1 research outputs found
Cross-Linking Cellulosic Fibers with Photoreactive Polymers: Visualization with Confocal Raman and Fluorescence Microscopy
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-<i>co</i>-methacrylate-benzophenone
PÂ(DMAA-<i>co</i>-MABP) copolymers with defined amounts of
photoreactive benzophenone moieties in model paper sheets. Raman microscopy
was used for the unambiguous identification of PÂ(DMAA-<i>co</i>-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