STRUCTURE-PROPERTY RELATIONS IN POLYMERIZATION PHOTOINITIATORS .2. PHENYLACETOPHENONE DERIVATIVES

Nine substituted hydroxyalkylphenylketones have been investigated through time resolved laser spectroscopy. The behaviour of some of these ketones bearing an ether substituent at the para position of the phenyl ring is special: their triplet states are short-lived (8.5-15 nsec in dearated solutions) but are longer-lived than the parent unsubstituted compound (1.4 nsec). Introduction of thio and dialkyl amino groups leads to an increase of the lifetimes (3-4-mu-sec). These substituents change the reactivity of the triplet states in the presence of oxygen, monomer and amine but have a weak influence on the rate of polymerization of MMA in organic solvent initiated by light irradiation of these compounds. All the excited state processes are discussed.