Monday, July 27, 2015

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:
    Relay polymerization
    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:
Trigger polymerization
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


Joe Q. said...

Thanks for the tip -- it's a nice bit of chemistry. Hawker is a clever and creative guy.

I just wish that olefin methathesis-based chemistry were more accessible to industry -- there are some major hurdles to implementing it on a commercial scale.

John said...

I agree. Lots of potential, but I'm not aware of any industrial applications.

Anonymous said...

I hate to give an answer perceivable as wishy-washy, but it's really dependent on context, and the hypothetically similar situations described at the beginning are not really that similar.
There are some situations that arise where reading the review is of import because:
1) It saves time relative to reading the original article (or book) - this is particularly important if you're having to do a broad literature review and are fishing for relevant materials, and need to quickly create "Reading Queue" and "Don't Bother" piles; or if your time to get up to basic comprehension speed on the topic is too limited. This is not a substitute measure for reading the article if it's determined to be of interest. Yes, this is what abstracts can also be used for.
In other contexts, I'm sure you're aware of pay-for-synopses services; I suspect frequently they are crutches for the terminally lazy and mentally challenged, but there are more valid rationales for their existence.
2) Sometimes the reviewer is in a better position to evaluate the importance/significance/validity of the research or is better able to articulate and contextualize the research than either you or the original investigators/writers can.
3) On some occasions the review may be more important than the article. Occasionally reviews are used as springboards to introduce new approaches or applications to the same issue. Sometimes they have turns of phrase which are valuable in assessing the related issues or which may "spark" lines of thought that the original research might not. Sometimes they can introduce other relevant materials of which you may have been unaware.

Anyway, that's three possible sets of reasons why one might want to pay for a review rather than read the article itself. My bias would be to read the freely available material, but then again I have also been criticized for being too willing to "buy the books" and "over-research" things in general.

To sum up, I guess overall the decision process for this broadly involves:
1) time context;
2) usage context;
3) relevance context.