Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 8 de 8
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
Materials (Basel) ; 14(16)2021 Aug 17.
Artigo em Inglês | MEDLINE | ID: mdl-34443139

RESUMO

The growing ecological awareness of society created the tendency to replace petrochemically based materials with alternative energy carriers and renewable raw materials. One of the most requested groups of polymer materials with significant technological importance is thermoplastic elastomers (TPE). They combine the properties of elastomers such as flexibility with the typical properties of thermoplastics, like easy processing. Herein, one compares the influence of rigid segments on the properties of copoly(ester-ether). Thermoplastic polyesters based on bio-1,6-hexanediol and terephthalic (T), furanic (F), and napthalate (N) diesters, i.e., PHT, PHF, and PHN, were obtained employing melt polycondensation. Additionally, to grant elastic properties of polyesters, systems containing 50 wt.% of bio-based polyTHF®1000 (pTHF) with a molecular mass of 1000 g/mol, have been prepared. The composition and chemical structure have been determined by 1H nuclear magnetic resonance (NMR) and Fourier transformed infrared spectroscopy (FTIR) analyses. The temperatures corresponding to phase transition changes were characterized by differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA) analyses. The crystalline structure was examined by X-ray diffraction (XRD) analysis. Additionally, the influence of pTHF-rich segment on the tensile properties, water absorption, as well as thermal and thermo-oxidative stability, has been analyzed. It was found that incorporation of soft phase allows creation of thermoplastic elastomers with tensile characteristics comparable to the commercially available ones, by means of elongation at break higher than 500%, low values of tensile modulus, without exhibiting yield point.

2.
Polymers (Basel) ; 13(3)2021 Jan 27.
Artigo em Inglês | MEDLINE | ID: mdl-33513765

RESUMO

A series of poly(hexamethylene 2,5-furanodicarboxylate)-block-poly(tetrahydrofuran) (PHF-b-F-pTHF) copolymers were synthesized using a two-stage procedure, employing transesterification and polycondensation. The content of pTHF flexible segments varied from 25 to 75 wt.%. 1H nuclear magnetic resonance (NMR) and Fourier transformed infrared spectroscopy (FTIR) analyses were applied to confirm the molecular structure of the materials. Differential scanning calorimetry (DSC), dynamic mechanical measurements (DMTA), and X-ray diffraction (XRD) allowed characterizing the supramolecular structure of the synthesized copolymers. SEM analysis was applied to show the differences in the block copolymers' morphologies concerning their chemical structure. The influence of the number of flexible segments in the copolymers on the phase transition temperatures, thermal properties, as well as the thermo-oxidative and thermal stability was analyzed. TGA analysis, along with tensile tests (static and cyclic), confirmed the utilitarian performance of the synthesized bio-based materials. It was found that an increase in the amount of pTHF caused the increase of both number-average and weight-average molecular weights and intrinsic viscosities, and at the same time causing the shift of the values of phase transition temperatures toward lower ones. Besides, PHF-b-F-pTHF containing 75 wt.% of F-pTHF units was proved to be a promising thermoplastic shape memory polymer (SMP) with a switching temperature of 20 °C.

3.
Sci Rep ; 10(1): 646, 2020 01 20.
Artigo em Inglês | MEDLINE | ID: mdl-31959807

RESUMO

In a more synthetical approach to the study of ion-specific phenomena, four dipodal bis(guanidinium) siloxanes have been synthesized starting from glycine, ß-alanine, γ-aminobutanoic acid, L-proline and 1,3-bis(3-aminopropyl)tetramethyldisiloxane. Together with their non-amide progenitor they were comparatively studied in regards to their interactions with nine different anions: sulphate, chromate, molybdate, benzoate, chloride, azide, nitrite, nitrate and thiocyanate. Their aqueous solubilities, form, 1H NMR and FT-IR spectra were examined while searching for anion-specific interactions falling in- or outside of the Hofmeister series. We show that although the "chao-" and "kosmotropic" ions affect the properties of solutions in a predictable way, more selective cation-anion pairing is responsible for phase separation and crystallinity. As a prominent example, crystal structure of one of the benzoate salts was successfully obtained and reveals a synergy of hydrophobic packing, ionic and hydrogen bonding. Immobilized but still flexible siloxane bridges give rise to crystals described by P 42/n space group and neatly segregated into hydro- and lipophilic sections.


