PREPARATION OF CHITOSAN GRAFT COPOLYMERS AND STUDY OF THEIR WATER-SWELLING PROPERTIES

In this work, graft copolymers of chitosan with trimethylmethacryloxyethylammonium methyl sulfate were synthesized by the method of controlled radical polymerization, and it was found that replacing the dimethylformamide aprotic solvent with water increases the degree of grafting. With the aim of the possible use of chitosan copolymers as a functional component for regulating the water-swelling properties of elastomers, the kinetics of swelling of the samples was investigated. An increase in the degree of swelling of the copolymers in comparison with the initial chitosan was revealed, and the influence of the molecular weight and the conditions of their synthesis was established.

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Effect of Oxidation of Rubber on the Kinetics of Its Swelling

Rubber Chemistry and Technology ◽

10.5254/1.3542503 ◽

1956 ◽

Vol 29 (1) ◽

pp. 135-144 ◽

Cited By ~ 2

Author(s):

V. E. Gul ◽

I. V. Khodzhaeva ◽

B. A. Dogadkin

Keyword(s):

Molecular Weight ◽

Structural Properties ◽

Polar Solvent ◽

Kinetic Curve ◽

Linear Segment ◽

Oxidation Processes ◽

Degree Of Dispersion ◽

Degree Of Swelling ◽

Kinetics Of ◽

Oxidation Effect

Abstract 1. Swelling of rubber during reaction with oxygen is described by a kinetic curve. After a sharply rising segment, corresponding to the diffusion of the solvent, the curve has a practically linear segment, reflecting a slow change of the degree of swelling due to the oxidation processes which accompany swelling. 2. The swelling maximum of rubber in a polar solvent when the oxidation effect is disregarded, corresponds to the molecular weight, degree of dispersion, and other structural properties of the rubber. The slope of the linear segment of the kinetic curve of swelling can serve as a characteristic of the resistance of the rubber to oxidation.

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Study of Sorption Kinetics of Doxycycline on pH Sensitive Hydrogel-based Graft Copolymers of Chitosan/Arabinogalactan/ Gummiarabic with Vinyl Monomers

Oriental Journal Of Chemistry ◽

10.13005/ojc/370612 ◽

2021 ◽

Vol 37 (6) ◽

pp. 1350-1358

Author(s):

Mirvari Khalig Hasanova

Keyword(s):

Electrostatic Interactions ◽

Graft Copolymers ◽

Sorption Kinetics ◽

Ph Sensitive ◽

Vinyl Monomers ◽

Sorption Mechanism ◽

Volume Absorption ◽

Water Swelling ◽

Kinetics And Isotherms ◽

Kinetics Of

Graft copolymers of natural polysaccharides chitosan (Chs), gummi-arabic (GA) and arabinogalactan (AG) were synthesized with N-vinylpyrrolidone (VPr) (4-vinylpyridine and N-vinylpyrrolidone used as comonomers for chitosan grafting), and then pH-sensitive hydrogels were designing by cross-linked them with N,N-methylene-bis-acrylamide. Effective sorption of doxycycline from aqueous solutions with water-swelling gels has been studied experimentally. The effect of gel dose, initial concentration of doxycycline, pH medium and solution ionic strength of the sorption rate and capacity of the antibiotic was systematically studied. The surface and volume absorption kinetics and isotherms of the process have also been investigated. It was found that the max sorption capacity for swellable gels varies between Chs-graft-VPr/4VPAG/graft-VPrGA/graft-VPr. It has been shown that the sorption mechanism is mainly dominated by physical sorption and to some extent hydrogen bonds and electrostatic interactions.

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Thermal Degradation Kinetics and Modeling Study of Ultra High Molecular Weight Polyethylene (UHMWP)/Graphene Nanocomposite

Molecules ◽

10.3390/molecules26061597 ◽

2021 ◽

Vol 26 (6) ◽

pp. 1597

Author(s):

Iman Jafari ◽

Mohamadreza Shakiba ◽

Fatemeh Khosravi ◽

Seeram Ramakrishna ◽

Ehsan Abasi ◽

...

