- K. Schäler, R. Bärenwald, A. Achilles, C. Hackel, K. Saalwächter.
Robust NMR Approaches for the Dynamics in Crystallites of Poly(?-caprolactone) As Investigated
by Solid-State NMR.
Macromolecules 46, 7818-7825(2013).
We investigate the molecular dynamics within the crystallites of poly(ε-
caprolactone), PCL, crystallized from the melt by means of high-field 13C and low-field 1H
NMR spectroscopy, addressing the question of whether it can be classified as a “crystal-fixed”
polymer without chain motion through the crystallites. We address fast, slow, and intermediateregime
(microseconds to milliseconds time scale) motions by means of high-resolution of
13C DIPSHIFT and CODEX MAS experiments as well as low-resolution static 1H FID and
MSE measurements over a range of temperatures. The DIPSHIFT data provide information
on motionally averaged 13C-1H dipole-dipole couplings and indicate the presence of fast
(≤ 1 μs) methylene group librational motions within the crystalline phase, where the
amplitudes increase with increasing distance from the rather rigid ester groups. The CODEX
experiments, addressing slow (≥ ms) local rotations of the chemical-shift anisotropy tensors, suggest the absence of slow
intracrystallite chain dynamics. 1H second-moment and MSE signal loss data of the crystalline fraction, along with the DIPSHIFT
and CODEX data, indicate that intermediate-regime chain motions do not take place in PCL crystallites.of ultraslow large-angle two-site jumps accompanied by small-angle fluctuations that occur 10 times more quickly.