Two-dimensional time-domain H-1 NMR was used to investigate annealed isotactic polypropylene in the solid phase. The spin-lattice relaxation in the laboratory frame and in the rotating frame were correlated with the shape of the free induction decay to identify and characterize relaxation components over the temperature range -120 to 120 degrees C. Several phase transitions were observed, and three distinct solid phases, with different chain mobilities, were detected. Two of these phases were identified as regions with different mobilities within the crystalline phase. The third phase was characterized by a high degree of isotropy in molecular motion. This phase, identified as the amorphous phase, appeared as the polymer was heated above a low-temperature (-45 degrees C) phase transition. All transitions observed at higher temperatures occurred exclusively in this phase. About one-third of the polymer chains reside between crystalline lamellae, whereas the majority form amorphous regions outside fibrils of multilamellar structure. Furthermore, the glass-to-rubber transition, occurring above -15 degrees C, consists of three stages. During the first stage, between -15 degrees C and 15 degrees C, regions with an increased segment mobility (labeled intermediate phase) appear gradually within the amorphous phase. At 15 degrees C, the intermediate phase consists of similar to 10% of the polymer units, or one-third of the polymer units constituting the amorphous phase. Between 15 degrees C and 25 degrees C, the intermediate phase increases rapidly to 18%. This is associated with the appearance of semiliquid and Liquid regions, likely within the intermediate phase. Polymer chain segments (and possibly entire chains) involved in the liquidlike phases exhibit heterogeneous molecular motion with a correlation frequency higher than 10(6) Hz. These two stages of glass-to-rubber transition occur within amorphous regions outside multilamellar structures. The third stage of the glass transition, appearing above 70 degrees C, is associated with the upper glass transition and occurs within the interlamellar amorphous phase. Finally, on a timescale of 100 ms or less, spin diffusion does not couple the amorphous regions outside fibrils with crystalline and amorphous regions within multilamellar fibrils. However, on a timescale of hundreds of milliseconds to seconds, all different regions within isotactic polypropylene are partially coupled. It is proposed that the relative magnitude of the crystalline magnetization, as observed in the T-1 rho experiment, is a good measure of polymer crystallinity.