•PVA/CNCs composites were prepared by solution casting technique.•The composites were characterized by methods of FTIR, XRD, DSC and TGA.•Thermal stability of the PVA/CNCs composites was studied.•The ...composites exhibit a significantly improved thermal resistance.•The thermal stability is maximally enhanced at a certain PVA/CNCs ratio.
Thermal stability of polyvinyl alcohol/cellulose nanocrystals (PVA/CNCs) composites prepared with solution casting technique was studied. The PVA/CNCs composites were characterized by Fourier transform infrared spectrometry, X-ray diffraction, differential scanning calorimeter (DSC) and thermogravimetric (TG) analysis. Due to the presence of CNCs nanoparticles, thermal degradation of the composites occurs at much higher temperatures compared to that of the neat PVA. Thermal stability of the PVA/CNCs composites is maximally enhanced with CNCs content of 8–12 wt%. Some thermal degradation products of the PVA/CNCs composites were identified by mass spectrometric analysis. TG measurements with synchronous recording of mass spectra revealed that the thermal degradation of both CNCs and PVA in the composites with CNCs content of 8–12 wt% occurs simultaneously at a much higher temperature than that of CNCs or the neat PVA. However, with increasing CNCs content more than 12 wt% the thermal stability of the composites decreases. In this case, the degradation of CNCs comes first followed by the degradation of PVA.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
•PEO/CNCs composites were prepared by solution casting technique.•The composites were characterized by SEM, FTIR, XRD, DSC, TGA, tensile testing.•Morphology, crystalline structure, and reinforcing ...effect have been studied.•Some composites properties are extreme at a certain PEO/CNCs ratio.
Composite films of polyethylene oxide/cellulose nanocrystals (PEO/CNCs) comprising up to 75wt.% CNCs were obtained via solution casting. For the first time, investigations of the PEO/CNCs composite films over a wide composition range were carried out. Morphology, crystalline structure, thermal stability and the resulting reinforcing effect on the PEO matrix were studied. Polarizing optical microscopy (POM), scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric (TG) analysis, Fourier transform infrared spectroscopy (FTIR), and tensile testing were used to examine the properties of the composites. The revealed extreme dependences of the composite properties refer to the CNCs content of 15–35wt.%. This composition range is characterized by destruction of PEO spherulites and appearance of a pronounced PEO fibrillar structure.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
In this work, we have developed methods of synthesis of cellulose nanocrystal (CNC) conjugates with chlorotriazine reactive dyes (RDs)—reactive violet, reactive-bright red and reactive ...bright-orange.) The prepared CNC-RD conjugates were characterized by a complex of techniques: UV–Vis, FTIR and solid-state
13
C NMR spectroscopy, thermogravimetric and elemental analysis, particle size and zeta potential analysis, scanning electron and polarization optical microscopy. An analysis of the solid state
13
C NMR spectra allowed us to conclude that the crystallinity index of the CNC-RD conjugates, compared to CNCs, did not change, i.e. RDs covalently bonded with the surface of the CNC particles and did not affect the CNC crystalline structure. The amount of the dye covalently bonded to the CNC particle surface was determined based on the elemental analysis data and using a square-cross-section model of the cellulose nanocrystal. The results obtained enabled us to make a conclusion that the RD covalent fixation was selective and occurred on one of the CNC ends (the so-called reducing end of the cellulose polymeric chain). Successful modification of the CNC surface was confirmed by UV–Vis spectroscopy. It was found that aqueous suspensions of the CNC-reactive violet dye conjugates possessed indicator properties. The size and charges of the CNC-RD particles in diluted aqueous suspensions were determined; the CNC-RD aqueous suspensions were found to have high colloidal stability. The stabilizing effect of the CNC-reactive violet dye conjugate for the formation of Pickering emulsions of the oil-in-water type was studied. It was shown that the CNC-reactive violet dye conjugate effectively stabilized
n
-decane emulsions in water.
Graphic abstract
Full text
Available for:
EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
In this work, a series of polyacrylamide/cellulose nanocrystal (PAM/CNC) composites with a wide range of compositions were prepared by a solution casting method. Subsequently, the influence of the ...PAM conformation on the behaviour of the PAM/CNC composites was studied. The microstructural, thermal, and mechanical properties of the PAM/CNC composites were also investigated, as well as their flocculation and dispersion behaviour. Thermal degradation of both CNC and PAM in the composites occurred simultaneously, at a much higher temperature than the degradation of the neat CNC. By TEM and SEM, PAM globule aggregates in the PAM/CNC composites were detected. With an increase in the medium acidity, the PAM globule aggregate size of in the composites decreased. Moreover, the composite films cast from high pH solutions (extended PAM conformation) exhibited superior strength properties than those cast from low pH solutions (contracted coil PAM conformation). The PAM globule conformation provided good re-dispersibility of the freeze-dried PAM/CNC composites by preventing aggregation of the CNC particles. The PAM globule adsorption onto the CNC particles caused CNC surface hydrophobization and a decrease in their surface charge, while maintaining high colloidal stability of the CNC suspensions. Furthermore, the CNC particles with adsorbed PAM were demonstrated to be useful as emulsifiers and compatibilisers.
