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

Thursday, July 23, 2015

Ocean Plastic Greenwashing

While the concern over ocean plastic continues to grow, a new threat associated with it that needs our more immediate attention: greenwashing. There is an ever growing list of companies and publicity-seeking celebrities that are trying to leverage this problem into cash in their pockets by giving the illusion that they are solving or helping to solve the problem.

Adidas is the latest to join in this hoax with an ocean plastic shoe. The Huffington Post has a nice takedown on this scam so I won't go any further. Just last week there was a Dutch engineering group that proposed making roads out of ocean plastic. Last year Pharrell Williams proposed making blue jeans from ocean plastic. Before that there was also the Elexctrolux vacuum cleaners (a grand total of 5 were made and were never for sale to the public), surfboards and the Method hand soap bottle. These are all the items that I am aware of, so there could be more.

The common thread through all of these is that the "Ocean Plastic" that they are using is really "Beach Plastic", plastic gathered on beaches while it is still in large pieces that have suffered minimal degradation.
Method's comments::
"The framework that we're using is that there are a number of beach cleanup organizations that work here in California and that work in Hawaii that are regularly cleaning up this plastic..."
And Pharrell said
"The PET bottles are collected from the coastlines after washing in from the ocean."
(Bottles that haven't washed out into the ocean will apparently be overlooked for this project.)

The reason that all these efforts are using Beach Plastic and not Ocean Plastic is that collecting ocean plastic and doing anything with it is (other than burning it as fuel) is not going to happen. This is what plastic in a gyre looks like:
Ocean plastic - as it really is
A view of an ocean gyre - see any plastic?
Tiny, tiny pieces of degraded plastic. The degradation pretty much ensures that even if recovered (How? Filtration would simultaneously collect a tremendous amount of living creatures from the ocean, arguably "killing the wildlife in order to save them"), the plastic would not be strong enough to make anything useful. Additionally, the recovered plastic would be a mixture of many types which would need to be sorted prior to recycling, something that cannot be done economically with such small pieces.

Sorry, but ocean plastic is going to remain as ocean plastic, and no company or celebrity should give you any impression otherwise. That is why prevention is to key. Plastic has no business being in the ocean, so do your part to make sure it doesn't end up there. Supporting these businesses in their greenwashing efforts is not part of the solution.

Previous Years

July 23, 2012 - Wrap-Up on the Nylon-12 Shortage

July 23, 2010 - A New Nano-Clay for Polymer Reinforcemen

July 23, 2010 - Isn't this Obvious??

Wednesday, July 22, 2015

Fairlife Followup

Last week I wrote the bottle that contains Fairlife chocolate milk and in particular about how confusing the recycling code at the bottom is. It's the number 7, but instead of saying "other" as it should, it says "PETE" (which corresponds to the number 1 code). I contacted Fairlife about this and received the following email:
"Hi John!

Thanks so much for reaching out; we REALLY appreciate your taking the time to get in touch with us.

Our bottles are primarily made from PET, which is #1 plastic. We add a very small percentage of white colorant to protect the milk from UV and visible light (UV and visible light impact the integrity of the milk and the vitamins present in it). The addition of the white colorant is what makes the plastic bottle #7. PET plastic and the white colorant are both approved by the FDA as safe for packaging food products. There is no BPA in any of our packaging.

If you have any other questions or comments, please do not hesitate to give us a shout!

All the best,

Consumer Affairs

fairlife® ultra-filtered milk"

(Glad to see that the exclamation point key on their computer works so well!)

This just doesn't add up. Adding white colorant to PET doesn't make it a number 7, just as adding any other pigment to any other plastic doesn't change the base polymer or its recyclability.

But I question the need for a pigment at all. While Brooke is correct that the white plastic will "protect the milk from UV and visible light", a white pigment isn't needed. The bottle is already mostly covered in a brown-colored overwrap film which will block light. Besides, "normal" milk is packed in high-density polyethylene (HDPE) which is a hazy white without any white additives. The whiteness arises from the crystals in the material scattering light (which coincidentally is also why milk appears white).

