Friday, May 16, 2014

The New Wonder Polymer

A novel family of polymers is featured in Science today. The polymers have an interesting range of properties, but as you might expect, they have been hyped far beyond recognition. The research paper is a mess. There is way too much material jammed into a small space, all of which makes it difficult to understand exactly what is being discussed. The wording is loose and imprecise as well. This furthers confounds the confusion that the mainstream media is picking up on.

Let me start with the good stuff. A number of different polymers were prepared, all by reacting a diamine with paraformaldehyde:
This is figure 1.B. (I'll talk about 1.A in a minute.) As you see, there are a series of two reactions. The first forms the HDCN, while the second shows that upon further heating, another polymer network (PHT) forms. The networks have a good Young's modulus of about 7 GPa for the HDCN and about twice that for the PHT. They also show that if the diamine is an amine-terminated polyethylene glycol, the resulting HDCN is a organogel that self heals. Lastly, the PHTs are stable for a pH > 3, but at a pH of 2 or less, they depolymerize to the monomers.

As I said, all good stuff. I don't know that it is really worth reporting in Science, but that is open to debate about most articles in there. It's pretty tough to fill a journal like that with truly groundbreaking research every week. (Ditto for Nature.)

Now for the criticisms of the paper. First, figure 1.A adds nothing to the report. It only shows the same reaction as in 1.B, but with small molecules. I never seen something so elementary in any polymer chemistry paper before. It is kinda shoehorned into the report via figure 2, which shows the results of some computational chemistry on still other small molecules showing the mechanism for the reaction.

Having a thermoset that can be depolymerized is nice as that is often quite challenging. But when the article entitles this as "recyclable", then that's a step too far. Soaking a polymer in strong acid, then purifying the monomers only to then repolymerize the polymer matches nobody's definition of recycling. At least the commentary in the same issue by Long got it correct by calling it pH reversible.

And as I mentioned before, this is all a jumble of work thrown in together. You have multiple polymers being prepared with radically different performance characteristics and some computational results as well for good measure. No wonder the mainstream media is really botching the coverage. Consider this remark on Twitter: "Using computational chemistry, IBM researchers discover a new polymer. #ComputingRocks" (@Grady_Booch). No they did not compute the new polymer, but only used the computations to understand the reaction mechanism after the polymerizations were already discovered.

It gets worse. Pieces are hailing this as Scientists Discover First New Polymers in 20 Years. Rest assured, I've have discovered many new polymers in this same 20 year time interval as have thousands of other polymer chemists. This also raises the question of what was that last "new"polymer discovered 20 years ago. I have no idea.

And then there is this: IBM researchers discover new polymer materials that are stronger than bone and can heal themselves. Yes, but not at the same time. You can have the stronger the bone option or you can have the self heal option, but not both. Again, too much material was jammed into this small space and little was done to clarify matters. And since IBM's PR machine is always welled oiled and fully functional, we can plan on hearing about this for weeks to come.

Previous Years
May 16, 2013 - Buy & Selling Division in the Polymer Industry

May 16, 2012 - Time to Test My Beliefs

May 16, 2011 - Updating the Blogroll

May 16, 2011 - Definitely Updating the Blog Roll


Polychem said...

Thanks for clarifying this for me. I've seen the hype, but haven't had access to the article for the details.

Anonymous said...

yes, i totally agree that this Science paper has a lot of mistake and hype in it. very misleading. Amine and HCHO reaction is well known. computational chemistry is rubbish as well.