Main-chain cleavage

A significant part of our recent work with imaging systems which incorporate chemical amplification has involved the design of polymers which can undergo thermally activated multiple main-chain cleavages as the result of a phototriggered process. [Pg.101]

Imaging via Main-chain Cleavage of Polycarbonates. Polyesters and Polvethers. [Pg.101]

A definite number of main chain cleavages should occur in the soluble part of the film when a developer is specified and the least amount of photons required for the dissolution of the film in the developer used. If the definite number is K, the following formulae are obtained ... [Pg.289]

Spectral Dependence of the Absolute Quantum Yield of the Main Chain Cleavage Reaction... [Pg.291]

The high specificity of elimination of alkyl side branches from poly (olefin) s is attributed to (1) enhanced scission of C-C bonds at tertiary carbon atoms, reflecting their lower bond energies, and (2) a cage effect which produces geminate recombination of many of the main-chain cleavages, whereas the mobility of fragments of low molar mass enables them to escape. [Pg.144]

Scheme 1 shows the reaction which occurs when an aromatic polyester such as [I] is subjected to UV irradiation (5). The polymer first undergoes main-chain cleavage with subsequent rearrangement to polymer [II] which is photostable and can be used as a thin coating to protect efficiently other substrates which are normally photodegradable. [Pg.269]

Naturally Occurring Forms of Pancreatic Ribonuclease and Well-Defined Main Chain Cleavage Products... [Pg.670]

Development (O2 Plasma) Effective quenching of the excited states formed by photon, electron, or Ion impact Oxidative degradation Main chain cleavage in the excited state formed by photon, electron, or ion impact Oxidative degradation... [Pg.161]

The formation of propionic acid as the principal organic product of the radiolysis of acetylalanine implies that direct main-chain cleavage is involved as the major decomposition mode. We tentatively define the stoichiometry of this cleavage in terms of... [Pg.391]

Scheme 7.5 Light-induced main-chain cleavage of polyethylene containing traces of carbonyl groups.

Simultaneous cross-linking and main-chain cleavage of linear polymers I 193... [Pg.193]

Simultaneous cross-linking and main-chain cleavage of linear polymers 195 Table 7.3 Predominant effects upon UV irradiation of polymers in the absence of oxygen [27]. [Pg.195]

Scheme 7.15 Main-chain cleavage and cross-linking of polyacrylonitrile.

The lifetime of the excited state giving rise to main-chain cleavage is shorter than 100 ps [44]. [Pg.198]

In conclusion, the salient features of the light-induced oxidation of polymers are the formation of hydroperoxide, peroxide, and carbonyl groups, the latter in the form of both aldehyde and keto groups. Moreover, certain reactions, such as reaction (d) in Scheme 7.20 and reaction (b) in Scheme 7.21, result in main-chain cleavage as far as the oxidation of linear macromolecules is concerned. Main-chain cleavage leads to a deterioration in certain important mechanical properties. Therefore, the photo-oxidation of polymers is deleterious and should be avoided in commercial polymers. Appropriate stabilization measures are discussed in Section 9.3. [Pg.201]

Fig. 2. Proposed mechanism of degradation of PIB via initial main-chain cleavage.

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