Free-radical crosslinking copolymerization of styrene and divinylbenzene: real time monitoring of the gel effect using fluorescence probe

The steady-state fluorescence and dilatometric techniques were used to stud y the free-radical crosslinking copolymerization of styrene (S) and commerc ial divinylbenzene (DVB) in bulk. Pyrene (Py) was used as a fluorescence pr obe for the in situ polymerization experiments. The time required for a sud den increase in the fluorescence intensity of Py was recorded for various D VB content and temperature. The monomer conversions and the gel points were recorded by dilatometry. To interpret the experimental data, a kinetic mod el was developed for the S-DVB copolymerization system. It was shown that b oth the pendant vinyl groups and Py molecules are affected by the reaction medium in a similar way, their mobility decreases as the DVB concentration increases or the temperature decreases. The reaction time at which the Py i ntensity in the fluorescence spectra exhibits a sudden increase corresponds to the reaction time at which the rate of polymerization becomes maximum r esulting from the gel effect. The results show that the fluorescence techni que can be used to follow the onset of the gel effect in S-DVB copolymeriza tion. (C) 1999 Elsevier Science Ltd. All rights reserved.