Assuntos
Aminoácidos/química , Guanidina/síntese química , Íons/química , Silanos/síntese química , Ânions/química , Ácido Butírico/química , Cristalização , Glicina/química , Guanidina/química , Ligação de Hidrogênio , Interações Hidrofóbicas e Hidrofílicas , Prolina/química , Silanos/química , Solubilidade , Soluções , Relação Estrutura-Atividade , Água , beta-Alanina/química
4.
Molecules ; 24(18)2019 Sep 06.
Artigo em Inglês | MEDLINE | ID: mdl-31500119

RESUMO

Ionic liquids based on different l-amino acids (glycine, l-valine, l-leucine, l-isoleucine, l-histidine, l-methionine, l-tyrosine, l-tryptophan, l-arginine, and l-threonine) and different cations (tetrabutylammonium (TBA), tributylmethylammonium (tBMA), didecyldimethylammonium (DDA), (2-hydroxyethyl)trimethylammonium (choline) (Chol), alkyl(C12-C14) dimethylbenzylammonium (benzalkonium) (BA), dodecyltrimethylammonium (DDTMA), hexadecyltrimethylammonium (HDTMA), octadecyltrimethylammonium (ODTMA) and 1-ethyl-3-methylimidazolium (EMIM)) have been synthesized and characterized by NMR and FTIR. Viscosity, specific rotation, surface activity, thermal stability (TG), and phase transformations (DSC) have been determined and compared with available data. Furthermore, benzalkonium, didecyldimethylammonium, dodecyltrimethylammonium, hexadecyltrimethylammonium, and octadecyltrimethylammonium amino acid ionic liquids have been shown to exhibit surface activity. The dissolution of cellulose in amino acid ionic liquids (AAILs) composed of various cations was also investigated. Cellulose was only dissolved in EMIM salts of amino acids. In particular, the influence of the cation type on selected physicochemical and spectroscopic properties were discussed. The article is a mini review on amino acid ionic liquids.


Assuntos
Aminoácidos/química , Imidazóis/química , Líquidos Iônicos/química , Compostos de Amônio Quaternário/química , Cátions/química , Celulose/química , Espectroscopia de Ressonância Magnética , Relação Estrutura-Atividade
5.
Int J Biol Macromol ; 82: 798-805, 2016 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-26478091

RESUMO

This is the first study on the surface modification of a hemocyanin from marine snail Rapana thomasiana (RtH) with series of imidazolium-based amino acid ionic liquids [emim][AA]. We monitored the induced by [emim][AA] conformational changes in RtH molecule and evaluated the effect of these ionic liquids (ILs) on the protein thermal stability. The cytotoxicity of all obtained RtH-[emim][AA] complexes was assessed toward breast cancer cells (MCF-7) and murine fibroblasts (3T3). As a whole, even small amounts of the tested ILs altered the secondary structure of RtH. The thermal denaturation of RtH in presence of [emim][AA] displayed multi-component transitions, which were shifted toward lower temperatures in comparison to those estimated for the native RtH. The profiles of the RtH-IL calorimetric curves show a clear dependence on the structure of the added salts. In addition, all RtH-[emim][AA] complexes exhibited an enhanced antiprofilerative activity of toward MCF-7 cells in comparison to that of the native RtH. The best results are observed for RtH-[emim][Leu], RtH-[emim][Trp] or RtH-[emim][Ile], which applied in concentration of 700 µg/mL inhibited the MCF-7 cell viability (for 24h) by 66, 63 and 53%, respectively. In addition, these IL-RtH complexes were less cytotoxic to 3T3 cells, i.e. they exhibited some cell specificity.


