Magic-angle spinning C-13{1H} and C-13-{F-19} recoupling NMR experiments have been performed on two polycarbonates with fluoro substituents on every fourth ring in the main chain. The results of these experiments show that the fluoro-substituted rings do not undergo 180 degrees ring flips faster than 10 kHz at 300 K. Most if not all of the unsubstituted rings are flipping. The fluoro substitutions also affect global chain dynamics in the poly(fluorocarbonate) glasses as revealed by shifts and broadening of the dynamic mechanical gamma transitions.