What affects the rate of free radical polymerization of a multifunctional acrylate photoinitiated by cyanine borate salts?

摘要

Cyanine dyes, widely used in color photography, can also be used as initiators of radical polymerization, initiated with visible light. The aim of this work was to check the possibility of application of borate salts of these dyes as photoinitiators of 2-ethyl-2-(hydroxymethyl)-1,3-propanediol triacrylate-TMPTA and to determine the effect of photininitator structure on the polymerization rate. 32 symmetric cyanine dyes-derivatives of benzothiazole and changing of heteroatom (S or O), substituent in the phenyl ring as well as the type of substituents in polymethine chain. Spectroscopic investigations of dyes used as well as their borate salts showed the intensive absorption band localized for thiocarbocyanine dyes in the range 550-600 nm while for carbocyanine dyes-in the range 480-510 nm. Replacement of halogen atom or ethylsulfate anion in the cyanine dye molecule to the following anions: n-, sec- or tert-butyltriphenylborate and tetra-n-butylborate gave the borate salts of cyanine dyes. 150 various borate salts of cyanine dyes have been used as photoinitiators of TMPTA photopolymerization. It has been stated that the ability of initiation of TMPTA [as 10 vol.% solution in 1-methyl-2-pyrrolidinone (MP)] polymerization depends on the type of heteroatom in the dye molecule, the type of substituent in the phenyl ring, the type of substituent in mezo position in polymethine chain and on borate anion structure. It has been also found that monomer conversion and quantum yield of the process depend also on the chemical structure of photoinitiator.