Monday, November 05, 2007

Negative Intrinsic Viscosity and Positive Intrinsic Viscosity

A recent comment on an older post raised a good question: can intrinsic viscosity be negative?

Surprisingly, it can. I'm not up on that area, but there are a 17 Google Scholar hits for "negative intrinsic viscosity" and many are published in good journals, so it seems to be real. Or as I would argue, the data is reproducible. But as always in science, it interpreting the results that is the challenge.

I haven't read any of the articles yet, so here's my big chance to insert my foot in my mouth. I will start collecting the references and will post what I learn, so public humiliation is a real possibility here. My guess is that the polymer is breaking up some sort of weak network in the solvent (hydrogen bonding, polar-polar interactions...) so that the solvent has a lower viscosity, thus leading to the negative intrinsic viscosity - and the need for a new theory to explain it. Yes, go with a new theory since the old theory made a certain set of assumptions that are no longer valid.

That said, I am now wondering of the possibility of this effect happening in reverse but not being noticed. i.e., the polymer forces more hydrogen bonding or what have you that would lead to the solvent having a higher visocosity, but because the polymer is also leading to a higher solution viscosity, this "addition" is not noticed since it's easy to just explain the viscosity increase strictly to the polymer. How could you determine this?

First steps first: to the literature. As is often stated, 6 months in the lab will save you an afternoon in the library.

Friday, November 02, 2007

Use and abuse of "Organic"

Oh, the ever changing meanings of "organic". More important than the definitions of "organic" are the connotations of goodness and naturalness. The large disparity of the meanings can be seen by looking at the number of terms required to mean the "opposite of organic": inorganic, synthetic, commercial, nonorganic,...

Chemical Plants and Used Cars

Ineos is now the third largest chemical company in the world, although it's all been via acquisition instead of "organic" growth. Plastics News (subscription required) had their cover story last week (10/29)on the CEO, Jim Racliffe. Besides the usual filler, he made an unusual comment on chemical plants around the worlds: "Purchasing a German plant is like buying a second-hand Mercedes that has been really cherished by it's owner...Buying a plant in the U.K. can be like buying a second-hand Rover, while an Italian one can be like a second-hand Fiat and a French one can be quirky like an old Renault." No mention of American plants.

It's refreshing to see the emphasis on maintenance.