A Sweet Ring-Opening Polymerization Scheme

Before I get to today's polymers, let me ask you a few questions:

• If you could see a movie for free or pay to get a review of the movie, which would you choose?
• If you could eat a restaurant for free, or pay to get a review of the restaurant, which would you choose?
• If you could go to a concert for free or pay to get a review of the concert, which would you choose?

Hold your answers until later when the motivation for them will become clearer.

There was a polymer chemistry paper published last month in the Journal of the American Chemical Society (JACS) that brings two separate ideas together to produce some novel polymers.

1. Ring opening polymerizations proceed best when the ring is small in size and has some strain built in to help the reaction along. Epoxies, being a three-member ring are a great example of this, capable of reacting at room temperature or below. (Many epoxies are shipped on dry ice). But smaller rings offer only a small choice in what will end up in the back bone. Larger rings offer more options, but greatly reduced reactivity.
2. A recently developed ring-opening methathesis polymerization (ROMP) is called relay polymerization and is illustrated here:
   
   In the enyne starting material, the triple bond moves to the left to form the five-member ring found in the product and at the same time opens the six-member ring up for polymerization.

The authors combine both of these concepts to produce polymerizations such as this:

While ROMP polymerizations are well known, they have always had restricted chemistries until now:

"For the first time, polymers with arbitrary functionality (ester, amide, sulfonamide, aliphatic, aromatic, heterocyclic, etc.) within the backbone can be produced while still providing control over molecular weight and molecular weight distribution."

Having esters in the backbone means that this material could be hydrolytically degraded. While such degradation is most often undesirable, at other times, it can be a blessing. Regardless, just having it as an option is helpful.

And this polymerization is extra sweet as the trigger is built using saccharin as a starting material. All in all, very clever.

I need to mention that the article is open access. Anyone can read it for free. But if you try and read a review of it at Nature Chemistry, you have to pay. So, one last question:

If you could read a research article for free or pay for a review of it, which would you choose?

(Shameless self-promotion: my article reviews have always been and always will be free.)

Previous Years

July 27, 2012 - The Most Overlooked Analytic Technique in Polymers - DSC

July 27, 2011 - Bad Management or Excellent Engineering?

July 27, 2010 - Gelators - Part I