Real-time kinetic study of the polymerization activity of the photoinitiator system p-nitroaniline/N,N-dimethylaniline by real time IR spectroscopy

The polymerization process of different acrylic monomers photoinduced by th e bimolecular system p-nitroaniline/N,N-dimethylaniline (pNA/DMA) under UV radiation was analyzed in situ by real-time IR spectroscopy. To this purpos e an inexpensive, automatized and simple apparatus based on commercially av ailable items easily assembled was developed. The conversion versus time cu rves recorded allow the polymerization rate and quantum yield to be determi ned at any stage of the reaction. The effect of various factors such as inc ident light-intensity, initiator and coinitiator concentration, functionali ty of the monomer on the kinetic of the polymerization process was analyzed . This technique allowed the evaluation of the dark polymerization develope d just after a dose of UV radiation by being able to measure and control th e polymerization degree. A comparison with alternative methods as Photo-DSC technique allows to evaluate the effect of the sample thickness on the kin etics of a photoinitiated acrylate polymerization.