PRODUCTION OF CELLULOSE NANOCRYSTALS BY HYDROLYSIS IN MIXTURE  OF HYDROCHLORIC AND NITRIC ACIDS

In this work, cellulose nanocrystals (CNC) have been produced by hydrothermal method in a mixture of hydrochloric and nitric acids in molar ratios of 8:2, 7:3, 6:4 and 5:5. Hydrolysis of sulphate cellulose in the mixtures of nitric and hydrochloric acids was conducted in a sealed thick-walled stainless steel vessel with a teflon insert for 3 h at 110 °С. Properties of CNC have been characterized by applying different methods: elemental analysis, thermogravimetric analysis, IR spectroscopy, polarization optical microscopy, scanning electron microscopy, and dynamic light scattering. Yield of CNC, size and charge of the CNC particles, degree of polymerization, temperature of thermal destruction have been determined, and morphology of the CNC samples has been characterized. The highest CNC yield (32%) has been observed at a 7:3 ratio of nitric and hydrochloric acids. It has been established that the CNC particles are spherical and have an average size of 60-80 nm. An assumption has been made that presence of a strong oxidant (nitric acid) may cause hydrolysis of both amorphous and crystalline (in part) regions of cellulose, which affects the final shape of the CNC particles. It has been shown that the hydrolysis in a mixture of nitric and hydrochloric acids causes an oxidation of primary hydroxyl groups of the cellulose pyranose ring and formation of surface carboxyl groups. The CNC aqueous suspensions demonstrate high colloidal stability due to a rather high surface charge. It is noted that the CNC thermal stability is much higher than that of the CNC samples obtained by the standard sulfuric acid hydrolysis: the temperature of thermal destruction increases by 130-148 °С.

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On the Para/Ortho Reactivity of Isocyanate Groups during the Carbamation of Cellulose Nanocrystals Using 2,4-Toluene Diisocyanate

Polymers ◽

10.3390/polym11071164 ◽

2019 ◽

Vol 11 (7) ◽

pp. 1164 ◽

Cited By ~ 8

Author(s):

Hatem Abushammala

Keyword(s):

Cellulose Nanocrystals ◽

Negative Impact ◽

Toluene Diisocyanate ◽

Molar Ratio ◽

Hydroxyl Groups ◽

Reaction Conditions ◽

Surface Hydroxyl ◽

Molar Ratios ◽

Hydrolysis Method ◽

Surface Hydroxyl Groups

2,4-toluene diisocyanate (TDI) has been commonly used to bind molecules and polymers onto the surface of cellulose nanocrystals (CNCs). Such a process usually involves two steps: (1) the more reactive para-isocyanates (p-NCOs) of TDI are reacted with the surface hydroxyl groups of CNCs then (2) the ortho-isocyanates (o-NCOs) are reacted with certain desired molecules. During the first reaction, an ideal para/ortho selectivity could be impossible to achieve, as o-NCOs are not fully unreactive. Therefore, there is a need to better understand the reaction between CNCs and TDI towards a maximum para/ortho selectivity. For that goal, CNCs were reacted with TDI under varying temperatures (35–75 °C) and TDI/CNCs molar ratios (1–5). The amount of the reacted TDI was estimated using elemental analysis while the free o-NCO groups were quantified following the hydrolysis method of Abushammala. The results showed that temperature had a negative impact on para/ortho selectivity while TDI/CNCs molar ratio improved it. A maximum selectivity of 93% was achieved using a temperature of 35 °C and a molar ratio of 3. This is a three-fold improvement to that using the traditional reaction conditions (75 °C and molar ratio of 1).

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Preparation and Surface Functionalization of Carboxylated Cellulose Nanocrystals

Nanomaterials ◽

10.3390/nano11071641 ◽

2021 ◽

Vol 11 (7) ◽

pp. 1641

Author(s):

Edmond Lam ◽

Usha D. Hemraz

Keyword(s):

Sulfuric Acid ◽

Functional Properties ◽

Surface Functionalization ◽

Cellulose Nanocrystals ◽

Recent Progress ◽

Colloidal Stability ◽

Industrial Applications ◽

Predominant Form ◽

Hydrolysis Of Cellulose ◽

Hydrolysis Of

In recent years, cellulose nanocrystals (CNCs) have emerged as a leading biomass-based nanomaterial owing to their unique functional properties and sustainable resourcing. Sulfated cellulose nanocrystals (sCNCs), produced by sulfuric acid-assisted hydrolysis of cellulose, is currently the predominant form of this class of nanomaterial; its utilization leads the way in terms of CNC commercialization activities and industrial applications. The functional properties, including high crystallinity, colloidal stability, and uniform nanoscale dimensions, can also be attained through carboxylated cellulose nanocrystals (cCNCs). Herein, we review recent progress in methods and feedstock materials for producing cCNCs, describe their functional properties, and discuss the initial successes in their applications. Comparisons are made to sCNCs to highlight some of the inherent advantages that cCNCs may possess in similar applications.

