Polymer Modifications to Facilitate Biodegradation

By using this procedure several different types of otherwise all-carbon chain polymers have been prepared, and after hydrolysis to their low molecular weight carboxy- and hydroxyl-terminated oligomers, the latter can be degraded by fungal attack. 

The other principal approach, the preparation of a photodegradable copolymer, also utilizes a free radical copolymerization reaction, but in this case the comonomer is one which will create a ketone group either in the main chain 

On irradiation with ultraviolet light, the activated ketone groups present can take part in two different types of free radical, bond-breaking reactions. In organic photochemistry, these two reactions are referred to as Norrish I and Norrish II Reactions, and their mechanisms are shown below for the degradation of copolymers of ethylene and carbon monoxide [46, 47]  

Another method for photodegrading polyethylene is to include metal salts, which catalyze photooxidation reactions, in the solid polymer. The compounds most generally used for that purpose are divalent transition-metal salts of higher aliphatic acids, such as stearic acid or dithiocarbonates or acetoacetic acid. The photochemical reaction is an oxidation-reduction reaction that forms free radicals capable of reacting with polyethylene, RH, to initiate an autooxidation chain reaction, as follows  

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