polymers having photoreactive metal - metal bonds along the backbone of the polymer are disclosed , which bonds rendering the polymers photo - labile . metals participating in such metal - metal bonds are from groups vib and viib of the periodic table as well as nickel . each metal - metal bond is present in a cord group present in at least one monomer incorporated into the polymer . the core group also comprises carbonyl groups and an aromatic cyclopentadienyl group bonded to each metal atom . various organic and organosiloxane linker groups bonded to the cp groups render the core group - containing monomer polymerizable into a composition of matter having physical properties determined in part by the chemical composition and conformation of the linkers . reactions for synthesizing core groups , monomers , and various polymers therefrom are disclosed , including copolymerization reactions . upon exposure to light , the metal - metal bonds in the polymers cleave , effecting more rapid degradation of the polymer than by other processes normally present in the environment .