A discussion of the major mechanisms for electronic energy transfer for organic molecules is presented. Application of the techniques and ideas of electronic energy transfer to study the properties of polymers is given.

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Energy Transfer Processes

Uses of the fries rearrangement for the preparation of hydroxyarylketones. a review

Amines constitute a family of stabilizers protecting plastics and coatings against free radical oxidative degradation and diene based elastomers against both ozonation and oxidation. The respective antioxidant, antifatigue, photo-antioxidant and antiozonant protection of polymers is dependent on the structure of the particular amine. Mechanisms of specific contributions of aromatic and heterocyclic amines have been interpreted in detail. The data are based on up-to-date knowledge of the inherent chemical efficiency of individual aminic types and the physical factors governing the final effect. Application of polymer stabilizers is mandatory from the technical point of view. The public concern dealing with the potential impact on the environment is increasing. Therefore, the final part of the paper is devoted to environmental aspects encountering amine stabilizers.

Aromatic and heterocyclic amines in polymer stabilization

Although a wide range of aromatic polycarbonates has been synthesized and examined [1–3], the term polycarbonate usually refers to the commercially available poly[2,2-propane-bis(4-phenyl carbonate)], i.e., and this polymer is discussed exclusively in the present review. Polycarbonate possesses a number of attractive mechanical properties [1,3] e.g., high impact strength, high elastic modulus, and creep resistance. These features, coupled with the fact that the polymer is almost unaffected by water and many inorganic and organic solvents, permit its use in a variety of applications. In such applications the mechanical properties may alter with time because of the viscoelastic nature of the material.

Stability of Polycarbonate

The rôle of oxygen in the photo-ageing of bisphenol-A polycarbonate

The influence of free, diffusion-control quenchers of triplets (naphthalene, biphenyl, 2,5-dimethyl-2,4-hexadiene) on the photolysis of poly(vinyl phenyl ketone) in benzene solution has been investigated. The Stern-Volmer plots for quenching of main-chain scission were linear, and the quenching constants were independent of the macroviscosity of the solutions. Copolymers of vinyl phenyl ketone with 1-vinylnaphthalene and 2-vinylnaphthalene containing as much as 10% (by weight) vinylnaphthalene were prepared. The photolysis of the copolymers was compared with the photolysis of poly(vinyl phenyl ketone) in the presence of free naphthalene. It was found that the quenching efficiency of found naphthalene units was about 21 times higher. The possibility of migration of the absorbed energy along the polymer chain is discussed. The relation between average-number molecular weight Mn and intrinsic viscosity [η] has been determined osmometrically. For unfractionated poly(vinyl phenyl ketone) in benzene at 30°C, the relation [η] = 2.82 × 10−5Mn0.84 has been found.

Zdeněk Maňásek

Papers

Influence of free and copolymerized triplet quenchers on the photolysis of poly(vinyl phenyl ketone) in solution

Photoinitiated rearrangements in poly[2,2-propanebis(4-phenyl carbonate)]

Stabilising effect of monomers, homopolymers and copolymers of vinyl derivatives of sterically hindered amines on the photo-oxidation of polypropylene

E.S.R. study of alkaline, oxidative degradation of saccharides. Identification of 2,5-dihydroxy-p-benzosemiquinone

Photoumlagerung und Photoabbau des Poly(4-benzoyloxystyrols) und Poly(p-kresylacrylats)