A fast, efficient, inexpensive and green way to outdoor photopolymerization

M. PAULA MILITELLO; GABRIELA V, PORCAL; SONIA G. BERTOLOTTI; CARLOS M. PREVITALI; ERNESTO M. ARBELOA

SOLAR ENERGY

PERGAMON-ELSEVIER SCIENCE LTD

Año: 2023 vol. 258 p. 270 - 277

0038-092X

A series of environmentally friendly photoinitiating systems operating under mild conditions of visible light (Vis-PIs) were tested for vinyl polymerization using sunlight as a free of charge radiation source. These Vis-PIs basedon water soluble xanthene dyes showed good performances after deaerating with an inert gas, obtaining colorlesspolymers with gravimetric yields up to 80–90% after short irradiation times (2–15 min). Aqueous solutions of thematerials were highly viscous and viscosimetric measurements yielded molecular weights up to 106. Surprisingly,the evaluated Vis-PIs also worked successfully under ambient air atmosphere, obtaining similar polymeryields in the same irradiation times. Photolysis experiments and transient spectroscopy were used to shed lighton the mechanism of the process, allowing both triplets and radicals formation of the dyes to be identified even inthe presence of air. The kinetics of photopolymerization was studied following the monomer conversion atseveral irradiation times by FTIR. The results were interpreted based on kinetic data collected as competitivequenching mechanisms between the co-initiator and oxygen for the excited dyes. The present report represents abreakthrough in the search for fast, efficient and inexpensive Vis-PIs with low ecological impact, which can bevery useful in outdoor coating applications among others.