Where do I buy a sample of a certain exotic polymer?

Often people ask where to get a sample of some polymer that is not available from the usual places such as Sigma-Aldrich.

Here is a list of the best places I know of to find unusual monomers and polymers:

http://www.polysciences.com/shop/

http://www.scientificpolymer.com/index.asp

http://www.monomerpolymer.com/

This last one has a particularly good selection of block copolymers:

http://www.polymersource.com/