Photochemical Reactions in Polymeric Systems

Abstract

Photochemical reactions have been examined in relation with the physical properties of the solid polymeric matrix in which they are carried out. Three main reaction types are considered: (i) photocrosslinking reactions resulting from cyclodimerization of unsaturated groups and from the decomposition of photolabile groups into very reactive species, e.g. nitrenes from azides; (ii) photoisomerization reactions in the case of aromatic azoderivatives, and photochromic spirobenzopyran compounds; (iii) photodissociation reactions in the case of bisanthracene-and benzpinacol derivatives. Each class of reaction is illustrated by recent data from the literature, as well as by new results obtained in our laboratory in photochemical isomerization and dissociation experiments. The reversibility of these reactions is discussed in terms of chain segment mobility and free volume distribution, and correlated diffusion effects in the case of dissociation reactions. The importance of the chemical incorporation of the photosensitive groups into the polymer is stressed by comparison with the photoresponse of corresponding model compounds dissolved in a polymeric matrix. © 1975, Walter de Gruyter. All rights reserved.