Tuesday, September 21, 2010

Polymers in Space - Part II

There was another set of polymer experiments run in space that I am aware of, these dating back to the 1990's. Like the previous post in this subject, the experiments involved polymerisation. My first thought of hearing about the experiments was to question why they were run at all. I certainly could not imagine that gravity could play any impact on a polymerization at all. I was wrong. A couple of NASA engineer wrote a nice summary of the experiments (open access) that quite readable.

Thermal gradients, density gradients and composition gradients can all lead to convection cells in a normal situation, but can pretty much negated while in orbit. [*] While these can all be overcome by effective mixing, their study is still worthwhile. During compolymerization, these gradients (or more correctly, some effects of these gradients) can end up being locked into the final product - with differing ratios of the comonomers being spatially resolved. These differences can be rather important in certain situations.

A commercialized example of this are the contact lenses developed by Paragon Vision Sciences. Differences in comonomer composition will lead to differences in refractive index and can make for some really bad corrective lenses. The work in outer space was able to identify monomers that were insensitive to polymerization while in the gradients.

[*] Some of the same results have been observed for polymerizations occurring either in a drop tower or on planes with parabolic flight profiles.

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