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Kraft pulp is the most common and economically advantageous raw material for making cellulose nanofibers (CNFs). However, when kraft pulp is subjected to mechanical fibrillation, unfibrillated pulp always remains, even though the pulp is undried. In this study, the effect of the kraft pulping process on the fibrillation of undried pulp was studied. The fibrillation ability was compared with that of undried pulp prepared using Wise method and alkaline treatment. Suspensions of undried pulps were mechanically fibrillated with a high-speed blender for different durations. The degree of fibrillation of pulps was evaluated using sedimentation, morphologies from field emission scanning electron microscopy, specific surface area, and water retention values. Every analysis showed that undried, kraft-based pulp was less fibrillated than undried, wise-based pulp. These results suggested that the kraft cooking process at high temperature hindered the fibrillation of pulp. This might be related to the aggregation occur in cellulose.

We report an integrated production process that simultaneously nanofibrillates dried pulp and uniformly disperses cellulose nanofibers (CNFs) in resins. Refiner-treated pulp were modified using alkenyl succinic anhydride (ASA) in N-Methyl-2-pyrrolidone (NMP). The ASA treated pulp with DS 0, 0.22, 0.43 and 0.57 was mixed with maleic anhydride-grafted polypropylene (MAPP) powder, CaCO3 and high density polyethylene (HDPE) powder (pulp content: 10 wt%). The mixture was melt-extruded at 140 °C with HDPE. The dumbbell-shaped specimens were prepared using injection molding. The SEM images of refiner-treated pulp (DS 0.43) and previously nanofibrillated CNFs (DS 0.44) using a bead mill as a comparison, both of which were extracted from the melt compounded composites, showed comparable degrees of nanofibrillation. The highest mechanical reinforcing efficiency was obtained at DS 0.43, which was shown to exhibit the most fibrillated morphology. The tensile modulus increased from 1.08 GPa for neat HDPE, to 3.46 GPa. The tensile strength also increased from 23 MPa (neat HDPE) to 56 MPa. The mechanical properties were very similar to the bead mill-fibrillated CNF-reinforced composite. This is the first report of nanofibrillation of dried pulp with uniform CNF dispersion into hydrophobic HDPE. We have termed the process the Pulp Direct-Kneading Method.

The study demonstrated the improvement in the resistance of nanocellulose against thermally-induced depolymerization by esterification with benzoyl (BNZ) and pivaloyl (PIV). The change in the degree of polymerization (DP) and molecular weight distribution (MWD) after thermal treatment in nitrogen and in air was investigated using viscometry and gel permeation chromatography. BNZ and PIV nanocellulose esters without α-hydrogens gave higher DP and narrower MWD than pure bacterial cellulose; and the acetyl and myristoyl esters, which possess α-hydrogens. Results also showed that when depolymerization is suppressed, thermal discoloration is also reduced. Resistance against depolymerization inhibits the formation of reducing ends which can be active sites for thermal discoloration. Finally, the findings suggest that benzoylation and pivaloylation can be an excellent modification technique to improve the thermal stability of nanocellulose.

It is a challenging task to reinforce polyamide 6 (PA6) using nanofibrillated cellulose because the melting temperature of PA6 is high and nanofibrillated cellulose degrade at high temperatures. First, soft wood kraft pulps were acetylated (Ac) to improve the heat resistance. The weight loss temperature of the pulps increased by 31 °C through acetylation (DS = 0.64). It was evident that the melt compounding process using a twin-screw extruder allowed for nanofibrillation of the Ac-pulps. Ac-nanofibrillated cellulose reinforced PA6 showed a high storage modulus, which suggests that the Ac-nanofibrillated cellulose formed a network in the PA6 matrix. The Ac-nanofibrillated cellulose improved the bending modulus from 2.22 GPa (neat PA6) to 5.43 GPa, the strength from 91.2 MPa to 154 MPa, the coefficient of thermal expansion from 110.9 ppm/K to 24.3 ppm/K, and the heat-deflection temperature from 85.7 °C to 166.6 °C. The melt compounding of Ac-pulps with PA6 using a twin-screw extruder facilitates the commercial production of nanofibrillated cellulose reinforced PA6.

Hydrophobic cellulose nanofibers (CNFs) were prepared by surface modification using alkenyl succinic anhydride (ASA). The hydrophobicity of CNFs was varied by changing the degree of substitution (DS) from 0 to 0.83. Modified CNFs were mixed with high-density polyethylene (HDPE) using a twin-screw extruder and the resulting composites were injection molded. The tensile properties initially improved with increasing DS up to ∼0.3–0.5, and then decreased with further substitution. The tensile strength and modulus of 10 wt.% HDPE/CNF composites containing 8.8 wt.% ASA (DS: 0.44) were 43.4 MPa and 1.97 GPa, respectively. These values were both almost 70% higher than those of composites containing unmodified CNF, and 100% and 86% higher, respectively, than those for pure HDPE. X-ray computed tomography measurements showed that CNFs modified with a DS of 0.44 were dispersed uniformly within the resin matrix, whilst unmodified CNFs and those modified with a DS of 0.77 agglomerated within the composites.

