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A combination of DSC, SAXS, WAXD, 1H time-domain, and frequency domain NMR measurements was used for determining the amount of rigid/crystallinity, semirigid, and soft fractions of iPP. Changes in the rigid, semirigid, and soft fractions of isotactic polypropylene (iPP) were investigated as a function of temperature, annealing time, and annealing temperature. The most probable iPP morphology was established by TEM and by comparing 1H spin-diffusion data with data from multidimensional solutions of the spin-diffusion equations. Proton NMR spin-diffusion method, which employs double-quantum (DQ) and Goldman−Shen dipolar filters, was used in order to provide the domain thickness in iPP. The temperature dependence of spin diffusivities was taken into account, and a semiquantitative theory is presented for this dependence in the case of amorphous domains. A combination of 1H spin-diffusion NMR and SAXS was used to estimate the lamellar thicknesses for nonannealed and annealed iPP samples. Annealing at temperatures above 110 °C causes increases in the lamellar thickness and the crystallinity and a decrease in the chain mobility of rigid and semirigid fractions. The above quantities and the chain dynamics are reported for three annealing temperatures, 134, 143, and 153 °C, and an annealing time in the range of 15 min to 30 h. It is shown that the crystalline domains thickening during annealing of iPP can be described by a model based on irreversible thermodynamics. A phenomenological correlation is established between 1H transverse magnetization relaxation rate of the rigid fraction of iPP and the annealing temperatures.

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