Fluorescence polarization study of the curing process of epoxide with aminimide

The curing process of epoxide (Epikote 828, EK) with aminimide (trimethylamine valerimide, TMAV) was studied by a fluorescence polarization method. Two types of probe molecules were used: One was perylene (PE), which was just physically incorporated into the curing mixture and termed as the “extrinsic” probe, and the other was fluorescent product(s) formed during curing of EK with TMAV, which was termed as the “intrinsic” probe. Extraction experiments revealed that the “intrinsic” probe was covalently incorporated into the crosslinked matrix. No emission was observed for the “intrinsic” probe before heating, but its intensity increased with curing at 150°C. Fluorescence anisotropy (r) of both EK/TMAV/PE and EK/TMAV systems increased monotonically with curing time at the initial stage and then remained nearly constant. This means that at the early stage of curing the network becomes rigid enough to restrict rotational diffusion of the probe molecules. Calculated r values for the “extrinsic” probe alone were lower than observed r values of the “intrinsic” probe, which was well explained in terms of the mode of incorporation of the two types of the probe molecules into the matrix.