New pyridinium salts as versatile compounds for dye sensitized photopolymerization Mohamad-Ali Tehfe a , Abbas Zein-Fakih a,b , Jacques Lalevée a,⇑ , Frédéric Dumur c , Didier Gigmes c , Bernadette Graff a , Fabrice Morlet-Savary a , Tayssir Hamieh b , Jean-Pierre Fouassier d a Institut de Science des Matériaux de Mulhouse IS2M – LRC CNRS 7228 – ENSCMu-UHA, 15, rue Jean Starcky, 68057 Mulhouse Cedex, France b Laboratoire de Matériaux, Catalyse, Environnement et Méthodes analytiques (MCEMA-CHAMSI), EDST, Université Libanaise, Campus Hariri, Hadath, Beyrouth, Lebanon c Aix-Marseille Université, CNRS, Institut de Chimie Radicalaire, UMR 7273, F-13397 Marseille, France d UHA-ENSCMu, 3 rue Alfred Werner, 68093 Mulhouse, France article info Article history: Received 27 July 2012 Received in revised form 2 October 2012 Accepted 11 October 2012 Available online xxxx Keywords: Dyes Pyridinium salt Radical photopolymerization Cationic photopolymerization Photoinitiators abstract A series of pyridinium salts were synthesized and investigated as new dyes for photoiniti- ating systems of polymerization. They exhibit a strong absorption at about 550 nm well matching with the visible light emission of different convenient visible light sources. Inter- estingly, very soft irradiation (halogen lamp) as well as laser diode exposure (457 and 532 nm) can be used. When employed in the presence of a silane and an iodonium salt, they efficiently initiate the free radical polymerization of acrylates and free radical pro- moted cationic polymerization of epoxides. An acrylate/epoxide blend is also easily poly- merized i.e. for the synthesis of interpenetrating polymer networks. In combination with amine, the proposed dyes can also initiate free radical polymerizations. The mechanisms analyzed by ESR and photolysis experiments are discussed for the different multi-compo- nent initiating systems. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction As very well known, visible light induced photopoly- merization reactions require the presence of a colored mol- ecule in the absorbing photoinitiating systems vPIS [1]. These vPISs can be designed for free radical polymerization FRP, cationic polymerization CP and free radical promoted cationic polymerization FRPCP. They schematically work according to (1)–(3), respectively. vPIS ! R Å ðhmÞ ð1Þ vPIS ! R þ ðhmÞ ð2Þ vPIS ! R Å ! R þ ðhmÞ ð3Þ Despite the fact that many systems are already known (see the most recent up-to-date review) [2], the design of novel vPIS remains an interesting research topic e.g. (i) to continuously improve the performance attained or (ii) to propose novel systems being able to meet new or promising possibilities of applications. In this context in the very last years, we have explored and developed new vPISs lying on several examples of dye structures such as ruthenium [3a] and iridium complexes [3b], violanthrone derivatives [3c], truxene [3d], diamine or azine [3e] based compounds, pyrromethenes [3e]. In the present paper, we will introduce a revival of interest for the use of pyridinium salts Py + in dye photosensitized polymerization reactions. Indeed, it has been already reported [4] that N-alkoxy pyridinium salts alkoxy-Py + cleave under UV light exposure (4a) and gener- ate (4b) an alkoxy radical and a pyridinium radical which further forms a pyridine and an acid through hydrogen abstraction. Cationic photopolymerization of cyclic ethers 0014-3057/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.eurpolymj.2012.10.010 ⇑ Corresponding author. E-mail address: j.lalevee@uha.fr (J. Lalevée). European Polymer Journal xxx (2012) xxx–xxx Contents lists available at SciVerse ScienceDirect European Polymer Journal journal homepage: www.elsevier.com/locate/europolj Please cite this article in press as: Tehfe M-A et al. New pyridinium salts as versatile compounds for dye sensitized photopolymerization. Eur Polym J (2012), http://dx.doi.org/10.1016/j.eurpolymj.2012.10.010