THERMALLY CROSS-LINKED RIGID-ROD ARAMIDS .1. SYNTHESIS OF A NEW MONOMER AND ITS POLYMERIZATION

With 3,5,7-tetrahydro-2,6-dithia-s-indacene-4,8-diamine (DSDA) (8), a new monomer for the synthesis of thermally crosslinkable rigid-rod ara mids was developed. DSDA was copolymerized with p-phenylenediamine and terephthaloyl dichloride by a low-temperature solution Polycondensati on to give high-molecular-weight aramids (inherent viscosity eta(inh) > 2,2 dL/g). The fraction of DSDA could be varied from 0 to 100 mol-% of the diamine used in the condensation. All polymers showed a weight loss due to thermal elimination of SO2. Thermal crosslinking could be effected by curing the samples at high temperatures (280-320-degrees-C ). The crosslinking reaction was investigated by means of thermogravim etry (TG), thermogravimetry/mass spectrometry (TG-MS), Fourier transfo rm infrared (FT-IR), C-13 Cross polarization-magic angle spinning nucl ear magnetic resonance (C-13 CP-MAS NMR) and electron paramagnetic res onance (EPR). The activation energy for this reaction was found to be between 150 and 170 kJ/mol. Curing of the polymer samples led to the g eneration of stable, matrix-isolated radicals.