DNP Signal Amplification as Sensitive Probe for Specific

Alarich-Weiss-Str. 8, D-64287 Darmstadt, Germany b Ernst-Berl Institute for Chemical Engineering and Macromolecular Science, Technische Universität...
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DNP Signal Amplification as Sensitive Probe for Specific Functionalization of Complex Paper Substrates Torsten Gutmann, Bharti Kumari, Li Zhao, Hergen Breitzke, Sebastian Schöttner, Christian Rüttiger, and Markus Gallei J. Phys. Chem. C, Just Accepted Manuscript • Publication Date (Web): 26 Jan 2017 Downloaded from http://pubs.acs.org on January 26, 2017

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The Journal of Physical Chemistry

DNP Signal Amplification as Sensitive Probe for Specific Functionalization of Complex Paper Substrates Torsten Gutmann,a* Bharti Kumari,a Li Zhao,a Hergen Breitzke,a Sebastian Schöttnerb, Christian Rüttigerb, Markus Galleib* a

Eduard-Zintl Institute for Inorganic and Physical Chemistry, Technische Universität Darmstadt, Alarich-Weiss-Str. 8, D-64287 Darmstadt, Germany b Ernst-Berl Institute for Chemical Engineering and Macromolecular Science, Technische Universität Darmstadt, Alarich-Weiss-Str. 4, D-64287 Darmstadt, Germany. Corresponding authors: [email protected], [email protected] Abstract In this work, it is shown how solid-state NMR combined with Dynamic Nuclear Polarization (DNP) can be employed as a powerful tool to selectively enhance the spectral intensity of functional groups on the surface of cellulose fibers in paper materials. As model system a poly(benzyl methacrylate) (PBEMA) functionalized paper material is chosen that contains hydrophobic and hydrophilic domains. The detailed analysis of the DNP NMR data and of T1ρ data suggests that inhomogeneous 1H-1H spin diffusion is responsible for the observed differences in signal enhancement. These findings are fundamental for the structural understanding of complex paper substrates for fluid transport or sensor materials. Introduction The structural characterization of functional paper materials is an essential step for gaining a deeper understanding of their physico-chemical properties. It is required for the rational design and optimization of their surface properties. In general, cellulose in combination with functional polymers is a potential platform for the preparation of so-called smart surfaces. The resulting materials are printable, flexible, light and thin. Paper sheets consist of non-woven lignocellulosic microfibers held together by H-bonds in the dry state. Due to the intrinsic properties of functional papers, such as thermal and chemical stability as well as adjustable morphology (e.g. porosity), their use in the advanced technological fields of printed electronics, capacitors, and sensors is of growing interest. 1-5 For this reason, functional papers provide a direct and technologically straight-forward control over the wettability and functionality through surface-attached polymers and they are desirable as platforms for microfluidics or sensing applications. 6-7 Functional paper substrates have exceedingly complex structures, which results in major challenges for characterization methods. Solid-state NMR in principle allows for the analysis of ill-defined complex materials since it enables the measurement of local interactions on surfaces. However, many paper materials contain surface areas of