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1.
J Agric Food Chem ; 67(41): 11527-11535, 2019 Oct 16.
Artigo em Inglês | MEDLINE | ID: mdl-31536347

RESUMO

A magnetic nanoporous organic polymer (M-NOP) was prepared as a new adsorbent with excellent extraction capacity and rapid adsorption kinetics for 5-nitroimidazoles (5-NDZs). Hence, a rapid and effective method was proposed for determination of 5-NDZs in milk by combining M-NOP-based magnetic solid-phase extraction with high-performance liquid chromatography. Main extraction conditions were investigated. Under optimal conditions, good linear response was achieved in a range of 2.4-100 ng mL-1 with a lower detection limit of 0.8-1.0 ng mL-1. High accuracy with a recovery of 80.0-116.0% for the fortified samples, good repeatability with relative standard deviation below 10%, and a high enrichment factor of 97-111 were obtained. The rapid adsorption of 5-NDZs on M-NOP is mainly driven by H-bonding, π-stacking, and polar interactions. Finally, the M-NOP-based method was successfully used to determine 5-NDZs in milk samples. The M-NOP is expected to present promising application in the extraction and quantitative analysis of other compounds.


Assuntos
Magnetismo/métodos , Leite/química , Nitroimidazóis/isolamento & purificação , Polímeros/química , Adsorção , Animais , Bovinos , Cromatografia Líquida de Alta Pressão , Contaminação de Alimentos/análise , Limite de Detecção , Nanoporos , Nitroimidazóis/química , Polímeros/síntese química , Porosidade
3.
Chem Commun (Camb) ; 55(65): 9681-9684, 2019 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-31347618

RESUMO

Here, we report a convenient, fast labeling strategy for the imaging of cell surface sialic acids (SAs, nine-carbon monosaccharides located at the terminals of cell surface sugar chains). This strategy is based on the synthesis of sticky, furry and fluorescent "wool-balls", which are wound into nanoclusters from p-benzoquinone/ethylenediamine polymer "wires". With abundant amino groups at the surface, the wool-balls can easily stick to the C-7 aldehyde group generated at the ends of periodate treated SAs in less than 30 min.


Assuntos
Benzoquinonas/química , Etilenodiaminas/química , Corantes Fluorescentes/química , Nanopartículas/química , Polímeros/química , Ácidos Siálicos/análise , Animais , Benzoquinonas/síntese química , Linhagem Celular Tumoral , Etilenodiaminas/síntese química , Fluorescência , Humanos , Camundongos , Microscopia de Fluorescência/métodos , Neuraminidase/química , Tamanho da Partícula , Polímeros/síntese química , Células RAW 264.7 , Bases de Schiff/síntese química , Bases de Schiff/química , Ácidos Siálicos/química
4.
Chem Soc Rev ; 48(16): 4347-4360, 2019 Aug 12.
Artigo em Inglês | MEDLINE | ID: mdl-31263808

RESUMO

To exert its role of a functional polymer, DNA relies on a molecular self-assembly process that is driven by the interactions of only four units placed in a defined order. Extending the structural diversity of recognition motifs in DNA, to and beyond analogues of the nucleobases, will open doors to self-assembled materials with advanced programmable properties. DNA-inspired systems are becoming useful for numerous applications unachievable by the nucleic acids in their native composition. Potential applications of rationally designed oligo- and polyphosphodiesters reside in the areas of drug delivery, diagnostic signalling and imaging, in systems for efficient energy transfer or the precise ordering on the nanoscale. The field of DNA-inspired phosphodiesters highlights the general value and utility of precision in the composition of oligomers and polymers. In this tutorial review, we will summarize the approaches of directing the self-assembly of DNA-inspired, sequence-specific polyphosphodiesters into soft materials with unique properties. These data expose the so far underexploited potential of DNA-derived systems in solving some of the key issues in various technological areas, such as advanced biomaterials, morphologically defined soft matter or the controlled polymer folding and assembly. Moreover, precise positioning of structurally diverse molecules within a polymer chain creates unmatched opportunities for encoding information on the molecular level and transmitting it further to the microscopic and even macroscopic level via noncovalent interactions.


Assuntos
DNA/química , Polímeros/química , Azidas/química , Lipossomos/química , Compostos Organofosforados/química , Polímeros/síntese química
5.
J Food Sci ; 84(8): 2228-2233, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31269245

RESUMO

Every year, the residues generated by the disposal of packaging materials produced from fossil fuels have been growing, denoting a major environmental problem that can be mitigated by the development of biodegradable materials from natural polymers, particularly edible films. This work aimed at the development of pectin films added by cupuassu puree and chitosan nanoparticles and to evaluate the improvement of the physical-mechanical performance of the composite films. The nanostructures displayed an average size of 110 nm and a zeta potential of approximately +40 mV. The films were produced by casting, and they exhibited manageability, homogeneity, and continuity. Based upon the mechanical analysis of maximum stress and elongation, it was concluded that the nanoparticles functioned as fillers, increasing the toughness of the pectin films. Water vapor permeability assays demonstrated that the nanostructured films containing cupuassu exhibited improved barrier properties. The glass transition temperature of the films was not strongly affected by the addition of nanoparticles. Conversely, the initial degradation temperature decreased with the addition of nanoparticles and cupuassu puree. The outcomes of this research pave a new route for the development of nonconventional food packaging materials.


