Basic principles of static proton low-resolution spin diffusion NMR in nanophase-separated materials with mobility contrast |
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| Affiliation: | 1. Radboud University, Institute for Molecules and Materials (IMM), Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands;2. Dutch Polymer Institute (DPI), P.O. Box 902, 5600 AX Eindhoven, The Netherlands;3. Department of Mechanical Engineering, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands;4. Borealis Polyolefine GmbH, Sankt-Peter-Strasse 25, 4021 Linz, Austria;5. DSM Resolve, P.O. Box 18, 6160 MD Geleen, The Netherlands;6. DSM Ahead, P.O. Box 18, 6160 MD Geleen, The Netherlands;1. Instituto de Física de São Carlos, Universidade de São Paulo, P.O. Box 369, São Carlos, 13560-970 SP, Brazil;2. School of Chemical and Physical Sciences, Victoria University of Wellington, PO Box 600, Wellington, New Zealand;1. Laboratory of Pharmaceutical Technology, Faculty of Pharmacy and Pharmaceutical Science, University of Toyama, 2630 Sugitani, Toyama-shi, Toyama 930-0194, Japan;2. Nichi-Iko Pharmaceutical Co., Ltd., Formulation Development Department, 205-1 Shimoumezawa, Namerikawa-shi, Toyama 936-0857, Japan;1. Fraunhofer Institute for Manufacturing Technology and Advanced Materials IFAM, Wiener Str. 12, D-28359, Bremen, Germany;2. University of Bremen, Chemical Department, Leobener Str., D-28359, Bremen, Germany;3. Martin-Luther Universität Halle-Wittenberg, Institut für Physik - NMR, Betty-Heimann-Str. 7, D-06120, Halle (Saale), Germany;1. State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Renmin Street 5625, 130022, Changchun, PR China;2. School of Applied Chemistry and Engineering, University of Science and Technology of China, Hefei, 230026, PR China;3. Westfälische Wilhelms-Universität, Institut für Physikalische Chemie, Corrensstraße 28/30, 48149, Münster, Germany;4. V.Lit.Consult, Gozewijnstraat 4, 6191, WV Beek, the Netherlands |
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| Abstract: | We review basic principles of low-resolution proton NMR spin diffusion experiments, relying on mobility differences in nm-sized phases of inhomogeneous organic materials such as block-co- or semicrystalline polymers. They are of use for estimates of domain sizes and insights into nanometric dynamic inhomogeneities. Experimental procedures and limitations of mobility-based signal decomposition/filtering prior to spin diffusion are addressed on the example of as yet unpublished data on semicrystalline poly(ϵ-caprolactone), PCL. Specifically, we discuss technical aspects of the quantitative, dead-time free detection of rigid-domain signals by aid of the magic-sandwich echo (MSE), and magic-and-polarization-echo (MAPE) and double-quantum (DQ) magnetization filters to select rigid and mobile components, respectively. Such filters are of general use in reliable fitting approaches for phase composition determinations. Spin diffusion studies at low field using benchtop instruments are challenged by rather short 1H T1 relaxation times, which calls for simulation-based analyses. Applying these, in combination with domain sizes as determined by small-angle X-ray scattering, we have determined spin diffusion coefficients D for PCL (0.34, 0.19 and 0.032 nm2/ms for crystalline, interphase and amorphous parts, respectively). We further address thermal-history effects related to secondary crystallization. Finally, the state of knowledge concerning the connection between D values determined locally at the atomic level, using 13C detection and CP- or REDOR-based “1H hole burning” procedures, and those obtained by calibration experiments, is summarized. Specifically, the non-trivial dependence of D on the magic-angle spinning (MAS) frequency, with a minimum under static and a local maximum under moderate-MAS conditions, is highlighted. |
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| Keywords: | Low-field NMR Semicrystalline polymers Polymer crystallization Polymer dynamics Nanophase separation Block copolymers |
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