Dynamics in the crystalline polymorphic forms I and II and form III of isotactic poly-1-butene

Following an earlier study of the H-1 relaxation and NMR line shapes, we ha ve carried out, selective one-dimensional and two-dimensional C-13 solid-st ate NMR studies that yield to detailed interpretation of the dynamics in fo rm I, II, and III polymorphs of isotactic poly-l-butene. A specific defect diffusion along the side group is proposed to account for the temperature d ependence of the C-13 spectra in form I. The backbone of the helix in forms II and III is shown to undergo large angle motions above the glass-transit ion temperature. High-resolution solid-state C-13 two-dimensional exchange NMR under magic-angle spinning with cross-polarization techniques demonstra tes the existence of slow rotational jumps of the helices in form III with typical jump rates of about; 10 s(-1). (C) 2000 John Wiley & Sons, Inc.