Secondary transitions of aryl-aliphatic polyamides II. High-resolution solid-state 13C NMR investigation

• Published in: Polymer (Guilford) Vol. 41; no. 8; pp. 2989 - 2998
• Main Authors: Beaume, F., Lauprêtre, F., Monnerie, L.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01-04-2000; Elsevier
• Subjects: Applied sciences; Aryl-aliphatic copolyamides; Exact sciences and technology; High-resolution solid-state 13C NMR; Organic polymers; Physicochemistry of polymers; Properties and characterization; Secondary transitions; Thermal and thermodynamic properties; Secondary transitions; High-resolution solid-state 13C NMR; Aryl-aliphatic copolyamides; Solid state; Local mobility; Amide copolymer; Temperature effect; NMR spectrometry; Experimental study; Intramolecular mobility; Amide 12 copolymer
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/S0032-3861(99)00460-7

High-resolution solid-state
13C NMR experiments were performed on the two series of aryl-aliphatic copolyamides whose dielectric relaxation investigation is reported in the first paper of this series. The local motions were studied by following the temperature dependence of
13C chemical shift anisotropies and
13C–
1H dipolar couplings. In the copolyamides that contain a lactam-12 sequence, the lactam-12 sequences were shown to be involved in significant motions, even at low temperatures. In contrast, in the copolymers whose aliphatic part is a methylpentane sequence, the methylpentane sequences do not exhibit detectable motions at temperatures below 100°C. In all the systems investigated, the aromatic rings were shown to undergo oscillations whose amplitudes and axis depend of the relative
meta- or
para- positions of the substituents. In addition to these oscillations,
para-substituted rings are also involved in π-flips. The motions of the lactam-12 sequences were associated with the γ-relaxation processes whereas both oscillations and π-flips occur in the temperature and frequency ranges of the β-transition observed by dielectric relaxation.