(As an aside, UV absorbers have been added to polyethylene milk bottles, but understandably, consumers are put off by the yellow color. This is hardly new technology, having been around since at least 1993.)

My guess: there is a barrier layer in the package which makes the whole mess incompatible with PET, and that the white pigment story is just a red herring.

Previous Years

July 22, 2011 - The Heat Index and Jenson's Inequality

July 22, 2010 - A Bio-based Acrylic

Thursday, July 16, 2015

Polymerization Dreaming

Chemists at the University of Arizona recently announced that they have experimental proof that ethylenedione, O=C=C=O, exists. It's basically two carbon monoxide molecules, C=O, butted together. The linked page will provide you more background about it; it's pretty interesting since the molecule has been theoretically proposed for quite some time, but since it falls apart in about half a nanosecond (literally) to two carbon monoxide molecules, you can't really plan on buying a gallon or two and doing something with it.

Too bad, as I would want to polymerize it. (No surprise there, huh?) All those double bonds are just screaming at me to be opened up and go chain forming. If you went for the C=C double bond, you would end up with what I am jokingly (or not) calling polydiacetyl:
poly diacetyl
Or maybe polypopcorn butter, since diactyl has been used for artificial popcorn butter flavoring. Polyketones - polymers with a carbon backbone and pendent ketones - do exist, but not like this. They are normally made by copolymerizing carbon monoxide and ethylene (and maybe some propylene), so there are far fewer ketones than what we would have here, hence the unique name to differentiate it.

But maybe having less ketones is a good thing.

The Wikipedia article on diacetyl states: "A distinctive feature of diacetyl (and other 1,2-diketones) is the long C-C bond linking the carbonyl centers. This bond distance is about 1.54 Å, compared to 1.45 Å for the corresponding C-C bond in 1,3-butadiene. The elongation is attributed to repulsion between the polarized carbonyl carbon centers." That's some intense repulsion to extend a C-C bond by 6%. But that repulsion then gives me a good idea of how the polymer would behave if it were ever made. Despite having a pure carbon backbone, the repulsion would force the chain into a fairly extended configuration, more like a liquid crystal than the random-walk globule so typical of most thermoplastics. So I would expect this to be pretty viscous when molten. While the polymer would have a pretty regular structure and could, at least on paper, seem amenable to crystallization, again, I think the repulsive centers would most likely resist such regular packing and so the material would likely be glassy as well.

Viscous and glassy and impossible to make. Not an ideal combination. I doubt I will ever have these guesses confirmed, but one can dream...

Previous Years

July 16, 2013 - The Added Dangers of A Fire at a Plastics Plant

July 16, 2012 - Rheology, Theology and Deborah

July 16, 2010 - No Death Knell for PVC

Wednesday, July 15, 2015

Plastic Roads

While I'm all in favor of plastics displacing traditional materials in most applications, I have some serious doubts about this one - a Dutch company, VolkerWessels, wants to replace traditional asphalt and concrete roads with plastic. And not just with a layer of plastic, but a construct that has a hollow inside so that pipes and other utilities can be run through it. Take a look at this concept drawing:
Plastic Road Concept Drawing
My immediate thoughts were how much this looks just like another picture that I recently discussed:
Morrison Bridge Cross Section
This is a cross-section of the infamous Morrison Bridge that was recently installed in Portland Oregon and has begun to fail very quickly.

Similarity in shape doesn't mean similarity in failure, but the article does little to allay my fears.
"VolkerWessels, is collaborating with the city of Rotterdam to start prototyping plastic-built roads in a “street lab” provided by the city...The idea is to recycle plastic from oceans into a tough aggregate that could be poured and molded into pre-fabricated “bricks” and installed on site quickly." (Emphasis added)
Ocean Plastic?!? Don't they know that nobody has an effective means to recover ocean plastic, certainly not on the scale that would be needed to make a road of any decent length? But since we are in the pre-prototype stage, you can dream all you want. Or at least until "the rubber meets the road" (sorry, couldn't resist) and the surfaces are tested. Somehow I think there will be lots of failures setbacks "learnings".
"VolkerWessels’...has years, even decades, of research and development ahead of it, if it survives."
Quite the understatement if you ask me.

