Abstract:A thermo-responsive cellulose-based material (cellulose-g-PNIPAAm) was prepared by grafting N-isopropylacrylamide (NIPAAm) onto bagasse pulp cellulose via Ce (IV)-initiated free radical polymerization. The surfaces of the obtained cellulose-g-PNIPAAm paper showed a rapid wettability conversion from being hydrophilic (water contact angles (WCA) of 0 • ) at 25 • C to becoming hydrophobic (WCA of 134.2 • ) at 45 • C. Furthermore, the thermo-responsive mechanism of cellulose-g-PNIPAAm was examined by the in situ variable-temperature 13 C NMR, 1 H NMR and AFM analysis. At the same time, the resulting cellulose paper was applied for a switchable separation of oil/water mixtures. Water can pass through the paper under 45 • C, while oil is kept on the paper. When the temperature is above 45 • C, oil can permeate through the paper, while water cannot pass through the water. Moreover, the paper exhibited excellent regeneration performance after five cycles and maintained its switchable wettability.
Novel nanosized biomass-based pH-responsive
cellulose nanofibers
(CNF-PEI) with excellent biocompatibility were tailored by grafting
polyethylenimine (PEI) onto carboxylated cellulose nanofibers (CNF-COOH);
the active site (−COOH, 0.96 mmol/g) was anchored on cellulose
nanofibers (CNFs) to introduce PEI with a high density (10.57 mmol/g)
of amino groups. The as-prepared CNF-PEI not only maintained the good
properties of CNFs but also possessed excellent biocompatibility and
pH-responsive properties, offering interesting possibilities for pH-induced
sustained drug release and medical dressing. The CNF-PEI showed rapid
wettability conversion from hydrophilic, underwater superoleophobic
(WCA = 20.7°, OCA = 159.3°) to hydrophobic, superoleophilic
(WCA = 129.6°, OCA = 29.7°) in response to pH change from
acidic conditions to alkaline conditions. The antibacterial activity
of CNF-PEI toward Escherichia coli and Listeria
monocytogenes was 100% and 94.6% under acidic conditions,
respectively. Furthermore, the pH-responsive mechanism of CNF-PEI
was revealed by XPS, 13C NMR, 1H NMR, and AFM
analyses.
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