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Properties and Applications of Modified Bacterial Cellulose-Based Materials

Current Nanoscience ◽

10.2174/1573413716999201106145528 ◽

2020 ◽

Vol 16 ◽

Author(s):

Munair Badshah ◽

Hanif Ullah ◽

Fazli Wahid ◽

Taous Khan

Keyword(s):

Surface Modification ◽

Bacterial Cellulose ◽

Degree Of Polymerization ◽

Biomedical Science ◽

Hydroxyl Groups ◽

Market Demand ◽

Ideal Candidate ◽

Fibrous Network ◽

Potential Applications ◽

Surface Modification Techniques

Background: Bacterial cellulose (BC) is purest form of cellulose as it is free from pactin, lignin, hemicellulose and other active constituents associated with cellulose derived from plant sources. High biocompatibility and easy molding into desired shape make BC an ideal candidate for applications in biomedical field such as tissue engineering, wound healing and bone regeneration. In addition to this, BC has been widely studied for applications in the delivery of proteins and drugs in various forms via different routes. However, BC lacks therapeutic properties and resistance to free movement of small molecules i.e., gases and solvents. Therefore, modification of BC is required to meet the research ad market demand. Methods: We have searched the updated data relevant to as-synthesized and modified BC, properties and applications in various fields using Web of science, Science direct, Google and PubMed. Results: As-synthesized BC possesses properties such as high crystallinity, well organized fibrous network, higher degree of polymerization, and ability of being produced in swollen form. The large surface area with abundance of free accessible hydroxyl groups makes BC an ideal candidate for carrying out surface functionalization to enhance its features. The various reported surface modification techniques including, but not limited to, are amination, methylation and acetylation. Conclusion: In this review, we have highlighted various approaches made for BC surface modification. We have also reported enhancement in the properties of modified BC and potential applications in different fields ranging from biomedical science to drug delivery and paper-making to various electronic devices.

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Kinetics of hydrolysis of peroxodisulphate ions in acidic medium to peroxomonosulphuric acid

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19811229 ◽

1981 ◽

Vol 46 (5) ◽

pp. 1229-1236 ◽

Cited By ~ 7

Author(s):

Jan Balej ◽

Milada Thumová

Keyword(s):

Ionic Strength ◽

Rate Constants ◽

Acidic Medium ◽

Measured Data ◽

Molar Ratios ◽

Starting Solution ◽

Kinetics Of Hydrolysis ◽

Rate Of Hydrolysis ◽

Kinetics Of ◽

Hydrolysis Of

The rate of hydrolysis of S2O82- ions in acidic medium to peroxomonosulphuric acid was measured at 20 and 30 °C. The composition of the starting solution corresponded to the anolyte flowing out from an electrolyser for production of this acid or its ammonium salt at various degrees of conversion and starting molar ratios of sulphuric acid to ammonium sulphate. The measured data served to calculate the rate constants at both temperatures on the basis of the earlier proposed mechanism of the hydrolysis, and their dependence on the ionic strength was studied.

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Osseointegrating and phase-oriented micro-arc-oxidized titanium dioxide bone implants

Journal of Applied Biomaterials & Functional Materials ◽

10.1177/22808000211006878 ◽

2021 ◽

Vol 19 ◽

pp. 228080002110068

Author(s):

Hsien-Te Chen ◽

Hsin-I Lin ◽

Chi-Jen Chung ◽

Chih-Hsin Tang ◽

Ju-Liang He

Keyword(s):

Titanium Dioxide ◽

High Surface ◽

Cell Activity ◽

Active Surface ◽

Rutile Phase ◽

Hydroxyl Groups ◽

Bone Implant ◽

Implant System

Here, we present a bone implant system of phase-oriented titanium dioxide (TiO2) fabricated by the micro-arc oxidation method (MAO) on β-Ti to facilitate improved osseointegration. This (101) rutile-phase-dominant MAO TiO2 (R-TiO2) is biocompatible due to its high surface roughness, bone-mimetic structure, and preferential crystalline orientation. Furthermore, (101) R-TiO2 possesses active and abundant hydroxyl groups that play a significant role in enhancing hydroxyapatite formation and cell adhesion and promote cell activity leading to osseointegration. The implants had been elicited their favorable cellular behavior in vitro in the previous publications; in addition, they exhibit excellent shear strength and promote bone–implant contact, osteogenesis, and tissue formation in vivo. Hence, it can be concluded that this MAO R-TiO2 bone implant system provides a favorable active surface for efficient osseointegration and is suitable for clinical applications.