Assuntos
Antineoplásicos/química , Antineoplásicos/farmacologia , Gastrópodes , Hemocianinas/química , Hemocianinas/farmacologia , Líquidos Iônicos/química , Células 3T3 , Animais , Neoplasias da Mama , Sobrevivência Celular/efeitos dos fármacos , Feminino , Fibroblastos/efeitos dos fármacos , Fibroblastos/metabolismo , Humanos , Líquidos Iônicos/síntese química , Células MCF-7 , Camundongos , Estabilidade Proteica , Espectroscopia de Infravermelho com Transformada de Fourier , Termodinâmica
6.
Molecules ; 18(5): 4986-5004, 2013 Apr 29.
Artigo em Inglês | MEDLINE | ID: mdl-23629755

RESUMO

Amino acid ionic liquid-supported Schiff bases, derivatives of salicylaldehyde and various amino acids (L-threonine, L-valine, L-leucine, L-isoleucine and L-histidine) have been investigated by means of various spectroscopic techniques (NMR, UV-Vis, IR, MS) and deuterium isotope effects on ¹³C-NMR chemical shifts. The results have shown that in all studied amino acid ionic liquid-supported Schiff bases (except the L-histidine derivative) a proton transfer equilibrium exists and the presence of the COO⁻ group stabilizes the proton transferred NH-form.


Assuntos
Aldeídos/química , Aminoácidos/química , Bases de Schiff/química , Análise Espectral/métodos
7.
J Nat Prod ; 70(9): 1539-41, 2007 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-17822300

RESUMO

Through bioactivity-guided fractionation, two volatile benzaldehyde derivatives ( 1 and 2) were isolated from a cellulose-matrix culture of the Basidiomycete Sarcodontia crosea (syn. S. setosa), where the fungus was grown on a growth medium-impregnated thick chromatographic paper. The structures of 1 and 2 were elucidated mainly by 2D NMR techniques as 4-(furan-3-yl)benzaldehyde and 4-(5-oxotetrahydrofuran-3-yl)benzaldehyde, respectively. Compound 1 is a new natural product, while 2 has been synthesized previously. They are considered to contribute to the odor of the fungus, which is an important character for identification of the species. They were weakly antifungal toward several phytopathogenic fungi but less potent against bacteria in microdilution assays.


Assuntos
Anti-Infecciosos/isolamento & purificação , Basidiomycota/química , Benzaldeídos/isolamento & purificação , Anti-Infecciosos/química , Anti-Infecciosos/farmacologia , Benzaldeídos/química , Benzaldeídos/farmacologia , Carpóforos/química , Malus/microbiologia , Testes de Sensibilidade Microbiana , Estrutura Molecular , Reino Unido
8.
Basic Clin Pharmacol Toxicol ; 97(4): 257-60, 2005 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-16176563

RESUMO

Occasional or suicidal methanol intoxications are a permanent problem for most Poisoning Centers around the World. Therefore it is important to look for new diagnostic and clinical prognostic methods. In the present paper 5 cases of methanol intoxication were analyzed. At first the methanol concentrations in blood and urine were estimated with headspace gas chromatography technique. Next the urine samples were examined with 1H NMR spectroscopy, then the levels of ethanol, methanol and its metabolite, formate, lactate and trimethylamine-N-oxide with dimethylamine were evaluated. The concentrations of the above compounds were correlated with the patient's clinical status, the level of ethanol and methanol and biochemical parameters. The results indicate the correlation between clinical course of intoxication, prognostication and lactate level. There were no significant parallels for formate level as acidosis causing metabolite and initial methanol levels. In the urine samples of intoxicated patients the increased trimethyl-N-oxide and dimethylamine levels were observed, which may indicate renal cortex damage. Contrary to the opinion of some clinicians, methanol intoxication may be connected with renal functional disturbances. 1H NMR examination of urine appears to be an excellent tool to evaluate the clinical course of methanol intoxication.


Assuntos
Ácido Láctico/urina , Metanol/envenenamento , Metanol/urina , Dimetilaminas/urina , Feminino , Humanos , Rim/efeitos dos fármacos , Rim/metabolismo , Espectroscopia de Ressonância Magnética , Masculino , Metanol/sangue , Metilaminas/urina
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...