Question

how can you tell if a polymer has been made?

Answer 1

You can tell if a plymer has been made because it has changed its texture.

Answer 2

Sorry, meant to say polymer!

Answer 3

Depends what you mean. If you mean, how can you prove that what you have is a very long chain molecule in solution -- this is actually quite hard, and in the early days of polymer research (then called "colloidal science") the general assumption was that what was being formed were tiny solid particles suspended in a fluid medium (a colloid), and this is what gave the solution its peculiar viscoelastic properties. Staudinger's "macromolecular hypothesis" -- that such solutions contained macromolecules, giant molecules with hundreds of thousands of chemical bonds, was not immediately accepted.

You can readily measure apparent molecular weight by various physical chemistry means, such as measuring osmotic pressure, or low angle light-scattering spectroscopy. This is perfectly sufficient if you already know, or believe, that what you have in solution is well-solvated individual macromolecules. But if you don't know that, it is difficult to distinguish between macromolecules and tiny colloidal particles made of many smaller molecules aggregated together physically (not chemically).

The only completely sure-fire method of which I can think, to establish that you absolutely do have macromolecules, would be to cast a thin dilute film of them onto a surface, then do STM or AFM microscopy on them and directly image the molecules. Then you'd know for sure.