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Characteristics of physicochemical and rheological properties of chitosan hydrogels based on selected hydroxy acids

Zavyalova Olga, Gajewska Sandra, Dąbrowska-Wisłocka Dominika, Sionkowska Alina

Engineering of Biomaterials

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2021

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Vol. 24, no. 161

2--7

EN

Chitosan is a natural cationic polymer that dissolves in an acidic environment and forms gels. Its properties depend on the degree of deacetylation and molecular weight. It is a bioactive compound with antibacterial and film-forming properties that allow to increase the regenerative capacity of the skin. Moreover, it is biodegradable, biocompatible, non-toxic, and stable. In this research, chitosan was combined with mandelic and lactobionic acids which are characterized by biological activity and low toxicity. This combination not only has a positive effect on the chitosan solubility, but it also allows to obtain new biomaterials whose positive features of the base ingredients are enhanced by their synergistic effect. The obtained hydrogels were assessed regarding the interaction of chitosan and hydroxy acid molecules, and the stability of the resulting structures was examined. The research was performed by using rheological methods and IR spectroscopy. Chitosan hydrogels made with mandelic acid are characterized by higher viscosity values, as compared to hydrogels containing lactobionic acid. The samples of the obtained hydrogels stored for 7 days showed no signs of degradation and their viscosity values were constantly increasing, which proves the ongoing process of creating new bonds between hydroxy acid molecules and chitosan chains. After this time, the hydrogels with mandelic acid revealed higher viscosity values in comparison to hydrogels made with lactobionic acid. Based on the obtained IR spectra, the shifts of the characteristic chitosan bands as a result of interaction with the tested hydroxy acids were analyzed.

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Równowagi asocjacyjne alkilopochodnych mocznika i tiomocznika

Rospenk M., Koll A., Obrzud M.

Wiadomości Chemiczne

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2017

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[Z] 71, 7-8

559--608

EN

The studies and comparison of a series of molecular mono- and di-substituted derivatives of urea and thiourea in solvents of increasing polarity are presented [1–4]. These substances are characterized by a high tendency to self-associate through the formation of intermolecular hydrogen bonds due to the presence in their structure both groups as donors (NH) as well as proton acceptors (C=O) or (C=S). Studies were performed by using IR spectroscopy, method of measuring the average molecular weight and the dipole moments. The experimental data were verified by DFT quantum chemical calculations with B3PW91 correlation functional. Simultaneous use of these techniques alowed establishing not only the efficiency of aggregation, but also the structure and polarity of formed aggregates. It was shown, that in solvents with weak acidic C-H groups the aggregation was strongly limited because of molecular interactions between solute and solvent. The theoretical DFT calculations which included the impact of the environment on the nature of interactions in the complex were carried out [e.g. Scheme 4.1.4]. A combination of geometry optimization in polarizable continuum model (PCM) with the connection of chloroform molecules (1,2-dichloroethane) with urea dimers enabled to obtain the expected theoretical simulation compliance with the experiment. The equilibrium constants were calculated on the basis of data obtained in two independent methods of measurement: IR spectroscopy and measurements of average molecular weights. Good agreement of experimental data of both research techniques were found up to concentration of 0.03 mol/dm3 [Fig. 2.5]. The type of associates have been assessed following the dipole moments measured as a function of concentration, and on the results of density-functional theory (DFT) calculations on the structure and energy of particular species. All of the urea derivatives demonstrated an increase in dipole moment with increased concentration, suggesting linear-type aggregation [Fig. 4.1.3]. Contrastingly, the dipole moments of the N,N-dimethylthiourea and mono-N-alkyl-substituted thioureas decreased with concentration and suggest that cyclic dimers or trimers are formed by C=S…(HR)2N-C=S interactions [Fig. 4.2.2]. The efficiency of self-aggregation was described by use of two equilibrium constants. The first constant, K1, was describing dimer formation and the second constant, K2, the subsequent multimer formation. In N,N’-thioureas aggregation was lower than for the related urea compounds [Table 4.1.1 and Table 4.2.1]. Differences between urea and thiourea derivatives result from the fact that the ureas are stronger bases and, therefore, more active in aggregation.

