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The amplitudes of ring-and main-chain motions of a variety of polystyrenes have been established from the 13C NMR magic-angle spinning sideband patterns of dipolar and chemical shift tensors. The frequencies of the same motions have been determined by 7\(C) and Tlp(C) experiments. The most prevalent motion in these polymers is restricted phenyl rotation with a sizable average jump angle. Both the amplitude and frequency of this motion vary from one substituted polystyrene to another and from site to site within the same polystyrene. A small fraction of sites within some of the polystyrenes permits high-frequency (megahertz) ring flips in combination with main-chain rotational reorientation, also at high frequency. The concentration of these sites does not depend upon intrachain conformational or configurational defects but rather is determined by interchain glassy-state packing. Low-frequency (kilohertz) main-chain motion is insensitive to ring substitution for some of the polystyrenes, suggesting the presence of a cooperative motion in which the rings only translate as the main chain rotates.

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