Molecular motions of single polycarbonate (PC) chains threaded into crystalline gamma-cyclodextrin (gamma-CD) channels were examined using solid-state C-13 NMR and molecular dynamics simulations. The location of PC within the channels was confirmed by spin diffusion from a PC C-13 label to natural-abundance C-13 of the gamma-CD. Rotor-encoded longitudinal magnetization (RELM) (under 7-kHz magic-angle sample-spinning conditions) was combined with multiple-pulse H-1-H-1 dipolar decoupling to detect large-amplitude phenyl-ring motion in both bulk PC and polycarbonate gamma-cyclodextrin inclusion compound (PC-gamma-CD). The RELM results indicate that the phenyl rings in PC-gamma-CD undergo 180 degrees flips faster than 10 kHz just as in bulk PC. The molecular dynamics simulations show that the frequency of the phenyl-ring flips depends on the cooperative motions of PC atoms and neighboring atoms of the gamma-CD channel. The distribution of protonated aromatic-carbon laboratory and rotating-frame C-13 spin-lattice relaxation rates for bulk PC and PC-gamma-CD are similar but not identical. The distributions for both systems arise from site heterogeneities. For bulk PC, the,heterogeneity is attributed to variations in local chain packing, and for PC-gamma-CD the heterogeneity arises from variations in the location of the PC phenyl rings in the gamma-CD channel. (c) 2007 Wiley Periodicals, Inc.