Photodegradable polymers

Photodegradable polymers (plastics) are especially designed in order to control their degradability when exposed to sunlight in the environment. Their main applications are in the solution of the following problems  

These functional groups can be incorporated into the polymer backbone either as carbon monoxide or vinyl ketones, but as with the biodegradable polymers, the rate of degradation in the environment is slow. Furthermore, in covered landfill sites where the materials would be deprived of light, air and water, the rate of degradation would be very slow. 

PA Polyamides (nylon 6 nylon 6,6 nylon 10 nylon 11 nylon 12) 

Plastics Making the Most of Our Resources, Association of Plastics Manufacturers in Europe, Avenue E Van Nieuwenheuyse 4, Box 3, B-1160, Brussels (1993). 

Source Statistics Handbook (1993 edn), British Plastics Federation, UK (ISSN 1351-5594). 

Stillwell, R.C. Canty, P.W. Kopf and A.M. Montrone, Packaging for the Environment A Partnership for Progress, American Management Association, New York (1991) (ISBN 0-8144-5074-1). 

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Topochemical [24-2] photoreactions of diolehn crystals has been reviewed. The reactions clearly depart from typical solution chemistry crystal-lattice control offers a unique synthetic route into photodegradable polymers, highly strained [24-2] paracyclophanes, stereoregular polymers, and absolute asymmetric synthesis. However, achieving the desired type of crystal... 

Hill, C.A.S., etin, N.S., Quinney, R.F., Derbyshire, H. and Ewen, R.J. (2001). An investigation of the potential for chemical modification and subsequent polymeric grafting as a means of protecting wood against photodegradation. Polymer Degradation and Stability, 72(1), 133-139. 

A few reports of pyrazine monomers have appeared in the literature (70Millloo). The most extensive study of pyrazine monomers involves their use to prepare photodegradable polymers <76MI11104). 2-Vinylpyrazine (145) copolymers and poly(2,5-distyrylpyrazine)... 

Another important consideration was the fact that the absorption maxima of oxime acrylate monomers could be tuned to the desired wavelength by the selection of desired ketone or aldehyde chromophore from whence the oxime was originally synthesized. In our design, UV photocrosslinking followed dye-sensitized visible polymerization which formed a soft gel. It is very important to be able to choose the absorption window for the crosslinking reaction to prevent interfering absorption, if any, from the residual dye initiator. Acyl oximes as part of the backbone of a photodegrading polymer chain have been studied by Smets [217],... 

EB Second, control over the rate of degradation is necessary. Not all consumer items made of a photodegradable polymer would be stored or used under the same conditions. Some of them might begin to degrade prematurely, causing inconvenience or even safety concerns. 

Ishikawa and co-workers (50, 51) have also reported the photodegradation of backbone disilane polymers (Scheme III). In this case, as in the previous example with pendant silyl substituents, silicon-silicon bond homolysis to produce silyl radicals was the predominant process. When irradiated in toluene, the photodegraded polymer showed a substantial -SiH band at 2150 cm in the IR spectrum. Similarly, NMR spectroscopic examination of the irradiated polymer showed evidence of silyl radical substitution into the solvent toluene. Irradiation of the polymeric disilane in deuterated methanol produced no bands due to Si-D in the IR spectrum and resulted in the incorporation of the elements of methanol into the chain ends (as revealed by NMR spectroscopy). For the phenyl-substituted polymer, the NMR evidence indicated that <5% of rearranged cyclohexadiene derivatives were formed. 

The grafted polymer is soluble in the alkaline ph-12 developer. The unexposed phenolic resin protected by the insoluble napthoquinone diazide is unaffected by the developer. Since the polymers are photosensitive to 5500A , they could eventually be useful spinoffs as photodegradable polymers soluble in alkaline soils. 

HUDGiN AND ZAWADZKi Additive System for Photodegrading Polymers 291... 

HUDGiN AND zAWADZKi AddUivc System for Photodegrading Polymers 295... 

Approximately half of the papers in the book deal with photopolymerization reactions including the role of photoinitiators and photosensitizers. The other half of the papers deal with photodegradation reactions including the use of photostabilizers and photodegradable polymers. 

Inspection of fracture surfaces of photodegraded polymers often reveals the presence of a smooth brittle zone near to the surface and a much more ductile fracture in the interior. The brittle zone depth often corresponds to that of the highly degraded depth obtained by FTIR or molecular mass measurements. 

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