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Adjustment of Hydrophobic Properties of Cellulose Materials

Polymers ◽

10.3390/polym13081241 ◽

2021 ◽

Vol 13 (8) ◽

pp. 1241

Author(s):

Michael Ioelovich

Keyword(s):

Ester Group ◽

Hydroxyl Groups ◽

Chemical Methods ◽

Hydrophobic Properties ◽

Cellulose Esters ◽

Cellulose Modification ◽

Polar Groups ◽

Polar Substituents ◽

Hydrolysis Of ◽

Cellulose Materials

In this study, physicochemical and chemical methods of cellulose modification were used to increase the hydrophobicity of this natural semicrystalline biopolymer. It has been shown that acid hydrolysis of the initial cellulose increases its crystallinity, which improves hydrophobicity, but only to a small extent. A more significant hydrophobization effect was observed after chemical modification by esterification, when polar hydroxyl groups of cellulose were replaced by non-polar substituents. The esterification process was accompanied by the disruption of the crystalline structure of cellulose and its transformation into the mesomorphous structure of cellulose esters. It was found that the replacement of cellulose hydroxyls with ester groups leads to a significant increase in the hydrophobicity of the resulting polymer. Moreover, the increase of the number of non-polar groups in the ester substituent contributes to rise in hydrophobicity of cellulose derivative. Depending on the type of ester group, the hydrophobicity increased in the following order: acetate < propionate < butyrate. Therefore, tributyrate cellulose (TBC) demonstrated the most hydrophobicity among all studied samples. In addition, the mixed ester, triacetobutyrate cellulose (TAB), also showed a sufficiently high hydrophobicity. The promising performance properties of hydrophobic cellulose esters, TBC and TAB, were also demonstrated.

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Processive action of cellobiohydrolase Cel7A from Trichoderma reesei is revealed as ‘burst’ kinetics on fluorescent polymeric model substrates

Biochemical Journal ◽

10.1042/bj20041144 ◽

2005 ◽

Vol 385 (2) ◽

pp. 527-535 ◽

Cited By ~ 84

Author(s):

Kalle KIPPER ◽

Priit VÄLJAMÄE ◽

Gunnar JOHANSSON

Keyword(s):

Bacterial Cellulose ◽

Trichoderma Reesei ◽

Anthranilic Acid ◽

Degree Of Polymerization ◽

Cellulose Substrates ◽

Quantitative Monitoring ◽

End Groups ◽

Alternative Means ◽

Burst Kinetics ◽

Hydrolysis Of

Reaction conditions for the reducing-end-specific derivatization of cellulose substrates with the fluorogenic compound, anthranilic acid, have been established. Hydrolysis of fluorescence-labelled celluloses by cellobiohydrolase Cel7A from Trichoderma reesei was consistent with the active-site titration kinetics (burst kinetics), which allowed the quantification of the processivity of the enzyme. The processivity values of 88±10, 42±10 and 34±2.0 cellobiose units were found for Cel7A acting on labelled bacterial cellulose, bacterial microcrystalline cellulose and endoglucanase-pretreated bacterial cellulose respectively. The anthranilic acid derivatization also provides an alternative means for estimating the average degree of polymerization of cellulose and, furthermore, allows the quantitative monitoring of the production of reducing end groups on solid cellulose on hydrolysis by cellulases. Hydrolysis of bacterial cellulose by cellulases from T. reesei revealed that, by contrast with endoglucanase Cel5A, neither cellobiohydrolases Cel7A nor Cel6A produced detectable amounts of new reducing end groups on residual cellulose.

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Purification and properties of three (1→3)-β-d-glucanase isoenzymes from young leaves of barley (Hordeum vulgare)

Biochemical Journal ◽

10.1042/bj2890453 ◽

1993 ◽

Vol 289 (2) ◽

pp. 453-461 ◽

Cited By ~ 89

Author(s):

M Hrmova ◽

G B Fincher

Keyword(s):