6-Azafulleroid-6-deoxy-2,3-di- O -myristoylcellulose ( 3 ) was synthesized from 6-azido-6-deoxycellulose ( 1 ) by two reaction steps. The myristoylation of compound 1 with myristoyl chloride/pyridine proceeded smoothly to give 6-azido-6-deoxy-2,3-di- O -myristoylcellulose ( 2 ) in 97.0% yield. The reaction of compound 2 with fullerene (C 60 ) was carried out by microwave heating to afford compound 3 in high yield. It was found from FT-IR, 13 C NMR, UV–vis, differential pulse voltammetry (DPV), SEC analyses that compound 3 was the expected C 60 -containing polymer. Consequently, maximum degree of substitution of C 60 (DS C60 ) of compound 3 was 0.33.

The incompatibility between cellulose fibers and hydrophobic polymers has presented a major obstacle for the fabrication of composites and nanocomposites. In this study, we applied a one-time grinder treatment to disintegrate chemi-thermomechanical pulp (CTMP) and obtained micro- to nano-meter-sized lamellar or fibrous fragments. The CTMP fragments were composed of cellulose microfibrils with high aspect ratios encased in matrix substances including hydrophobic lignin. Furthermore, we produced compression-molded products from the CTMP fragments by thermally plasticizing lignin without any adhesives or resins. The molded products pressed at 180 °C exhibited a plastic-like gloss on the surface and a high bending strength, 221 MPa, which greatly exceeded that of the conventional plant-based binderless boards. The molded products produced here are a novel form of ideal cellulose nanocomposite, which exploited the inherent compatibility between cellulose microfibrils and matrix substances present in CTMP fragments.

Microwave heating was applied to the reactions involved in the synthesis of 6-amino-6-deoxycellulose, 4. These included, cellulose solubilization, bromination at C-6, displacement of bromine with azide ion, and reduction of the azido group to an amino group. Compared to conventional heating, this approach had the advantages of shortening reaction times and retaining the degree of polymerization of 4.

Novel chitosan derivatives with UV-curable functional groups, such as 3-methoxy-4-(2-hydroxy-3-methacryloyloxypropoxy)benzyl, 3,4-bis(2-hydroxy-3-methacryloyloxypropoxy)benzyl, 3-methoxy-4-methacryloyloxybenzyl, and 3,5-dimethacryloyloxybenzyl groups, were prepared. Introduction of photosensitive functional groups to chitosan was accomplished by reductive N -alkylation via Schiff’s bases using corresponding photosensitive aldehydes. Compared to starting chitosan, UV-curable chitosan derivatives showed better solubility in several organic solvents, such as DMSO and 70% methacrylic acid. The solubility of these compounds increased with an increase in the degree of substitution of the N -alkyl side chains. After UV irradiation for 20 s under a high-pressure mercury lamp at a distance of 15 cm from the samples, acidic methanol solutions of these derivatives were transformed to gels in the presence of photo-initiator, and their dried films adsorbed palladium (II) at pH 1.1 and pH 5.3. The UV-curable chitosan derivatives were successfully used as coating materials for electroless plating on non-conductive substances.

6-Amino-6-deoxycellulose (4) was synthesized from cellulose by three reaction steps, namely bromination at C-6, displacement of bromine by azide ion, and reduction of the azide group to amino group, in 67% overall yield. The 13C NMR spectrum of compound 4 supports the expected structure for 6-amino-6-deoxycellulose. The degree of substitution of compound 4 was 0.96.

The synthetic route to 3- O -benzyl-6- O -pivaloyl-α- d -glucopyranose 1,2,4-orthopivalate ( 1 ), which was previously established, was shortened by introducing two novel reactions, regioselective pivaloylation with dibutyltin oxide in toluene for the regioselective activation of hydroxyl groups, and intramolecular orthoesterification with benzenesulfonyl chloride and triethylamine in dichloromethane. Compound 1 was obtained in 58.8% overall yield from commercially available 1,2:5,6-di- O -isopropylidene-α- d -glucopyranose ( 2 ) via four reaction steps.

Two novel methods for the syntheses of 1,4-anhydro-3- O -benzyl-2- O -pivaloyl- ( 1 ) and 2- O -acetyl-1,4-anhydro-3- O -benzyl- α - d -xylopyranose ( 2 ), starting materials for synthesizing stereoregular β -( 1 → 5)-xylofuranan by ring-opening polymerization are reported. Both synthetic routes start from d -xylopyranose, involve nine reaction steps, and give approximately 30–35% overall yields. The key reaction in the novel synthetic routes is the intramolecular nucleophilic attack of C-1 oxyanion on the C-5 position of 3- O -benzyl-5- O -( p -toluenesulfonyl)- α - d -xylofuranose ( 10 ), resulting in 1,5-acetal bond formation in high yield. The present synthetic routes enable us to prepare 1,4-anhydro- α - d -xylopyranose derivatives having different substituents at the 2- O - and the 3- O -positions.

