Something that is not reactive to lesser wavelengths of light, specifically IR.
You mean "monomer" or "oligomer" not "polymer." You are making the polymer by polymerization or crosslinking. UV-curing optical adhesives. You choose nice (mix of) free radical-cure monomers, then dissolve a photoinitiator like camphorquinone, a diarylketone, a benzoin ether, or a benzil ketal. The molecule fragments to free radicals after absorbing a UV photon. That sets off the polymerization. Exclude oxygen (triplet diradical quench). Cage recombination of the intiator is your enemy.
A microwave-pumped electrodeless mercury bulb the size of your finger can output a kilowatt of UV. Beware of pinholes in your irradiation chamber, including entry and exit if continuous. And now, a second of silence for the Trommsdorff effect.
If you want a polymer as such to do be photoactive, then something like Prog. Polym. Sci. 28 729 (2003). Pull it up in a university library to get the graphics.