Effect of chemical structure and molecular weight on the properties of lignin-based ultrafine carbon fibers

An alkali lignin (OL) with a weight-average molecular weight (Mw) of 11646 g/mol was used to prepare low-molecular weight lignin for resin synthesis. The low-molecular weight lignin feedstock was obtained via base-catalysed depolymerisation (BCD) treatments at different combined severity factors. Sequential fractionation of the OL and BCD-treated lignins using organic solvents with different Hildebrand solubility parameters were used to alter the homogeneity of the OL. The yield and properties of OL itself and OL and BCD-treated OL dissolved in propan-1-ol (F1), ethanol (F2), and methanol (F3) were determined. Regardless of the treatment applied, a small amount of OL was dissolved in F1 and F2. The BCD treatment did not increase the yield of F1 but did increase the yields of F2 and F3. Gel permeation chromatography (GPC) showed that the repolymerization reaction occurred in F3 for all BCD-treated OL, so these lignins were not suitable for use as feedstocks for resin production. The GPC, 13Carbon-nuclear magnetic resonance, and Fourier transform infrared spectroscopy analyses confirmed that the F3 in OL exhibited the optimum yield, molecular weight distribution, and chemical structure suitable for use as feedstocks for resin synthesis.

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Kraft lignin-based piezoresistive sensors: Effect of chemical structure on the microstructure of ultrathin carbon fibers

International Journal of Biological Macromolecules ◽

10.1016/j.ijbiomac.2020.02.225 ◽

2020 ◽

Vol 151 ◽

pp. 730-739 ◽

Cited By ~ 1

Author(s):

Shichao Wang ◽

Mugaanire Tendo Innocent ◽

Qianqian Wang ◽

Hengxue Xiang ◽

Jianguo Tang ◽

...

Keyword(s):

Carbon Fibers ◽

Chemical Structure ◽

Kraft Lignin ◽

Piezoresistive Sensors

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Chemical Depolymerisation of Natural Rubber in Biphasic Medium

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1024.193 ◽

2014 ◽

Vol 1024 ◽

pp. 193-196

Author(s):

Ibrahim Suhawati ◽

Asrul Mustafa

Keyword(s):

Molecular Weight ◽

Natural Rubber ◽

Chemical Structure ◽

Inner Core ◽

Particle Surface ◽

Natural Rubber Latex ◽

Carbonyl Groups ◽

Latex Particles ◽

Liquid Natural Rubber ◽

Biphasic Medium

The molecular weight of natural rubber (NR) can be reduced via depolymerization reaction to produce liquid natural rubber (LNR) with a molecular weight less than 50 000 g/mol. In the reaction, hydrogen peroxide and sodium nitrite were added to natural rubber latex to initiate a redox type reaction which then breaks the NR chain. Low permeation of reagents into latex particles allows the degradation to occur greater at the latex particle surface relative to the inner core contributes to high molecular weight distribution (MWD) or polydispersity of the LNR obtained. In this recent works, the reaction was carried out in a biphasic medium consisting of water and toluene phases. Toluene swells latex particles as indicated by the SEM micrographs showing changes in the size of latex particles. This occurrence is suggested to increase the influx of reagents into the latex particles. Consequently, with higher permeation of reagents into the latex particles resulted in the decrease of molecular weight and lower polydispersity of the LNR obtained. Chemical structure analysize showed that the LNRs obtained were attached with hydroxyl and carbonyl groups.

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The Most Important Methods for Depollution of Hydrocarbons Polluted Soils

Bulletin of University of Agricultural Sciences and Veterinary Medicine Cluj-Napoca Agriculture ◽

10.15835/buasvmcn-agr:3734 ◽

1970 ◽

Vol 66 (1) ◽

Author(s):

Laura DOBOS ◽

Carmen PUIA

Keyword(s):