Materials Science; Nanotechnology; Cellulose nanocrystals; Polyacrylamide; Polymer composites; Structure-property relationships.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In this work, we have applied, for the first time, solution plasma processing of cellulose-containing material to produce cellulose nanocrystals (CNC). The CNC samples produced in three different ...modes of solution plasma treatment were characterized using methods of dynamic light scattering, infrared spectroscopy, transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The proposed method of CNC production comprising the oxidation–hydrolysis strategy has proved to be effective and allowed us to reduce significantly the time of acid hydrolysis and to increase considerably the total CNC yield.
Graphical Abstract
Full text
Available for:
EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The data on the synthesis of functional materials based on nanocrystalline cellulose (NCC) published over the past 10 years are analyzed. The liquid-crystal properties of NCC suspensions, methods of ...investigation of NCC suspensions and films, conditions for preserving chiral nematic structure in the NCC films after removal of the solvent and features of templated sol - gel synthesis of functional materials based on NCC are considered. The bibliography includes 106 references.
The properties of two cellulose samples obtained by separation from water dispersion of whiskers by the two different methods, namely freeze-drying and water evaporation, have been investigated. The ...way cellulose is separated has been shown to have an effect on the properties of the material produced.
► The properties of two cellulose samples obtained by different methods are studied. ► The nanocellulose dispersions were dried by freeze-drying and water evaporation. ► The way cellulose dispersion is dried has an effect on the properties of the material. ► The nanocellulose samples display different crystallinities and thermal degradations.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
•Surface modification of CNCs was carried out by physical adsorption of PVP.•A solution of PVP-modified CNCs in CH2Cl2 was used to prepare a composite with PCL.•Physicochemical properties of ...CNC/PVP/PCL composites were studied.•MD simulations of the interactions between the system components were carried out.
In this paper, physical adsorption of polyvinylpyrrolidone (PVP) was used as the method of surface modification of cellulose nanocrystals (CNCs). The work also considers the PVP molecular weight effect on dispersion of the surface-modified CNC in dichloromethane (DCM). The authors analyze the physicochemical properties of the composite with polycaprolactone (PCL) - CNC/PVP/PCL - prepared from a solution of PVP-modified CNCs in DCM, and conduct a molecular dynamics simulation of the interactions between the system (CNC, PVP, PCL) components in vacuum and in a solvent medium (water, DCM). According to the simulation results, the CNC/PVP/PCL composite has the following structure: PCL macromolecules have practically no direct contacts with the CNC surface but are located between the PVP macromolecules that, in their turn, are predominantly located near the CNC particle surface.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
10.
SYNTHESIS AND PROPERTIES OF NANOCELLULOSE-DYE CONJUGATES Surov, Oleg V.; Voronova, Marina I.; Rubleva, Natalia V. ...
IZVESTIYA VYSSHIKH UCHEBNYKH ZAVEDENII KHIMIYA KHIMICHESKAYA TEKHNOLOGIYA,
02/2021, Volume:
64, Issue:
2
Journal Article
Peer reviewed
Open access
Synthesis of conjugates of cellulose nanocrystals (CNC) with chlortriazine reactive dyes (RD) has been developed. The obtained CNC-RD conjugates were characterized using a complex of modern methods: ...UV-Vis, IR and 13C solid state NMR spectroscopy, thermogravimetric and elemental analysis, particle size and zeta potential analysis, scanning electron and polarization optical microscopy. IR spectra of CNC-RD films show absorption bands typical of cellulose. The formation of a covalent cellulose-dye bond is confirmed by the presence of characteristic absorption bands of the resulting ether bond in the region of 1000-1300 cm-1. Based on the analysis of solid-state 13C NMR spectra, it was concluded that the degree of crystallinity of the CNC-RD conjugates does not change compared to the CNC, i.e. the RD covalently bind to the surface of the CNC particles and do not affect the crystal structure of the CNC. Using a simple model of CNC with square cross-section, and based on the elemental analysis data, the amount of covalently bound dye on the surface of CNC particles was estimated. The results obtained allow us to conclude that covalent bound of RD occurs selectively at one of the ends of the cellulose nanocrystal (the so-called reducing end of the cellulose polymer chain). Successful CNC surface modification is confirmed by UV-Vis spectroscopy. It was found that aqueous suspensions of CNC-RD conjugates have indicator properties. The sizes and charges of the particles of CNC-RD conjugates in dilute aqueous suspensions were determined. High colloidal stability of the CNC-RD aqueous suspensions was confirmed. It has been shown that CNC-RD colloidal suspensions possess liquid crystalline properties, which is clearly demonstrated by their iridescent color in polarized light with stirring. CNC films modified with RD also possess birefringence properties and exhibit an iridescent color in polarized light. The morphology of CNC-RD particles was studied using scanning electron microscopy. The thermal stability of the CNC-RD conjugates was studied.
PDF
