meta-Terphenyls as versatile fluorescent molecular sensors for monitoring the progress of hybrid polymerization processes

Herein, the performance of a series of 2-amino-4,6-diphenylbenzene-1,3-dicarbonitrile derivatives in the role of fluorescent molecular sensors for monitoring progress of various photopolymerization processes by the Fluorescence Probe Technique (FPT) has been evaluated. It was found that all of the derivatives studied, except for the one containing a nitro substituent in its structure, showed high enough sensitivity and stability to be applied as versatile sensors for both cationic and free-radical polymerization processes. Next, the applicability of the sensors was applied for study of hybrid polymerization processes (i.e., both cationic and free radical polymerization reactions occurring simultaneously). The hybrid photopolymerization of pure glycidyl methacrylate (GlyMA) and the mixtures of GlyMA with 3,4-epoxycyclohexylmethyl 3,4-epoxy-cyclohexanecarboxylate (CADE), or CADE with trimethylolpropane triacrylate (TMPTA) was studied. It was found that during the hybrid photopolymerization of CADE/TMPTA mixtures, each monomer polymerized independently to form an interpenetrated polymer network (IPN). On the other hand, hybrid photopolymerization of GlyMA/CADE mixtures leads to a copolymer, where final functional group conversions are higher than those achievable by the corresponding photopolymerizations of pure GlyMA and CADE monomers. The use of m-terphenyl sensors allows for real-time monitoring of various hybrid polymerization processes and provides key information on the processes, which was not previously possible.