Friday, December 10, 2010

The Impact of Biology on Polymers

I'm very excited about what new polymers we will be able to make in the not too distant future. Not because chemists are devising new monomers, but because biologists are. I wrote yesterday about isosorbide and how a new polycarbonate can be made with it. Today's post is about a new polyester.

The basis for these materials are a genetically modified strain of yeast (Candida tropicalis) which is able to take normal fatty acid and pin a hydroxy group on the end of the saturated chain. The picture below is from the articles abstract where all the "X"'s in the diagram are existing biochemical reactions that needed to be stopped in order to have the desired output, and the only way to stop them was by genetic modification, no small feat I'm sure. You can certainly read the article (paid subscription) if you want, but the rest of my post is on what I see happening with the newly created w-hydroxy fatty acid.

The easiest reaction I can imagine would be for the material to create a self-condensing polyester - a head-to-tail combination that much like normal PET production produces water. What sets this reaction about is that normal PET is made from two monomers - ethylene glycol and terephthalic acid, while this could be made from just the single monomer. Depending on the length of the saturated carbons, you could imagine crystallinity developing to a certain extent. It could also be worthwhile to investigate the biodegradability of the new materials, as a shorter version of these, polyhydroxybutyrates are known to have this property. You also could also try reacting it with one or more additional diols to create a random copolyester.

I have no idea as to the economics of scaling up production of the these monomers - I certainly have some doubts just because it is new, but still, this post and yesterday's post should have you convinced that polymer chemistry will be undergoing a revolution at some point in the not-too-distant future. New materials with new properties, courtesy of some microbial life modified to meet our needs.


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