Previous Years

July 15, 2014 - An Unlikely Combination: Thiol-Ene Chemistry and Isocyanate-Free Polyurethanes

July 15, 2013 - Closing the Door after the Horse has Gone Tilting at Windmills

July 15, 2011 - A New Polymer Blog

July 15, 2010 - Blow Molding on a Small Scale

Tuesday, July 14, 2015

Coincidences and Chicken Feathers

Coincidentally, I wrote just last week about how quickly the University of Illinois Alumni Association knew my new address. But yesterday, I got another piece of mail that also had not been forwarded, but instead had the new correct address. In this case, I was happy to see it, as it was from Patent Awards, announcing that a patent application of mine had issued. The company sells nice looking plaques for hanging on the wall with images of the first page of the issued patent. That's how it works in this country - the first time you find out about a patent issuing is not with an official government letter but when a company tries to sell you something. What was most shocking was that the patent had issued only last Tuesday. Was it possible that this company somehow in less than a week had seen the publication and also knew my new address? No, probably not. I looked at the file wrapper [*] on the USPTO Public PAIR website and saw that the notification for allowance was way back in early March, so they knew this was coming. Somehow they also knew my new address without me giving it to them, but I figure the Post Office probably sells that information.

The patent was from an application that I had filed back in 2012 when I was at Aspen Research. It involves the use of chicken feathers as a base for polymerizations. Chicken feathers are mostly a waste product that is largely ends up being buried. In the US alone, 4 - 5 billion pounds end up underground and so it represents a huge potential feedstock that is biobased and present around the world. That's at least 4 - 5 billion pounds of plastic that could be made, and more if the feathers are combined with other materials. We used to dream big and joke that the first 5 billions pounds would be free. After that:
Featherless chicken
"Eat more cowz!"
The feathers are about 90% keratin, a nasty crosslinked protein that, like most proteins, degrades upon heating before melting. The crosslinking is due to endless amounts of disulfide bonds. Attempts to plasticize them by solvating the disulfide bonds haven't worked out well in the past for a number of reasons. Being heavily involved in thiol-ene chemistry at the time, I was able to devise a scheme that worked with the disulfide bonds.

The Public PAIR website also showed that there was no office action - the patent sailed through unchallenged by the examiner. That's a first for me.

Coincidentally, I was just thinking about that chemistry yesterday before getting the letter. It's been a couple of years since I've worked with the stinky mercaptans, but it all came back when I read the latest installment of the Master Organic Chemistry blog on thiol reactions. James points out that mercaptans are analogous to alcohols in some ways (as would be expected), but not in others, particularly when undergoing oxidations. Alcohols are progressively oxidized to ketones/aldehydes and then carboxylic acids, while thiols are only oxidized to disulfides. I had never really given it much thought. Why aren't there -CSSH groups for instance? Apparently a C=S bond is rather unstable.

Update: As Joe Q. pointed out in the comments, dithiolcarboxylic acids (-CSSH) do in fact exist. A closer rereading of the James's post made it clear that thioketones and thiolaldehydes are what he was discussing, although they can be stabilized with an adjacent nitrogen or other functional groups, which was also mentioned by Joe Q.

[*] The file wrapper is an ancient term for all the paperwork associated with an patent application.

Previous Years

July 14, 2014 - A Novel Adhesive

July 14, 2010 - Chemistry and Music

July 14, 2010 - No RDA on BPA in the EU

July 14, 2008 - Accelerated Aging - Getting Bad Data Even Faster - 1st in a Series

July 14, 2008 - Playing the Building