Saturday, July 11, 2009

Polyethylene demands some respect!

I recently found a link to this blog on why it is so hard to model even simple-looking polymers by Eric Drexler through Guru.

Having spent about a third of my life trying to figure out the rheology of polyolefins (like polyethylene and polypropylene), it feels nice that someone normally associated with a red hot topic of nanotechnology, acknowledges how hard it is to model these systems. He says:

At room temperature, polyethylene forms a disordered structure consisting of of small crystallites threaded by multiple, partly-folded chains. Under increasing tension, chains unfold and slide, distributing tension unevenly and breaking in more-or-less random patterns. The mechanical properties of the material (for example, stress-strain curves and maximum elongation to failure) depend on polymer chain lengths and processing history: both milk jugs and plastic bags are commonly made of polyethylene, but so is Dyneema, a polyethylene material in which the same repeating units — but in longer, highly oriented chains — form fibers that rival high-strength steel.

None of this is really news. Fresh students of polymer physics learn this pretty quickly. Disorder and multibody effects can make seemingly trivial systems become extremely complex and hence interesting.

Nanotechnology, really does have the potential to revolutionize the way we live, and as a scientific calling, there are few things more important than that.

However, like many trendy things, the hype is much bigger than the substance. I know, because I worked in the field for two years, and even now, dabble occasionally. If you look at scientific literature, about 80% of it should be recycled as toilet-paper (including perhaps some of my own work). Even prestigious journals like Science and Nature are constantly beguiled by SEM and AFM images, which reveal nothing important. I'll stop my rant right here, because I think it is a separate post in itself.

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