Variable temperature and variable stress nuclear magnetic resonance spectroscopic and imaging studies are reported for a commercial sample of high impact polystyrene. Liquid nuclear magnetic resonance microscopy and solid state stray field imaging studies indicated that imposed stress affects the molecular chain dynamics only of the polybutadiene region and not of the polystyrene (PS) matrix. The molecular chain dynamics of the components of the composite were further studied by variable temperature relaxation time and chemical shift anisotropy (CSA) measurements. The variable temperature (30 o C - 210 o C)1H spin-lattice relaxation time in the rotating frame (T1pH) studies showed that up to 160 o C the PS undergoes at least 2 different modes of motion, while at 95 o C a change from asymmetric to axially symmetric in the CSA pattern of the aromatic ring 13C-{1H} resonances revealed that the conformations of the phenyl rings are effectively locked below that temperature.