in sphere-forming block co-polymer melts.

MONTAGNE: Are you done. What?

INSKEEP: It's a Frank-Kasper sigma phase in sphere-forming block copolymer melts. Let's let Joe explain.

JOE PALCA: Bear with me on this, because it's a really cool story. So to start, don't think about Frank-Kasper sigma phase sphere-forming block co-polymers.


PALCA: Think about a ping pong ball. Frank Bates uses them all the time.

MONTAGNE: Our other favorite tool - are marshmallows and toothpicks or coffee stirrers. Very low-tech as far as the visualization goes.

PALCA: Bates is a chemical engineer and materials scientist at the University of Minnesota. He uses these marshmallows and ping pong balls to make Tinker Toy-like models of the molecules he's studying. These molecules are block co-polymers. They're a kind of plastic. The co-polymer part means they're made from two different plastics, the end product having the best properties of both - for instance, new plastics that can be disposed of easily.

MONTAGNE: We had synthesized these molecules, and wanted to understand how they organized themselves down at that molecular scale.

PALCA: So he and his students shined a powerful beam of X-rays on them.

MONTAGNE: We found something that was simply inexplicable.

PALCA: They had a shape that no one had ever seen in a plastic before. Bates says part of the explanation seems to be related to the ingredients he used to make his plastic molecule.

MONTAGNE: There's one part of the molecule that doesn't like the other part.

PALCA: So the one part of the molecule folds up into a sphere, forcing the other part to the outside, where it makes little tendrils.

MONTAGNE: It's kind of a hairy sphere.

PALCA: The X-ray pictures of the particular block polymer Bates was studying - and in case you're interested, it was a mix of poly isoprene and poly lactide and poly styrene, poly isoprene and poly ethylene oxide - anyway, those X-ray pictures suggested something unusual was going on.

MONTAGNE: There was some new way of arranging our spherical - our hairy, spherical particles.

PALCA: Now, here's where the ping pong balls come back in.


PALCA: You can use them to study how spheres pack together. I brought some to the studio when I interviewed Bates. He was impressed, but not that impressed.

MONTAGNE: What you don't see, and you don't have there, is the ping pong ball with the pipe cleaners that are festooned around the ping pong ball, which create this image of a soft, squishy, hairy sphere.

PALCA: You need ping pong balls and pipe cleaners to get a real sense of how soft, squishy, hairy spheres of block co-polymers fit together. And as he reports in the journal Science, it turns out the way Bates' spheres fit together resemble nothing so much as something called the Frank-Kasper sigma phase. This is just a name for how the spheres pack together. It's never been seen in plastics, but it has been seen in some common metal alloys like stainless steel, and certain forms of uranium. So how is it that a plastic resembles uranium? Bates has an answer.

MONTAGNE: I think what this work does, is that it makes contact with something that is more universal than just plastics. It has the capacity to teach us how nature works. And you know, ultimately, that's my job - is to do that.

PALCA: Joe Palca, NPR News, Washington.

INSKEEP: Rewriting the movie "The Graduate" - I've got one word for you, young man, one word: Frank-Kasper sigma phase sphere-forming block co-polymer melts.


INSKEEP: This is NPR News.

Copyright © 2010 NPR. All rights reserved. Visit our website terms of use and permissions pages at for further information.

NPR transcripts are created on a rush deadline by Verb8tm, Inc., an NPR contractor, and produced using a proprietary transcription process developed with NPR. This text may not be in its final form and may be updated or revised in the future. Accuracy and availability may vary. The authoritative record of NPR’s programming is the audio record.