Molecular Weight ◽

Polycyclic Aromatic Hydrocarbons ◽

Aromatic Hydrocarbons ◽

Heterocyclic Compounds ◽

Chemical Structure ◽

Complex Mixture ◽

Naphthenic Acids ◽

International Agency ◽

Polluted Soils ◽

Polycyclic Aromatic

Crude oil is a highly complex mixture of hydrocarbons amounting to hundreds of individual compounds with different chemical structure and molecular weight plus a series of lower molecular weight compounds other than hydrocarbons (phenols, thiols, naphthenic acids, heterocyclic compounds with N (pyridines, pyrrole, indole, s.o.) compounds S (alkyl thiols, thiophene, etc.) (Zarnea, 1994). Mineral oil and polycyclic aromatic hydrocarbons (PAHs) creates larger environmental problems. They are considered particularly dangerous. In this regard, EPA Agency from U.S.A. includes a number of polycyclic aromatic hydrocarbons under 16 priority pollutants, which require special attention. IARC (International Agency for Research on Cancer) has identified 15 types of polycyclic aromatic hydrocarbons including six of the 16 types of PAHs, identifiable by the USEPA as having carcinogenic properties (Chauhan Archana et al., 2008).

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Molecular Structure and Macroscopic Properties of Synthetic Cis-Poly(Isoprene)

Rubber Chemistry and Technology ◽

10.5254/1.3540444 ◽

1974 ◽

Vol 47 (2) ◽

pp. 342-356 ◽

Cited By ~ 8

Author(s):

V. A. Grechanovskii ◽

I. Ya Poddubnyi ◽

L. S. Ivanova

Keyword(s):

Molecular Weight ◽

Functional Groups ◽

Chemical Structure ◽

Sol Gel ◽

Average Molecular Weight ◽

Dense Network ◽

Green Strength ◽

Gel Fraction ◽

Rubber Compounds ◽

Processing Properties

Abstract By changing the sol-gel ratio and the structure of the gel fraction it is possible to obtain various grades of synthetic cis-poly(isoprene) which show promise for different applications in the tire and mechanical rubber goods industries. The processability of commercial SKI-3 rubber (at a given average molecular weight of sol) depends mainly on the structure of the gel fraction. Thus, for example, inferior processing properties of rubber compounds is associated primarily with the presence of tight gel. The content and structure of the gel fraction also significantly affect plasto-elastic properties of raw rubbers, e.g. a low plasticity of raw rubbers owes to the increased content of gel fraction. The reduced green strength of compounds based on SKI—3 rubber is accounted for by its chemical structure. Conventional methods used to change the properties of rubbers (including the variation in molecular weight, molecular weight distribution, branching degree, and variation in the content and structure of gel fraction) cannot be considered to be adequate to tackle the problem of the green strength of SKI—3 black stocks. The way to solve the problem appears to be the introduction of functional groups into the polymer chain at the stage of synthesis or processing. These functional groups should be active as to the formation of labile rubber—carbon black—rubber and/or rubber—rubber bonds. High purity of microstructure is necessary but not sufficient for obtaining the required level of green strength of compounded SKI—3. The gel fractions of SKI—3 rubber yield vulcanizates with a more dense network than the corresponding sol vulcanizates. The temperature dependence of the tensile strength is controlled by the network density of vulcanizates from high cis-1,4 poly(isoprene).

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Neuroprotective Metabolites from Vietnamese Marine Derived Fungi of Aspergillus and Penicillium Genera

Marine Drugs ◽

10.3390/md18120608 ◽

2020 ◽

Vol 18 (12) ◽

pp. 608

Author(s):

Elena V. Girich ◽

Anton N. Yurchenko ◽

Olga F. Smetanina ◽

Phan Thi Hoai Trinh ◽

Ngo Thi Duy Ngoc ◽

...