In order to synthesize ( 1 → 5)-β- d -galactofuranan by rig-opening polymerization, 3,6-di-O-benzyl-α- d -galactofuranose 1,2,5-orthopivalate (9) the most appropriate monomer was synthesized from d -galactose via 10 reaction steps. Novel intramolecular orthoesterification, which is a key reaction for sythesizing compound 9, was accomplished by treatment of 5-O-monocholoacetyl-2,3,6-tri-O-pivaloyl- d -galactofuranosyl chloride (6) with thiourea in pyridine at 80 °C to give the expected orthoester (7) in good yield without any side reactions.

Effects of environmental factors on two-stage co-precipitation of tetragalloylglucose with three different proteins [bovine serum albumin (BSA), lysozyme, and myoglobin] were investigated. Factors such as pH, temperature, and ionic strength, mainly affected the second precipitation stage. On the other hand, protein concentration mainly affected the initial complexation stage. Precipitability of the galloylglucose-protein complexes is directly related to the solubility of the original protein under each environmental condition.

Solubility of bovine serum albumin (BSA) (P) precipitated with tetragalloylglucose (T) was investigated by successive washing over the pH range of 3–7. The solubility was highly dependent on pH (4 T/P(R) (pH 4 and 5), the precipitates were very stable, while when NSB 15(tetra) > 0(tri)].

Synthese d'-1-O-allyl-3-O-benzyl-2,4,6-tri-O-acetyl (ou 1-O-allyl-tetra-O-acetyl) glucopyranoside a partir d'3-O-benzyl-tetra-O-acetyl (ou per-O-acetyl) glucopyranose, d'ethyle ether-trifluoroborane et de prop-2-en-1-ol

This study reexamined our contention that singlet oxygen (1O2) plays a role in the fungal degradation of lignin (BBRC 102(1981)484). Cultures of Phanerochaete chrysosporium and a photochemical 1O2-generating system (riboflavin/light/O2) cleaved a lignin substructure model compound, 1,2-bis(4-methoxyphenyl)propane-1,3-diol (I), by indistinguishable mechanisms. However, the rate of cleavage of I in D2O was the same as in H2O in the photochemical 1O2-generating system, indicating that 1O2 was not involved. Furthermore, products formed from I in a chemical system for generating 1O2 (H2O2 + NaOCl) differed from those produced by cultures or the photochemical system. It is concluded that 1O2 is not responsible for cleavage of I or related compounds in the fungal cultures or in the photochemical system.

The metabolism of a lignin substructure model compound, 1,2-bis(3-methoxy-4-ethoxyphenyl)propane-1,3-diol (Ia) in ligninolytic cultures of Phanerochaete chrysosporium was studied to help elucidate the biochemical mechanism of lignin degradation. The primary reaction was cleavage of the model compound between C 1 and C 2 of the propane moiety to produce 1-(3-methoxy-4-ethoxyphenyl)ethane-1,2-diol and a C 6 -C 1 product (probably 3-methoxy-4-ethoxybenzaldehyde). Other identified products arose secondarily; all were further metabolized. Even though the model compound was a mixture of four stereoisomers, no stereoselectivity was observed in its metabolism. In cultures under 18 O 2 , the initial cleavage produced the diol product with ≈70% enrichment by 18 O in the benzyl alcohol group. The diol was a mixture of the two possible enantiomers, and the O 2 -derived hydroxyl was incorporated at the asymmetric (benzyl) carbon. (Limited optical activity in the diol was traced to selective further metabolism of the D form.) These results show that the primary cleavage reaction lacked stereospecificity and was primarily oxygenative, implicating a nonspecific oxygenase or a nonenzymatic reaction involving activated oxygen. Preliminary experiments demonstrated no cell homogenate activity against Ia.

Previous research established that lignin substructure model compounds of the non-phenolic β-1 type (R-C α HOH-C β HR′-C γ H 2 OH, in which R,R′ = O-alkyl) are cleaved between C α and C β by Phanerochaete chrysosporium . The C β -derived product is a racemic phenylglycol (R′-CHOH-CH 2 OH) in which the benzyl hydroxyl oxygen atom is derived from molecular oxygen. Investigations described here have established, through the use of an isotope-trapping technique and the same organism, that the C α -derived product is the aromatic aldehyde (R-C α HO); this aldehyde is rapidly reduced in cultures to the corresponding alcohol. A β-1 substrate without the C γ H 2 OH moiety is also cleaved, showing that the C γ -group is not required. A β-1 substrate with a C α -carbonyl group is only slowly degraded (to polar products), probably not via C α -C β cleavage. Mass spectrometric analysis of the products formed from deuterated β-1 substrates established that hydrogen (deuterium) atoms at C α and at C β are not lost during C α -C β cleavage. These results establish that neither C α -oxidation, C β -hydroxylation nor formation of a C α -C β double bond occurs prior to C α -C β cleavage, and that cleavage does not involve C γ . A concerted mechanism is indicated, in which C β -hydroxylation, with a hydroxyl derived from O 2 , occurs simultaneously with, or after, C α -C β cleavage.