title: Cross-Linking Cellulosic Fibers with Photoreactive Polymers: Visualization with Confocal Raman and Fluorescence Microscopy.
abstract: The properties of paper sheets can be tuned by adjusting the surface or bulk chemistry using functional polymers that are applied during (online) or after (offline) papermaking processes. In particular, polymers are widely used to enhance the mechanical strength of the wet state of paper sheets. However, the mechanical strength depends not only on the chemical nature of the polymeric additives but also on the distribution of the polymer on and in the lignocellulosic paper. Here, we analyze the photochemical attachment and distribution of hydrophilic polydimethylacrylamide-co-methacrylate-benzophenone P(DMAA-co-MABP) copolymers with defined amounts of photoreactive benzophenone moieties in model paper sheets. Raman microscopy was used for the unambiguous identification of P(DMAA-co-MABP) and cellulose specific bands and thus the copolymer distribution within the cellulose matrix. Two-dimensional Raman spectral maps at the intersections of overlapping cellulose fibers document that the macromolecules only partially surround the cellulose fibers, favor to attach to the fiber surface, and connect the cellulose fibers at crossings. Moreover, the copolymer appears to accumulate preferentially in holes, vacancies, and dips on the cellulose fiber surface. Correlative brightfield, Raman, and confocal laser scanning microscopy finally reveal a reticular three-dimensional distribution of the polymer and show that the polymer is predominately deposited in regions of high capillarity (i.e., in proximity to fine cellulose fibrils). These data provide deeper insights into the effects of paper functionalization with a copolymer and aid in understanding how these agents ultimately influence the local and overall properties of paper.
authors.affiliation: †Physics of Surfaces, Institute of Materials Science, Technische Universität Darmstadt, Alarich-Weiss-Straße 2, 64287 Darmstadt, Germany.|‡Center of Smart Interfaces, Technische Universität Darmstadt, Alarich-Weiss-Straße 10, 64287 Darmstadt, Germany.
authors.forename: Marek
authors.initials: M
authors.lastname: Janko
authors.affiliation: §Macromolecular Chemistry and Paper Chemistry, Department of Chemistry, Technische Universität Darmstadt, Alarich-Weiss-Straße 8, D-64287 Darmstadt, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Jocher
authors.affiliation: ‡Center of Smart Interfaces, Technische Universität Darmstadt, Alarich-Weiss-Straße 10, 64287 Darmstadt, Germany.|§Macromolecular Chemistry and Paper Chemistry, Department of Chemistry, Technische Universität Darmstadt, Alarich-Weiss-Straße 8, D-64287 Darmstadt, Germany.
authors.forename: Alexander
authors.initials: A
authors.lastname: Boehm
authors.affiliation: ∥Membrane Dynamics, Department of Biology, Technische Universität Darmstadt, Schnittspahnstraße 3-5, 64287 Darmstadt, Germany.
authors.forename: Laura
authors.initials: L
authors.lastname: Babel
authors.affiliation: ∥Membrane Dynamics, Department of Biology, Technische Universität Darmstadt, Schnittspahnstraße 3-5, 64287 Darmstadt, Germany.
authors.forename: Steven
authors.initials: S
authors.lastname: Bump
authors.affiliation: ‡Center of Smart Interfaces, Technische Universität Darmstadt, Alarich-Weiss-Straße 10, 64287 Darmstadt, Germany.|§Macromolecular Chemistry and Paper Chemistry, Department of Chemistry, Technische Universität Darmstadt, Alarich-Weiss-Straße 8, D-64287 Darmstadt, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Biesalski
authors.affiliation: ∥Membrane Dynamics, Department of Biology, Technische Universität Darmstadt, Schnittspahnstraße 3-5, 64287 Darmstadt, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Meckel
authors.affiliation: †Physics of Surfaces, Institute of Materials Science, Technische Universität Darmstadt, Alarich-Weiss-Straße 2, 64287 Darmstadt, Germany.|‡Center of Smart Interfaces, Technische Universität Darmstadt, Alarich-Weiss-Straße 10, 64287 Darmstadt, Germany.
authors.forename: Robert W
authors.initials: RW
authors.lastname: Stark
mesh_terms: D001577:Benzophenones / Q000737:chemistry; D002482:Cellulose / Q000648:ultrastructure*; D047569:Laser Scanning Cytometry / Q000379:methods*; D008689:Methacrylates / Q000737:chemistry; D010209:Paper; D055668:Photochemical Processes; D017319:Photosensitizing Agents / Q000737:chemistry; D059027:Recycling; D013059:Spectrum Analysis, Raman / Q000379:methods*
chemical_list: D001577:Benzophenones; D008689:Methacrylates; D017319:Photosensitizing Agents; C047723:benzophenone; D002482:Cellulose