scholarly journals Adjustment of Hydrophobic Properties of Cellulose Materials

Polymers ◽  
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.

THE SYNTHESIS AND PROPERTIES OF ADENOSINE-2′ DIPHOSPHATE AND ADENOSINE-3′ DIPHOSPHATE

1967 ◽  
Vol 45 (1) ◽  
pp. 89-99 ◽  
Author(s):  
R. E. J. Mitchel ◽  
D. C. Ward ◽  
G. M. Tener
Keyword(s):  
Trichloroacetic Acid ◽  
Deae Cellulose ◽  
Side Reaction ◽  
Ion Exchange Chromatography ◽  
Exchange Chromatography ◽  
Hydroxyl Groups ◽  
Chemical Methods ◽  
Cyclic Phosphate ◽  
Hydrolysis Of ◽  
Direct Hydrolysis

Adenosine-2′ diphosphate (A2'DP) and adenosine-3′ diphosphate (A3′DP) have been prepared by reaction between the corresponding mononucleotides with phosphoramidic acid in formamide. The products were isolated by ion-exchange chromatography on DEAE-cellulose and characterized by enzymic and chemical methods. A major side reaction in the synthesis is the phosphorylation of unprotected hydroxyl groups oil the nucleotides. A2′DP and A3′DP were found to be more labile than adenosine-5′ diphosphate, and to decompose at neutral pH by direct hydrolysis of the pyrophosphate bond as well as by formation of adenosine-2′,3′ cyclic phosphate. They are stable in 10% trichloroacetic acid at 0° for 10 minutes. Phosphomonoesterase degrades both to nucleosides by way of the corresponding nucleoside monophosphates. Ribonuclease T2does not attack A2′DP but degrades A3′DP to adenosine-3′ phosphate. Neither nucleotide is degraded by snake venom or spleen phosphodiesterases under conditions where oligonucleotides are completely hydrolyzed.

Selective acid hydrolysis of 2,4,6-trimethylbenzyl esters and its application in peptide synthesis

1966 ◽  
Vol 19 (8) ◽  
pp. 1511 ◽  
Author(s):  
FHC Stewart
Keyword(s):  
Acid Hydrolysis ◽  
Peptide Synthesis ◽  
Trifluoroacetic Acid ◽  
Ester Group ◽  
Protecting Groups ◽  
Alkaline Conditions ◽  
Hydrolysis Of

Experiments with various N-acylamino acid 2,4,6-trimethylbenzyl esters have shown that the ester group is cleaved selectively by cold trifluoroacetic acid without affecting benzyloxycarbonyl, formyl, or phthaloyl amino-protecting groups present. The possible value of this selective behaviour in peptide syntheses where the use of alkaline conditions would be detrimental is illustrated by the synthesis of certain dipeptide derivatives.

scholarly journals Mussel-Inspired Co-Deposition of Polydopamine/Silica Nanoparticles onto Carbon Fiber for Improved Interfacial Strength and Hydrothermal Aging Resistance of Composites

Polymers ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 712 ◽  
Author(s):  
Xuejun Cui ◽  
Lichun Ma ◽  
Guangshun Wu
Keyword(s):  
Carbon Fibers ◽  
Interfacial Strength ◽  
Fiber Surface ◽  
The Novel ◽  
Hydrothermal Aging ◽  
One Pot ◽  
Polar Groups ◽  
Aging Resistance ◽  
Interfacial Compatibility ◽  
Hydrolysis Of

A novel and effective strategy was first proposed for the codeposition of a mussel-inspired nanohybrid coating with excellent wettability onto the surface of carbon fibers (CFs) by simultaneous polymerization of bioinspired dopamine (DA) and hydrolysis of commercial tetraethoxysilane (TEOS) in an eco-friendly one-pot process. Mussel-inspired nanohybrids could be adhered onto the surface of CFs firmly. The novel modification could afford sufficient polar groups and significantly improve fiber surface roughness and energy without decreasing fiber intrinsic strength, which were advantageous to promote interfacial compatibility and wettability between CFs and matrix resin. As a result, the interfacial shear strength of composites increased to 48.21 ± 1.45 MPa compared to that of untreated composites 29.47 ± 0.88 MPa. Meanwhile, the nanohybrid coating increased significantly composites’ hydrothermal aging resistance. The efficient strategy shows a promising and green platform of surface functionalization of CFs for preparing advanced polymer composites arising from broadly mechanical-demanding and energy-saving usages.

THE PROBLEM OF PLASTEIN FORMATION: II. THE CHEMICAL CHANGES INVOLVED IN PLASTEIN FORMATION BY PAPAIN AND BY PEPSIN

1940 ◽  
Vol 18b (9) ◽  
pp. 272-280 ◽  
Author(s):  
H. B. Collier
Keyword(s):  
Enzymatic Hydrolysis ◽  
Free Amino ◽  
Essential Role ◽  
Phenolic Hydroxyl ◽  
Carboxyl Groups ◽  
Hydroxyl Groups ◽  
Chemical Changes ◽  
Phenolic Hydroxyl Groups ◽  
Hydrolysis Of

It has been confirmed that free amino and carboxyl groups disappear during plastein formation from concentrated proteose by crystalline pepsin. Using papain, the changes are obscured by simultaneous hydrolysis. Enzymatic hydrolysis of the plasteins results in the liberation of free amino and carboxyl groups.Reactive "tyrosine" decreases during plastein formation by either enzyme. The same groups are liberated on enzymatic hydrolysis of the plasteins, in a manner analogous to that which takes place in the hydrolysis of typical proteins.It is concluded that in so far as the changes in amino, carboxyl, and "tyrosine" groups are concerned, the plasteins are similar to typical proteins. It is further suggested that the phenolic hydroxyl groups of tyrosine play an essential role in the structure of the protein molecule.Benzaldehyde was found to have no effect on the formation of plastein from proteose by crystalline pepsin.

