DOUBLE-MODULATION AND CONVENTIONAL ELECTRON-SPIN-RESONANCE SPECTRA OF SPIN-LABELED CROSS-LINKED POLYSTYRENE

The recently introduced method of detecting homogeneous linewidths from inhomogeneously broadened ESR spectra using the double-modulation technique has been applied in parallel with the conventional method to study molecular motion in crosslinked polystyrene. The rotational correlation time in the slow-motion region determined from the homogeneously broadened line varied from 1. 68 multiplied by 10** minus **5 to 8. 0 multiplied by 10** minus **6 s between 150 and 340 K. Double-modulation spectra appear to be very sensitive to local motion at low solvent concentration. The influences of crosslink density and solvent concentration on both local and overall motion is analyzed.