N-substituted 1,8-naphtalene imide-based (macro)initiator for investigation of photochemically induced ATRP process

Abstract

The exact mechanism of photochemically induced atom transfer radical polymerization (photoATRP) performed without venting the reaction mixture, remains not fully elucidated, especially the effect of oxygen on initiation efficiency. Here new photoactive 1,8-naphtalene imide-based compound was synthesized and applied as an initiator in copper-catalyzed photoATRP. The naphthalene-based photoactive compound was designed to serve as fluorescent markers at the beginning of the polymer chain for the study of the initiation efficiency of photoATRP with minimal effect on the polymerization mechanism itself. Photoactive naphthalene-1,8-dicarboxylic acid derivative (NI) bearing alkyl bromide initiator was synthesized in a two steps process starting from commercially available naphthalic anhydride and subsequently utilizing carboxylic acid derivatives for esterification. After successfully preparing the potential initiator, it was applied for the first time in photoATRP of acrylates in various solvents (DMF, DMSO) in the presence of air. Two catalytic systems in ppm amounts were used comprising either CuBr₂/ tris[2-(dimethylamino)ethyl]amine (Me₆TREN) or CuBr₂/ tris(2-pyridylmethyl)amine (TPMA) complex. The systematic study of the effect of solvent and catalytic complex allowed optimization of conditions to achieve high control over the molar masses and narrow dispersity while minimizing the negative effect of naphthalene imide chromophore. The gel permeation chromatography (GPC) equipped with a fluorescent detector was used for investigation of the initiation efficiency during photoATRP from low molecular weight naphthalene imide-based initiator as well as during chain extension photoATRP. As a potential applicability of the fluorescently labeled polyacrylates, they were used as ink for security printing.