scholarly journals New Diterpenes from Azorella spinosa

2014 ◽  
Vol 9 (1) ◽  
pp. 1934578X1400900 ◽  
Author(s):  
Luis Astudillo ◽  
Margarita Gutiérrez ◽  
Luisa Quesada ◽  
Aurelio San-Martín ◽  
Luis Espinoza ◽  
...  
Keyword(s):  
Ursolic Acid ◽  
Significant Activity ◽  
Chemical Methods ◽  
Enzymatic Assays ◽  
Aerial Parts ◽  
Basic Hydrolysis ◽  
Hydrolysis Of

Two new diterpenes,2-acetoxy-13-hydroxy-mulin-11-ene and 2-acetoxy-mulin-11, 13-diene, have been isolated from the aerial parts of Azorella spinosa and their structures determined by spectroscopic and conventional chemical methods. Furthermore, 2, 13-dihydroxy-mulin-11-ene was obtained using a basic hydrolysis of the first compound. Two diterpenes reported for other Azorella species have also been found, namely mulinolic acid and 13β-hydroxyazorellane, as well as the triterpene lactone of ursolic acid, quercetin, and 7-hydroxycoumarin. The compounds were evaluated using antibacterial, antioxidant and enzymatic assays; no significant activity was detected.

scholarly journals Comparative studies of the specificities of α-chymotrypsin and subtilisin BPN′. Studies with flexible and ‘locked’ substrates

1972 ◽  
Vol 126 (3) ◽  
pp. 659-665 ◽  
Author(s):  
T. N. Pattabiraman ◽  
W. B. Lawson
Keyword(s):  
Methyl Ester ◽  
Carbon Atom ◽  
Binding Site ◽  
Comparative Studies ◽  
Detrimental Effect ◽  
Optically Active ◽  
The Other ◽  
Optical Isomers ◽  
Polar Groups ◽  
Hydrolysis Of

Subtilisin BPN′ hydrolysed N-acetyl-l-3-(2-naphthyl)-alanine methyl ester, N-acetyl-l-leucine methyl ester and N-acetyl-l-valine methyl ester, faster than α-chymotrypsin. Of eight ‘locked’ substrates tested, only methyl 5,6-benzindan-2-carboxylate was hydrolysed faster by subtilisin, whereas the other esters were better substrates for chymotrypsin. Compared with the values for chymotrypsin, the stereospecific ratios during the hydrolysis of the optically active locked substrates by subtilisin were decreased by one and two orders of magnitude for bi- and tri-cyclic substrates respectively. The polar groups adjacent to the α-carbon atom of locked substrates did not contribute significantly to the reactivity of the more active optical isomers, but had a detrimental effect on the less active antipodes during hydrolysis by both the enzymes. These studies show that the binding site of subtilisin BPN′ is longer and broader than that of α-chymotrypsin.

Studies on the lignin of Eucalyptus regnans F. Muell. VII. The acid hydrolysis of ethanyol lignin-A

1953 ◽  
Vol 6 (2) ◽  
pp. 156 ◽  
Author(s):  
JWT Merewether
Keyword(s):  
Hydrochloric Acid ◽  
Acid Hydrolysis ◽  
Carbonyl Group ◽  
Dilute Hydrochloric Acid ◽  
Hydroxyl Groups ◽  
Eucalyptus Regnans ◽  
Ethoxyl Group ◽  
Hydrolysis Of

Ethanol lignin-A from the ethanolysis of Eucalyptus regnans P. Muell. has been hydrolysed with dilute hydrochloric acid with the object of ascertaining whether the combined ethoxyl is present as an acetal or as ether. Hydrolysis with 12 per cent. hydrochloric acid was found to split off one ethoxyl group, while hydrolysis with 20 per cent. acid brought about complete de-ethylation. The de-ethylated ethanol lignin-A contained one carbonyl group less and two hydroxyl groups more than the original ethanol lignin-A. These results lend no support to the hypothesis that alcohol lignins are acetals, and favour the theory that the combined alkoxyl is probably present as ether.

Preparation and Properties of Oxidized Coal/Polyaniline Composite Material

2011 ◽  
Vol 306-307 ◽  
pp. 220-223
Author(s):  
Xiao Ping Fan ◽  
An Ning Zhou
Keyword(s):  
Composite Material ◽  
In Situ Polymerization ◽  
Polymer Network ◽  
Interpenetrating Polymer Network ◽  
Hydroxyl Groups ◽  
Oxidized Coal ◽  
Pani Composite ◽  
Maximum Conductivity ◽  
Hydrolysis Of

Semi-interpenetrating polymer network of coal/polyaniline (PANI) composite material were prepared by in situ polymerization. Raw coal was oxidized in different conditions by H2O2 and HNO3, respectively. The total acidic groups analysis, Fourier transform infrared (FTIR) spectrum, and conductivity test of the raw coal and the oxidized coal/PANI composite material were conducted. The results showed that the increases of the carboxyl groups and the hydroxyl groups were mainly attributed to the hydrolysis of the weak ether link and the transform from the carboxylate to carboxylic acid. These increases were benefit to the reaction of coal and PANI, and consequently enhanced the conductivity of the composite material. The maximum conductivity of oxidized coal/PANI reached 4.72×10‑1 S/cm.

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