3

The impact of heat treatment on the components of plant biomass as exemplified by Junniperus sabina and Picea abies

Drygaś B., Depciuch J., Puchalski Cz., Zaguła G.

ECONTECHMOD : An International Quarterly Journal on Economics of Technology and Modelling Processes

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2016

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Vol. 5, No 3

41--50

EN

Torrefaction is the process of drying biomass at high temperatures in order to transform it into biofuels with properties and composition resembling carbon. The impact of high temperature breaks the chains of hemicellulose, lignin and cellulose and degrades the biomass to simpler organic compounds. The aim of this publication was to specify the impact of the duration of the heat treatment on the stability of biomass structures such as lignocellulose illustrated with examples of selected species of conifers. The research material consisted of shoot tips of Junniperus sabina and Picea abies. The material used in the process was air-dried, dried at 150oC and torrefied at temperatures of 200, 250 and 300oC in a LECO camera – TGA 701 apparatus for 30 minutes. Fresh needles and their torrefied products were measured spectroscopically using FTIR Vertex 70v made by Bruker. Microscopic photographs of samples were taken in the scales 10 μm, 20 μm, and 50 μm using the TESCAN VEGA3 scanning electron microscope. The unprocessed plant material did not differ significantly from one another – the FTIR spectra of both plants exhibited the same functional groups. The biomass heat treatment led to significant changes in its chemical composition and topographic changes in the obtained biochars.

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Optical properties of soda-lime-silica glasses doped with peanut shell powder

Aktas B., Albaskar M., Yalcin S., Dogru K.

Archives of Materials Science and Engineering

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2016

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Vol. 82, nr 2

57--61

EN

Purpose: Aim of this paper is to investigate the optical properties of soda-lime-silica (SLS) glasses which doped with different quantities of peanut shell (PS) powder. Design/methodology/approach: UV-Vis and Fourier transform infrared (FTIR) spectroscopy techniques are used to determine optical properties of glass. Findings: It was observed that the colorless and transparent pure SLS glass turned dark green in color with the addition of the PS powder. The glasses doped with PS powder contents ≥1 wt.% were translucent. The maximum absorption in the UV spectrum was observed at wavelengths of 306.20, 292.40, 280.20, and 303.20 nm for SLS glasses doped with PS powder contents of 0.5, 1, 3, and 5 wt.%, respectively. The UV-Vis spectroscopy results also indicated that the amount of light transmitted by the SLS glass decreased with increasing PS powder content. The FTIR absorption spectra of the PS powder-doped SLS glasses exhibited various bands corresponding to the symmetric and asymmetric stretching of the bridging oxygen atoms between the tetrahedra. Research limitations/implications: With the addition of the PS to the SLS glass, samples turned to dark green because of Fe2O3. Future researches must focus on this matter. Originality/value: PS powders are doped to investigate optical properties of glass. Thus, glasses, which have good properties such as economically cheap, bio-friendly, are produced from food wastes.

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Synthesis and properties of magnetic nanoparticles coated with biocompatible compounds

Racuciu M., Creanga D. E., Airinei A., Chicea D., Badescu V.

Materials Science Poland

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2010

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Vol. 28, No. 3

609--616

EN

Syntheses and characterization of two types of systems of magnetic nanoparticles functionalized with biocompatible molecules have been presented. Two colloidal suspensions of iron oxide nanoparticles fabricated by the same co-precipitation method were obtained; the nanoparticles with perchloric acid (HClO4) and with citric acid (C6H8O7), were coated and dispersed in water. The structure at nanometric level of functionalized magnetic nanoparticles was analyzed, using data obtained from magnetic, rheological and structural measurements. Magnetic properties were discussed based on magnetization measurements. Fourier transform infrared absorption spectra have been recorded to obtain additional information on the composition of functionalized magnetic nanoparticles. To assess the optical properties of highly diluted suspensions, UV-VIS absorbance spectra were recorded. Light scattering anisotropy on functionalized magnetic nanoparticles was investigated as well. The dimensional distribution of the nanoparticles physical diameter was comparatively presented using the box-plot statistical method applied to the data provided by transmission electron microscopy.