Following in situ photoinitiated polymerization of multifunctional acrylic monomers by fluorescence and photocalorimetry simultaneously

The photoinitiated polymerization of multifunctional (meth)acrylic monomers was simultaneously monitored in real time by fluorescence and differential scanning calorimetry. As the curing proceeds, the fluorescence emission changes due to an increase in the viscosity of the microenvironment. A good correlation between fluorescence intensity and degree of conversion was established by using two different fluorescent probes, each having the same fluorophore, dialkylamino derivatives of 7-nitro-2-oxa-1,3-diazol. One of the probes contains an acrylic moiety which can react with the monomers labelling the formed network. The use of the first moment of fluorescence is presented as a suitable methodology to avoid experimental fluctuations. Furthermore, the influence of the length of the spacer between the acrylic groups in the polymerization reaction kinetics and fluorescence changes has been also discussed in terms of reaction diffusion controlled termination kinetics and free volume fraction. It was concluded that the fluorescence method is a powerful tool to study the kinetics of photopolymerization of multifunctional monomers.The authors would like to thank the Union European Commission for funding through the BRITE-Euram Project (BE97-4472). Gratitude is also extended to Plan Nacional I+D+I (Ministerio de Ciencia y Tecnologı́a) for financial support (MAT1998-0518-CE and MAT2000-1671). We thank to Dr K. Dietliker, from Ciba Speciality Chemicals, for providing the photoinitiators. The authors are grateful to Valentı́n Guadaño from Lasing for helpful discussions regarding to the optical coupling between the calorimeter and spectrofluorimeter. J. Baselga wishes to thank CAM (PRICIT Programme)