Intentionally Making Polymers Photodegradable

Some polymers are intentionally designed to degrade when exposed to light. There are two basic methods for doing this. One method is to incorporate a chro-mophore into the polymer chains. For example, deliberate incorporation of carbonyl groups leads to light-sensitive polymers, as in the commercial Ecolyte polymers. These polymers are made by copolymerizing vinyl ketones with vinyl monomers 

Radical production and/or backbone degradation occurs by the Norrish types I and II routes in these polymers (scheme 6). 

An alternative strategy for incorporating CO into vinyl polymers is to copolymerize vinyl monomers with CO, thereby incorporating the CO directly into the polymer backbone. This approach, used commercially with ethylene, yields polymers with structures like that shown in scheme 3. Degradation is by the pathways indicated in that scheme. Note that once radicals are introduced into the system, chain degradation can occur by the auto-oxidation pathway and the subsequent backbone cleavage reactions. 

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