Hordeum Vulgare ◽

Elevated Temperatures ◽

Gel Filtration ◽

Degree Of Polymerization ◽

Exchange Chromatography ◽

Purification And Properties ◽

Young Leaves ◽

Monomeric Proteins ◽

Ph Range ◽

Hydrolysis Of

Three (1->3)-beta-D-glucan glucanohydrolase (EC 3.2.1.39) isoenzymes GI, GII and GIII were purified from young leaves of barley (Hordeum vulgare) using (NH4)2SO4 fractional precipitation, ion-exchange chromatography, chromatofocusing and gel-filtration chromatography. The three (1->3)-beta-D-glucanases are monomeric proteins of apparent M(r)32,000 with pI values in the range 8.8-10.3. N-terminal amino-acid-sequence analyses confirmed that the three isoenzymes represent the products of separate genes. Isoenzymes GI and GII are less stable at elevated temperatures and are active over a narrower pH range than is isoenzyme GIII, which is a glycoprotein containing 20-30 mol of hexose equivalents/mol of enzyme. The preferred substrate for the enzymes is laminarin from the brown alga Laminaria digitata, an essentially linear (1->3)-beta-D-glucan with a low degree of glucosyl substitution at 0-6 and a degree of polymerization of approx. 25. The three enzymes are classified as endohydrolases, because they yield (1->3)-beta-D-oligoglucosides with degrees of polymerization of 3-8 in the initial stages of hydrolysis of laminarin. Kinetic analyses indicate apparent Km values in the range 172-208 microM, kcat. constants of 36-155 s-1 and pH optima of 4.8. Substrate specificity studies show that the three isoenzymes hydrolyse substituted (1->3)-beta-D-glucans with degrees of polymerization of 25-31 and various high-M(r), substituted and side-branched fungal (1->3;1->6)-beta-D-glucans. However, the isoenzymes differ in their rates of hydrolysis of a (1->3;1->6)-beta-D-glucan from baker's yeast and their specific activities against laminarin vary significantly. The enzymes do not hydrolyse (1->3;1->4)-beta-D-glucans, (1->6)-beta-D-glucan, CM-cellulose, insoluble (1->3)-beta-D-glucans or aryl beta-D-glycosides.

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Polymerization of n-butyl methylacrylate using bis(β- ketoamino)nickel(II)/MAO catalytic systems

e-Polymers ◽

10.1515/epoly.2008.8.1.967 ◽

2008 ◽

Vol 8 (1) ◽

Author(s):

Xiaohui He ◽

Yiwang Chen ◽

Yongming Liu ◽

Muqing Chen ◽

Shuxian Yu ◽

...

Keyword(s):

Molecular Weight ◽

Monomer Concentration ◽

Polymerization Temperature ◽

Moderate Activity ◽

Polymerization Time ◽

Catalytic Systems ◽

Molecular Weights ◽

Molar Ratios ◽

Broad Molecular Weight Distribution ◽

C Nmr

AbstractThe polymerizations of n-butyl methylacrylate (nBMA) were carried out using bis(β-ketoamino)nickel(II) complexes (Ni[CH3C(O)CHC(NR)CH3]2: R = phenyl, 1; R = naphthyl, 2) in combination with methylaluminoxane (MAO) in toluene. The effect of parameters such as polymerization temperature, Al/Ni molar ratios, polymerization time, and monomer concentration, on catalytic polymerization activity and polymer molecular weights, were examined in detail. Both of the nickel(II) catalytic systems exhibited moderate activity, and produced P(nBMA) with high molecular weight and relatively broad molecular weight distribution (Mw/Mn=2.0~3.0. The obtained polymer has been characterized by means of FTIR, 1H NMR, 13C NMR, DSC, and WAXD technique and was confirmed to be syndio-rich stereospecific P(nBMA).

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STRUCTURE OF A GALACTURONAN FROM SUNFLOWER PECTIC ACID

Canadian Journal of Chemistry ◽

10.1139/v66-190 ◽

1966 ◽

Vol 44 (11) ◽

pp. 1275-1282 ◽

Cited By ~ 34

Author(s):

V. Zitko ◽

C. T. Bishop

Keyword(s):

Galacturonic Acid ◽

Periodate Oxidation ◽

Degree Of Polymerization ◽

Critical Assessment ◽

Molar Ratio ◽

Aqueous Methanol ◽

Pectic Acid ◽

Potassium Borohydride ◽

Rate Of Hydrolysis ◽

Hydrolysis Of

Fractions of sunflower pectic acid containing 89.8%, 94.2%, and 91.4% of D-galacturonic acid were carboxyl reduced as their methyl or ethylene glycol esters by potassium borohydride. Critical assessment of the effects of three different solvents (water, 80% aqueous dimethyl sulfoxide, and 80% aqueous methanol) on the efficiency of reduction showed that the latter solvent was best. The reductions caused a decrease in the degree of polymerization from 270 to 21. Measurement of the rates of hydrolysis of partially reduced pectic acids containing 90%, 41.6%, 19.9%, 11.0%, and 0.65% of D-galacturonic acid showed that the rate of hydrolysis was directly related to the proportion of galacturonosidic linkages present. Methylation and hydrolysis of the carboxyl-reduced pectic acid fractions yielded 2,3,4,6-tetra-O-methyl-D-galactose and 2,3,6-tri-O-methyl-D-galactose in an approximate molar ratio of 1:20. Results of the periodate oxidation of the carboxyl-reduced pectic acid supported the conclusion inferred from the methylation results that the pectic acid was a linear polymer of 1 → 4 linked α-D-galacturonic acid units.

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