Local chain dynamics in poly(fluorocarbonate)s

Magic-angle spinning C-13{1H} and C-13-{F-19} recoupling NMR experiments ha ve been performed on two polycarbonates with fluoro substituents on every f ourth ring in the main chain. The results of these experiments show that th e fluoro-substituted rings do not undergo 180 degrees ring flips faster tha n 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(flu orocarbonate) glasses as revealed by shifts and broadening of the dynamic m echanical gamma transitions.