For the modification of medically useful biomaterials from bacterially synthesized cellulose, fleeces of Acetobacter xylinum have been produced in the presence of 0.5, 1.0, and 2.0% (m/v) carboxymethylcellulose (CMC), methylcellulose (MC), and poly(vinyl alcohol) (PVA), respectively, in the Hestrin‐Schramm culture medium. The incorporation of the water‐soluble polymers into cellulose and their influence on the structure, crystal modifications, and material properties are described. With IR and solid‐state 13C NMR spectroscopy of the fleeces, the presence of the cellulose ethers and an increase in the amorphous parts of the cellulose modifications (NMR results) have been detected. The incorporation is represented by a higher product yield, too. As demonstrated by scanning electron microscopy, a porelike cellulose network structure forms in the presence of CMC and MC. This modified structure increases the water retention ability (expressed as the water content), the ion absorption capacity, and the remaining nitrogen‐containing residues from the culture medium or bacteria cells. The water content of bacterial cellulose (BC) in the never dried state and the freeze‐dried, reswollen state can be controlled by the CMC concentration in the culture solution. The freeze‐dried, reswollen BC‐CMC (2.0%) contains 96% water after centrifugation, whereas standard BC has only 73%. About 98% water is included in a BC‐MC composite in the wet state, and about 93% is included in the reswollen state synthesized in the presence of 0.5, 1.0, or 2.0% MC. These biomaterial composites can be stored in the dried state and reswollen before use, reaching a higher water absorption than pure, never dried BC. The copper ion capacity of BC‐CMC composites increases proportionally with the added amount of CMC. BC‐CMC (0.5%) can absorb 3 times more copper ions than original BC. In the case of 0.5 and 1.0% PVA additions to the culture solution, this polymer cannot be detected in the cellulose fleeces after they are washed. Nevertheless the presence of PVA in the culture medium effects a decreased product yield, a retention of nitrogen‐containing residues in the material during purification, a reduced water absorption ability, and a slightly higher copper ion capacity in comparison with original BC. The water content of freeze‐dried, reswollen BC‐PVA (0.5%) is only 62%. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 463–470, 2004
The bulk use of renewable polymers is currently largely limited to cellulose and, less significantly, hemicelluloses. Technical lignins are only applied in novel materials to a rather limited extent, although bulk lignin utilization is a worldwide research object. Native lignins, which belong to the second or third most abundant biopolymers of terrestrial plants, are mostly used in the form of technical lignins from wood pulping processes; they are employed in low-performance sectors or simply burnt for the generation of energy. Technical lignins are available in huge quantities and have a large application potential, mainly in areas where their aromatic nature is of relevance. This review presents the state of the art of foamed lignin-based polymers (lignofoams) as high-performance insulation materials. In the focus of this presentation are the fundamental foaming principles and influential agents that have an improvement potential concerning the matrix interactions between technical lignins (including lignosulfonates) and a copolymer in foam composites. The different approaches for foam preparation are critically compared. In general, the reviewed papers disclose that the lignin part in foams should be less than 37%. There are significant difficulties to improve the properties of lignofoams, and thus intensive research is needed to find better formulations and new technologies.
Unter Verwendung von drei unterschiedlichen Celluloseproben (Buchensulfitzellstoff, Baumwoll‐Linters, hydrolytisch abgebaute Linters) vor und nach Aktivierung mit flüssigem Ammoniak wird der Einfluß der physikalischen Struktur der Cellulose auf deren Auflösung in binären Gemischen von N‐Methylmorpholin‐N‐oxid mit DMSO, DMF, Nitroben zen oder N‐Methylcaprolactam untersucht. Im Bereich partieller Löslichkeit werden die Rückstände mittels DP, LODP und Röntgendiagramm charakterisiert. Die Ergebnisse werden hinsichtlich der Relevanz der Einflußgrößen Fibrillarstruktur, Ordnungszustand, DP und Xylan‐Gehalt der Celluloseproben diskutiert.
Professor Dr. Josef Schurz zum 65. Geburtstag gewidmet Es werden Aussagen zu den Wechselwirkungen zwischen N-Methylmorpholin-N-oxid und einer zweiten protischen oder aprotischen Losungsmittelkomponente fur Cellulose getroffen. Als Untcrsuchungsmethoden dienten DSC-, 'H-NMR-, FTIR-und RWWS-Messungen. Um den Celluloselosemechanismus zu erklaren, wurden einige Modellsubstanzen rnit OH-Gruppen in binaren Systemen rnit NMMNO untersucht. Die hier und in fruheren Mitteilungen erhaltenen experimentellen Ergebnisse werden hinsichtlich der Losewirkung von Mischungen aus NMMNO .I H,O und unterschiedlichen Zweitkomponenten gegenuber Cellulose zusammenfassend diskutiert. mccneaoeanu pacmeopenus ~e~znwn03b~ 8 6unapnaix anpomuuecmx cucmeaax. 3 . C00624. Nccnedoeanm eaaumoaefic m e u mmcay ornaefibnacau komnonenmuu pacmeopumeneii an8 yennwnoaac u 06 yaicaenm o mexanuaae pacmeopenm PaCCMaTpHBaeTCH B3aWMOAe&CTBHe MeHtAY N -M e T H J I M O p~O J I H H -N -O K C~A O M (NMMNO) H BTOPHM IIPOTHYeCKHM HJIH aIIpOTHYeCKHM KOMIIOHeHTOM PaCTBOpllTeJIH AJIH UeJIJIIoJI03E.I. MCCJIeAOBaHHH IIpOBOAHJIHCb C lXOMOLQbI0 ACH, 'H-HMP, @T~~-CIIeKTpOCKOIIHH I4 MeTOAOM PaCCeHHElH PeHTreHOBCHHX JIyYei H a 6 o n b r u~x YrJIaX. q~0 6 b 1 BPHCHHTb MeXaHH3M PaCTBOPeHHH qeJIJIIOJI03bI HCCJIeAOBaJIH HeKOTOpbIe MOAeJIbHbIe BeLQeCTBa C OH-rpynnaME B ~IIHIPHUX CHCTeMaX C NMMNO. nOJIyYeHHbIe B A a H H O i W B IIpeAbIAyQHX patjo~ax pe3yJIbTaTbI 0 6 c y x f l a 1 0~c~ OTHOCHTeJIbHO paCTBOpFIIOQe2f CnOCO6HOCTH AJIH qeJIJIIoJI03bI CMeCefi NMMNO * 1 HzO C paaJIH'4HbIMki KOMIIOHeHTaMH. Investigation of the solution of cellulose in binary aprotic systems. 3rd Comm. Study of the interaction between the individual solvent components and discussion of the solution mechanismInteractions between N-methylmorpholine-N-oxide and a second protic or aprotic solvent component for cellulose are considered. For the experimental investigations DSC, lH-NMR spectroscopy, FTIR spectroscopy, and WAXS were employed. To obtain informations on the mechanism of cellulose dissolution, some model compounds containing OHgroups were investigated in the appropriate binary solvent systems. The results obtained here and in our previous publications are discussed with regard to the solvent action of binary systems with NMMNO.1 H,O on cellulose.
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