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

Abstract

Following an earlier study of the 1H relaxation and NMR line shapes, we have carried out selective one‐dimensional and two‐dimensional 13C solid‐state NMR studies that yield to detailed interpretation of the dynamics in form I, II, and III polymorphs of isotactic poly‐1‐butene. A specific defect diffusion along the side group is proposed to account for the temperature dependence of the 13C spectra in form I. The backbone of the helix in forms II and III is shown to undergo large angle motions above the glass‐transition temperature. High‐resolution solid‐state 13C two‐dimensional exchange NMR under magic‐angle spinning with cross‐polarization techniques demonstrates the existence of slow rotational jumps of the helices in form III with typical jump rates of about 10 s−1. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2611–2624, 2000

Solid-State Nuclear Magnetic Resonance

“…Studies of cold-drawn high-density polyethylene showed that the "intermediate" component is a primarily all-trans configuration that has higher disorder than the crystalline component (100). Similar studies of the dynamics of isotactic poly(1-butene) have been reported (101). The dynamics of nylon-6 fibers spun at several speeds were examined with NMR, and the NMR properties were shown to change with the spinning rate (102).…”

Chain Dynamics, Conformations, and Phase Transformations for Form III Polymorph of Isotactic Poly(1-butene) Investigated by High-Resolution Solid-State13C NMR Spectroscopy and Molecular Mechanics Calculations

“…The observed doublet signals are attributed to the existence of noncongruent two sites, sites A and B, for the constitutional repeating units in form III as illustrated in Figure 2. 14,18 The merge of the split signals above 272 K results from the rapid dynamical exchange between sites A and B within the polymer chains. This exchange is brought about by the 90°helical jump motion of the polymer chains around their helical axes in the crystal lattice.…”

“…In the present work, we use the minimum value (Tg ) 248 K) for i-PB in the literature. [18][19][20] The mixed sample of forms III and I′, heat-treated form III, was prepared by heating the form III-rich sample in an oil bath at 368 K for 1 h. The amorphous sample was obtained by quenching the virgin sample into a liquid nitrogen bath after keeping it in an oil bath at 413 K (above T m of form I) for 5 min. Special attention was paid for the amorphous sample, because the amorphous chains immediately crystallize into form II even at room temperature due to its low Tg.…”

“…Belfiore et al 17 showed that the 13 C chemical shifts of the main-chain signals of i-PB depend on the dihedral angles in the main chain of each form. Maring et al 18 investigated the side-chain conformation in form I in the wide temperature range. They insisted that the side-chain conformation in form I adopts the t-g′, g-t, and g′-g conformations below T g ) 248-253 K 19 and that a rapid exchange among them occurs above T g .…”

“…Some other solid-state NMR methods were also applied to elucidate the chain dynamics in various forms of i-PB. [18][19][20] Maring et al suggested using the 1 H broad-line and relaxation measurements 19 that the polymer chains in forms I and I′ are rigid well above T g , while those in forms II and III are mobile. 13 C 2D exchange NMR spectroscopy was applied to the investigation of the molecular motions in i-PB.…”