Keyword(s):

Molecular Weight ◽

Secondary Metabolites ◽

Cell Viability ◽

Chemical Structure ◽

Aspergillus Terreus ◽

Marine Fungi ◽

2D Nmr ◽

Natural Source ◽

Low Molecular Weight ◽

First Time

Low molecular weight secondary metabolites of marine fungi Aspergillus flocculosus, Aspergillus terreus and Penicillium sp. from Van Phong and Nha Trang Bays (Vietnam) were studied and a number of polyketides, bis-indole quinones and terpenoids were isolated. The structures of the isolated compounds were determined by 1D and 2D NMR and HR-ESI-MS techniques. Stereochemistry of some compounds was established based on ECD data. A chemical structure of asterriquinone F (6) was thoroughly described for the first time. Anthraquinone (13) was firstly obtained from a natural source. Neuroprotective influences of the isolated compounds against 6-OHDA, paraquat and rotenone toxicity were investigated. 4-Hydroxyscytalone (1), 4-hydroxy-6-dehydroxyscytalone (2) and demethylcitreoviranol (3) have shown significant increasing of paraquat- and rotenone-treated Neuro-2a cell viability and anti-ROS activity.

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Predicting skin permeation rate from nuclear magnetic resonance spectra

Green Chemistry ◽

10.1039/c6gc00945j ◽

2016 ◽

Vol 18 (16) ◽

pp. 4468-4474 ◽

Cited By ~ 1

Author(s):

Nan An ◽

John-Hanson Machado ◽

Yuechuan Tang ◽

Jakub Kostal ◽

Adelina Voutchkova-Kostal

Keyword(s):

Molecular Weight ◽

Nuclear Magnetic Resonance ◽

Magnetic Resonance ◽

Spectroscopic Data ◽

Chemical Structure ◽

Skin Permeation ◽

Permeation Rate ◽

Organic Chemicals ◽

Predictive Method ◽

Nuclear Magnetic Resonance Spectra

A predictive method is reported for estimating skin permeation of organic chemicals exclusively from NMR spectroscopic data and molecular weight, which does not require knowledge of chemical structure.

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Effect of molecular weight and chemical structure on thermal and rheological properties of gelling κ/ι-hybrid carrageenan solutions

Carbohydrate Polymers ◽

10.1016/j.carbpol.2011.03.006 ◽

2011 ◽

Vol 85 (2) ◽

pp. 429-438 ◽

Cited By ~ 31

Author(s):

Hiléia K.S. Souza ◽

Loic Hilliou ◽

Margarida Bastos ◽

Maria Pilar Gonçalves

Keyword(s):

Molecular Weight ◽

Rheological Properties ◽

Chemical Structure

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The Structure of Angular Polycycloisoprene

Rubber Chemistry and Technology ◽

10.5254/1.3539586 ◽

1963 ◽

Vol 36 (2) ◽

pp. 558-560 ◽

Cited By ~ 2

Author(s):

F. T. Wallenberger

Keyword(s):

Molecular Weight ◽

Refractive Index ◽

Chemical Structure ◽

Polymer Melt ◽

Stannic Chloride ◽

Polymeric Product ◽

Melt Temperature ◽

Reaction Proceeds ◽

Ring Polymers ◽

Silent Electric Discharge

Abstract Lewis and Brö nsted acids, heat, silent electric discharge and cathode rays cause progressing isomerization of synthetic and natural cis-1,4-polyisoprene to yield a polymeric product which has the empirical formula, (C5H8)n identical with that of the initial rubber hydrocarbon. The reaction, commonly carried out in benzene with stannic chloride as catalyst, is accompanied by an increase in specific gravity, refractive index and polymer melt temperature and a decrease in unsaturation, intrinsic viscosity and molecular weight of the material. The resulting polymer, readily soluble in a variety of solvents, is known as cyclized rubber, cyclo-caoutchouc, or “Pliolite-NR”, manufactured by the Goodyear Tire and Rubber Company. Staudinger recognized as early as 1926 that the reaction proceeds by isomerization and intramolecular cyclization. D'lanni postulated formation of cyclohexane rings within the polymer chain, while Veersen extended D'lanni's proposal and suggested random protonation of bonds leading to intralinear, mono-, di-, and polycyclic ring polymers. Ideally, complete and stereoselective cyclization would lead to angular polycycloisoprene. Comprehensive reviews concerning the chemistry of the cyclization have been published by Reese and by Bloomfield. This communication provides the first chemical structure proof of the cyclized product. It is based on the cyclization of cis-1,4- and of trans-1,4-polyisoprene. The resulting products were identical and their properties in agreement with literature data. Hence cyclization must have proceeded through a common intermediate.

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