Carbon chain polymers, biodegradable

Unsaturated carbon-chain polymers e.g. the polydiene rubbers discussed above) are very susceptible to peroxidation and hence biodegradation. Some of these have been studied as photodegradable polymers in their own right. For example 1,2-poly (butadiene) is a plastic with properties similar to the polyolefins. In unstabilised form it photo-oxidises and thermooxidises rather too rapidly to be very useful commercially. 

Although there has been much activity to produce totally biodegradable water-soluble polymers for a variety of applications, especially for detergents, few complete successes have been registered beyond poly(vinyl alcohol), poly(ethylene oxides), and poly(aspartic acids). Almost aU efforts to obtain carbon chain polymers that are completely biodegradable have failed, at least in the short-term testing protocols currently in use. Some promising leads are noted in condensation polymers, polyaspartic acids, and acetals and in the modihcation of natural polysaccharides. 

A good deal is now known about the kinetics of abiotic peroxidation and stabilisation of carbon-chain polymers and it is possible in principle to extrapolate to the time for ultimate oxidation from laboratory experiments. As already indicated, the key determinant of the time to bioassimilation is the antioxidant and if this is chosen to optimize the service life, bioassimilation can also be achieved as in the case of wood, straw, twigs, etc. It seems that straw is a particularly appropriate model for the biodegradation of the polyolefins since, like the polyolefins, it fully bioassimilated in biologically active soil over a period of about ten years. The most important conclusion from recent work is that nature does not depend on just one degradation mechanism. Abiotically initiated peroxidation is just as important, at least initially as biooxidation. 

Oxo-Biodegradable Polyolefins Carbon-chain polymers Hetero-chain polymers... 

The above discussion allows us to conclude that the bioassimilation of synthetic carbon-chain polymers has much in common with that of their natural analogues (notably natural rubber, resins and lignin). In all cases, nature uses abiotic oxidation chemistry together with biotic chemistry, very often together. The degradation products formed by oxo-biodegradation are of benefit to the agricultural environment as biomass and ultimately in the form of humus. 

Poly(vinyl alcohol), commercially available by the hydrolysis of poly(vinyl acetate), is probably the only carbon chain polymer widely accepted to be fully biodegradable in the environment, particularly in waste-water treatment facilities, and confirmed in current standard tests. But, even in these laboratory tests, acclimation is... 

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