Keyword(s):

Thermal Stability ◽

Molecular Weight ◽

Thermal Degradation ◽

High Molecular Weight ◽

Degradation Kinetics ◽

Graphene Nanosheets ◽

Thermal Degradation Kinetics ◽

Graphene Nanocomposites ◽

Kinetics Of ◽

Ultra High Molecular Weight

The incorporation of nanofillers such as graphene into polymers has shown significant improvements in mechanical characteristics, thermal stability, and conductivity of resulting polymeric nanocomposites. To this aim, the influence of incorporation of graphene nanosheets into ultra-high molecular weight polyethylene (UHMWPE) on the thermal behavior and degradation kinetics of UHMWPE/graphene nanocomposites was investigated. Scanning electron microscopy (SEM) analysis revealed that graphene nanosheets were uniformly spread throughout the UHMWPE’s molecular chains. X-Ray Diffraction (XRD) data posited that the morphology of dispersed graphene sheets in UHMWPE was exfoliated. Non-isothermal differential scanning calorimetry (DSC) studies identified a more pronounced increase in melting temperatures and latent heat of fusions in nanocomposites compared to UHMWPE at lower concentrations of graphene. Thermogravimetric analysis (TGA) and derivative thermogravimetric (DTG) revealed that UHMWPE’s thermal stability has been improved via incorporating graphene nanosheets. Further, degradation kinetics of neat polymer and nanocomposites have been modeled using equations such as Friedman, Ozawa–Flynn–Wall (OFW), Kissinger, and Augis and Bennett’s. The "Model-Fitting Method” showed that the auto-catalytic nth-order mechanism provided a highly consistent and appropriate fit to describe the degradation mechanism of UHMWPE and its graphene nanocomposites. In addition, the calculated activation energy (Ea) of thermal degradation was enhanced by an increase in graphene concentration up to 2.1 wt.%, followed by a decrease in higher graphene content.

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Isothermal Crystallization Kinetics of Poly(ethylene oxide)/Poly(ethylene glycol)-g-silica Nanocomposites

Polymers ◽

10.3390/polym13040648 ◽

2021 ◽

Vol 13 (4) ◽

pp. 648

Author(s):

Xiangning Wen ◽

Yunlan Su ◽

Shaofan Li ◽

Weilong Ju ◽

Dujin Wang

Keyword(s):

Molecular Weight ◽

Ethylene Oxide ◽

Crystallization Kinetics ◽

Isothermal Crystallization ◽

Crystallization Rate ◽

Poly Ethylene Glycol ◽

Isothermal Crystallization Kinetics ◽

Poly Ethylene Oxide ◽

Poly Ethylene ◽

Kinetics Of

In this work, the crystallization kinetics of poly(ethylene oxide) (PEO) matrix included with poly(ethylene glycol) (PEG) grafted silica (PEG-g-SiO2) nanoparticles and bare SiO2 were systematically investigated by differential scanning calorimetry (DSC) and polarized light optical microscopy (PLOM) method. PEG-g-SiO2 can significantly increase the crystallinity and crystallization temperature of PEO matrix under the non-isothermal crystallization process. Pronounced effects of PEG-g-SiO2 on the crystalline morphology and crystallization rate of PEO were further characterized by employing spherulitic morphological observation and isothermal crystallization kinetics analysis. In contrast to the bare SiO2, PEG-g-SiO2 can be well dispersed in PEO matrix at low P/N (P: Molecular weight of matrix chains, N: Molecular weight of grafted chains), which is a key factor to enhance the primary nucleation rate. In particular, we found that the addition of PEG-g-SiO2 slows the spherulitic growth fronts compared to the neat PEO. It is speculated that the interfacial structure of the grafted PEG plays a key role in the formation of nuclei sites, thus ultimately determines the crystallization behavior of PEO PNCs and enhances the overall crystallization rate of the PEO nanocomposites.

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