13C and 1H n.m.r. studies of solid polyolefines

Cudby, M.E.A.; Harris, Robin K.; Metcalfe, Kenneth; Packer, Kenneth J.; Smith, P. W.; Bunn, Alan

doi:10.1016/0032-3861(85)90026-6

Cited by 30 publications

(5 citation statements)

References 16 publications

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“…13 C CP-MAS spectra were recorded under high-power decoupling from protons, using a recycle delay of 3 s, a contact time of 2 ms, a MAS frequency of 3.5 kHz and accumulating 600 transients. The same conditions were used to record 13 C Delayed CP-MAS 16 spectra, for which a delay of 100 μs was inserted between the 90°1H pulse and the CP irradiation, in order to let the magnetization of protons with short T 2 to completely decay. Scheme 1.…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

Insights into Shape-Memory Poly(ε-caprolactone) Materials by Solid-State NMR

et al. 2014

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Polymeric materials showing shape-memory behavior are attracting large interest especially in the field of biomaterials. Despite the large number of studies aimed at charaterizing macroscopic features, detailed investigations of properties at the nanometric scale and molecular level are still very few. In this work we present a multinuclear and multitechnique solid-state NMR investigation on recently developed hybrid materials formed by sol− gel cross-linked alkoxysilane terminated poly(ε-caprolactone), showing very interesting shape-memory behavior. By investigating several spectral and relaxation properties of 29 Si, 13 C, and 1 H nuclei present in the hybrid material, we could characterize and compare the structural, dynamic, and phase properties of a sample fixed in a stretched temporary shape with those of a sample in the permanent shape. Interesting differences could be observed: in particular, the sample fixed in the temporary shape showed a larger amount (40% instead of 35%) of crystalline phase and amorphous domains in which polymeric chains experienced a more restricted molecular mobility, as inferred from proton T 2 values. Moreover, from 13 C spectra recorded by varying the orientation of the sample with respect to the direction of the magnetic field, it was possible to clearly detect that about 90% of PCL chains, mainly in the crystalline domains, but also in the amorphous ones, were strongly aligned along the stretching direction. If subjected to heating, so to remove the temporary shape, the sample showed a melting temperature a few degrees higher, a sligthly more rigid melt phase, and a complete loss of molecular alignment.

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Section: ■ Experimental Sectionmentioning

confidence: 99%

Insights into Shape-Memory Poly(ε-caprolactone) Materials by Solid-State NMR

et al. 2014

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“…Solid-state high-resolution 13C NMR spectroscopy is a powerful technique for characterizing the crystalline and noncrystalline regions of semicrystalline polymers. [1][2][3][4][5][6][7][8][9][10][11][12][13] Recently we found on the basis of the measurements of 13C spin-lattice and spin-spin relaxation times and computer line-shape analyses for the total dipolar decoupling/ magic angle spinning (DD/MAS) spectra that polyethylene samples crystallized from the melt were composed of not only crystalline and amorphous phases but also crystalline-amorphous interphase.1 The thickness of the interphase was estimated to be about 30 Á, which corresponds well to the theoretical value calculated using a lattice model by Flory et al 14 Isotactic polypropylene, which is also a highly crystalline polymer, has already been studied by several groups using solid-state high-resolution 13C NMR spectroscopy. Bunn et al11 measured CP/MAS spectra of annealed and quenched -form (monoclinic) and /3-form (hexagonal) samples at room temperature.…”

Section: Introductionmentioning

confidence: 99%

High-resolution solid-state carbon-13 NMR study of isotactic polypropylenes isothermally crystallized from the melt

Saito¹,

Moteki²,

Nakagawa³

et al. 1990

Macromolecules

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The phase structure of isotactic polypropylenes isothermally crystallized from the melt has been examined at different temperatures by solid-state high-resolution 13C NMR spectroscopy using VT/MAS (variable temperature/magic angle spinning). On the basis of 13C spin-lattice relaxation and computer line-shape analyses, it has been found that polypropylene samples are composed of not only crystalline and amorphous components but also another noncrystalline component with 31-helical conformation. Similar NMR analyses at different temperatures have revealed that a reversible structural change between the 31-helical and random conformations occurs in the noncrystalline region at 60-110 "C.

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“…Experimental [14]. Proton spin-lattice in the laboratory (T 1 ) and in the rotating (T 1r ) frame relaxation times were measured using the inversion recovery-CP/MAS [15] and the variable spin-lock time-CP/MAS [16] sequences, respectively.…”

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confidence: 99%