1H nuclear magnetic resonance studies of domain structures in polymers

Abstract

The structures of amorphous (noncrystalline) domains in polyethylene, conditioned (at 150 °C for 15 min) and unconditioned polypropylene films and a vitrain portion of Kentucky No. 6 coal have been investigated using the Goldman-Shen NMR pulse sequence which monitors the transfer of 1H magnetization from the amorphous to the crystalline domains. The diffusion equation is solved with respect to such transfer. The size and shape of the amorphous domain is inferred by fitting the theoretical results to the experimental data. It seems that the layer-like configuration is a poor description for the polyethylene and polypropylene films unless the spatial orientation of the amorphous domain is isotropic. However the spherical configuration is inadequate for Kentucky No. 6 vitrain. The average width b̄ of the amorphous domain is 90–150 Å for polyethylene, 20–30 Å for uncontinued polypropylene film, and 30–50 Å for the conditioned films. The diffusion of magnetization in the amorphous domain of Kentucky No. 6 is faster than that of the polymers, though the dipolar interaction is much weaker in the former. A transfer process due to tranlational motion of small mobile chemical species is suggested.

Solid state 1H NMR study of molecular dynamics and domain sizes in PBT with the fullerene derivates: Decylamine–C60 and tetracyanoethylene oxide–C60

“…The study of the structure of domains in polymeric solids is extremely important for the understanding of the mechanical properties of polymers [4]. Inside amorphous domains, the polymer chains may undergo low-frequency libration motions [5] in the range of 10-100 kHz and can dissipate energy as heat to the surroundings, which is a mechanism of relieving tension when the mechanical stress is applied to a polymer [4]. Solid-state 1 H NMR techniques correlate structure and molecular mobility information with the heterogeneous domains and phases [6].…”

“…These polymers are characterized by the existence of a mobile amorphous component and a rigid crystalline one. The study of the structure of domains in polymeric solids is extremely important for the understanding of the mechanical properties of polymers [4]. Inside amorphous domains, the polymer chains may undergo low-frequency libration motions [5] in the range of 10-100 kHz and can dissipate energy as heat to the surroundings, which is a mechanism of relieving tension when the mechanical stress is applied to a polymer [4].…”

Solid-State 13C Nuclear Magnetic Resonance Characterization of Cellulose in the Cell Walls of Arabidopsis thaliana Leaves

“…This is very similar to a value of T,(H) = 8. (Cheung and Gerstein, 1981), but sufficiently long for the material to be labeled "mobile" or "semirigid" rather than "rigid crystalline. "…”

Nmr studies on the presence of domain structures in polysaccharides

“…While spin diffusion is viewed as an impediment with the loss of magnetic shielding information, it is also a virtue that can reveal morphological details through Goldman-Shen-type 24 In 'H dipolar coupled systems, discrimination of spatial inhomogeneities by 'H-nmr can be achieved only for a certain range of length scales.29 Spatial fluctuations within the correlation length of the local dipolar fields cannot be resolved. This sets a lower bound of resolution to a few near-neighbor distances, i.e., about 5 I r 2 = 11 8, in the present studies.…”