Kinetic study of free‐radical polymerization photoinitiated by cyanine‐borate salts. II.

A series of cyanine butyltriphenylborate salts were prepared and tested as initiators of free‐radical polymerization photoinitiated via a photoinduced electron‐transfer process. For the majority of the tested series, the highest rate of photoinitiated free‐radical polymerization was observed when sec‐butyl radicals were formed. Essentially, there was no influence of the quantum yield of the free‐radical formation on the rate of the free‐radical polymerization initiated by the cyanine‐borate salts. The experimental data revealed that the relationship between the rate of polymerization and the free energy change for the electron transfer displayed typical Marcus region kinetic behavior. The photoreduction of the cyanine butyltriphenylborate salts produced colorless products. The efficiency of the bleached‐dye formation had no effect on the overall efficiency of photoinitiated polymerization. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2365–2374, 2000