Domain sizes in heterogeneous polymers by spin diffusion using single-quantum and double-quantum dipolar filters.
1H spin-diffusion experiments employing a double-quantum (DQ) dipolar filter were performed for the characterization of the microdomain structure of heterogeneous samples. For this purpose the NMR spin-diffusion process was analysed based on a model morphology of three different domains with arbitrary sizes, diffusivities, and filter efficiency. General analytical solutions for z magnetization source and sink were obtained valid for a one-dimensional lamellar morphology in the full range of spin-diffusion times. These solutions of the spin-diffusion equations were used for determining the crystalline, interface, and amorphous domain sizes in polystyrene-poly(ethylene oxide) (PS-PEO) and poly(hydroxyethylmethacrylate)-poly(ethylene oxide) (PHEMA-PEO). The DQ dipolar filter has a good efficiency for PS-PEO but is only partially efficient in filtering the signal of the mobile domains in the PHEMA-PEO diblock copolymer. The domain sizes measured by the DQ filter method are compared to those obtained using the traditional dipolar filter creating z magnetization in the mobile domains.
Buda
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A
Institut für Technische Chemie und Makromolekulare Chemie, Rheinisch-Westfälische Technische Hochschule, Worringerweg 1, D-52056 Aachen, Germany.
Demco
D E
DE
Bertmer
M
M
Blümich
B
B
Reining
B
B
Keul
H
H
Höcker
H
H