PHOTODEGRADABILITY OF STYRENE COPOLYMERS CONTAINING ALPHA-PHENYL AND BETA-PHENYLKETONE AS CHAIN UNITS - POLYKETONES SYNTHESIZED BY HYDROLYSIS OF THE POLYMERS AND COPOLYMERS OF ACETOXYPHENYLBUTADIENE AND PHENYL(TRIMETHYLSILOXY)BUTADIENES

The present work reports on the photodegradation of macromolecules (po ly(styrene-co-carbon oxide) having alpha-phenyl and beta-phenylcarbony l groups along the main chain, The photochemical behaviour of polyketo nes containing beta-phenylcarbonyl groups and their comparison with th e behaviour of a polyketone containing alpha-phenylcarbonyl are expect ed to give useful informations. With this purpose polyketones constitu ted of 3-oxo-1-phenylbutane-1,4-diyl units (i) regularly head-to-tail linked (I), (ii) included in polystyrene (II) or (iii) in poly(1-pheny lbutadiene) (III) and polyketone constituted of 3-oxo-2-phenylbutane-1 ,4-diyl units (IV) have been considered. The, synthesis of I by hydrol ysis of polymers of 3-acetoxy-1-phenyl-1,3-butadiene (2a) and of 1-phe nyl-3-(trimethylsiloxy)-1,3-butadiene(2b) have been tested: the polyke tones I, are proved to be more easily accessible from 2 b and its poly mer (3 b) than from 2 a and its polymer (3 a). The polyketones II, III and IV have then been synthesized from the copolymer (4) of 2 b with styrene, the copolymer (5) of 2b with 1-phenyl-1,3-butadiene, and the polymer (8) of 2-phenyl-3-(trimethylsiloxy)-1,3-butadiene (7), respect ively. The photochemical behaviour of these polyketones and copolyketo nes is in accordance with the previously observed regiospecific alpha- phenyl-side towards the beta-phenyl-side fragmentation and shows that the expected photosensibilisation of the beta-phenyl-side fragmentatio n by increasing phenyl to carbonyl ratio is not observed.