Cellulose (2021) 28:5775–5791
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case of IPA and BuOH, the copolymer can be observed as sleeve-like-aggregates both at as well as away from fiber–fiber crossings, as can be seen in Fig. 8f, i, respectively. However, as they are not fully wrapping around the fiber crossing points and due to the hydrophilic nature of the cross-linked polymer, the Fig. 8 CLSM image stacks of paper samples combined to 3D- images, with the fluorescently labelled copolymer applied out of H 2 O( a – c ), IPA( d – f )andBuOH( g – i ), respectively, beforehand. The images show a top view of cellulose fibers stained by CW ( a , d , g ), PDMAA labelled by RhB ( b , e , h ) and overlays of the latter ( c , f , i ). For H 2 O-impregnation the images show the homogeneous spatial distribution of copolymer across the whole
protection of those crossing points from moisture according to a protection mechanism can be neglected. While those aggregates are able to form cross-links between adjacent fibers, the remaining fiber surface, without any fibers in close proximity, is virtually free of adsorbed copolymer—at least as far as fluorescence fiber network. Overlays of both fluorescent signals appear as blue in 3D-renderings. In contrast, the IPA -impregnated samples show an inhomogeneously distributed copolymer with agglomeration at fiber–fiber crossings, while the BuOH - impregnated samples show a more homogeneous distribution, but not on the single fiber scale comparable to H 2 O - impregna- tion. Scale bar is 100 l m
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