Assuntos
Cacau/química , Quitosana/química , Embalagem de Alimentos/instrumentação , Nanopartículas/química , Pectinas/química , Extratos Vegetais/química , Polímeros/química , Permeabilidade , Polímeros/síntese química , Vapor/análise
6.
Food Chem ; 299: 125127, 2019 Nov 30.
Artigo em Inglês | MEDLINE | ID: mdl-31301528

RESUMO

An environmentally friendly method which is based on preparation and use of a new composite consisting of poly 3-aminophenol and graphene oxide for solid-phase microextraction of triazole fungicides from natural water and juices is introduced. The composite was synthesized by in-situ polymerization of 3-aminophenol and graphene oxide in weak alkaline media. By using the obtained results from the characterization, a suitable mechanism for polymerization and a proper structure for the polymer were proposed. Under optimal conditions, there are linear relationships between concentration of triazoles and their HPLC peak areas in the range of 0.5-100 µg L-1. The recovery percentages, pre-concentration factors and LOQ for all triazoles were 95.2-98.0%, about 200 and 0.2-0.4 µg L-1, respectively. The offered method was applied for extraction and determination of triazoles from natural water, some juices and it represents a promising alternative method for analysis of triazoles.


Assuntos
Aminofenóis/síntese química , Sucos de Frutas e Vegetais/análise , Fungicidas Industriais/isolamento & purificação , Grafite/síntese química , Triazóis/isolamento & purificação , Água/química , Cromatografia Líquida de Alta Pressão , Fungicidas Industriais/análise , Concentração de Íons de Hidrogênio , Polímeros/síntese química , Microextração em Fase Sólida , Triazóis/análise
7.
J Chromatogr A ; 1602: 48-55, 2019 Sep 27.
Artigo em Inglês | MEDLINE | ID: mdl-31147154

RESUMO

One of the major drawbacks of conventional molecularly imprinted polymers (MIPs) is the requirements of volatility porogenic solvent during polymerization. To overcome the default, MIP based on deep eutectic solvent (DES, a new type of green designer solvents) has been synthesized successfully. To improve the affinity of the MIP based on DES, in this work, a strategy of metallic pivot was suggested in the first time to prepare a highly selective MIP monolithic column. A cetirizine-imprinted polymer was prepared in a DES-based porogen system composed of choline chloride/ ethylene glycol (ChCl-EG) in the presence of Co(Ac)2 as metallic pivot. The resulting DES- Co2+-MIP monolith had 23.5 times higher imprinting factor than the Co2+-free MIP monolith. The characterization of polymers indicated that DES was one of the primary factor influencing the MIP morphology and pore structure. Compared with previous metal-mediated and ionic liquid-based imprinted polymers, the introduction of DES as a porogen in polymerization led to higher imprinting factor (approximately 2.9 - 17.1 times). In addition, the resulting DES-Co2+-MIP can be used as an adsorbent for extraction of cetirizine from ethanol solution with the recoveries of 97.8%. As a conclusion, the metallic pivot is a rather valuable strategy for the synthesis of DES-based MIP monolith with high selectivity.


Assuntos
Técnicas de Química Analítica/métodos , Metais/química , Impressão Molecular , Polímeros/síntese química , Solventes/química , Cetirizina/química , Cetirizina/isolamento & purificação , Etanol/química , Etilenoglicol , Polimerização , Polímeros/química
8.
J Chromatogr A ; 1602: 11-18, 2019 Sep 27.
Artigo em Inglês | MEDLINE | ID: mdl-31160093

RESUMO

Surface molecularly imprinted polymers (MIL-101@MIPs) were prepared using MIL-101 as supporting core, imprinted polymers as selective shell synthesized with coumarin-3-carboxylic acid as dummy template of Zearalenone (ZEN), methacrylic acid as functional monomer, and ethylene glycol dimethacrylate hydroxyethyl methacrylate as cross-linker. The polymers were characterized by scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, and particle-size distribution analyses. MIL-101@MIPs were used as the sorbent to compose the self-made cartridge. The cartridge was used to purify and enrich ZEN from real samples. Under optimized SPE conditions, a self-made cartridge can be reused for at least seven cycles. Elution was monitored with a high-performance liquid chromatography-fluorescence detection system. The linearity of the method ranged within 6.25-250 ng kg-1. The limits of detection ranged within 2.09 - 4.16 ng kg-1, and the limits of quantification ranged within 6.25 -12.50 ng kg-1, respectively. The matrix effects of four real samples were discussed. The spiking recoveries of ZEN ranged within 81.70%-90.10% with relative standard deviations lower than 5.56%. The performance of the self-made cartridge and immunoaffinity column was compared by chromatography.


Assuntos
Grão Comestível/química , Polímeros/síntese química , Extração em Fase Sólida/métodos , Zearalenona/isolamento & purificação , Adsorção , Cromatografia Líquida de Alta Pressão , Cumarínicos/química , Limite de Detecção , Estruturas Metalorgânicas/química , Metacrilatos/química , Impressão Molecular , Oryza/química , Polímeros/química , Triticum/química , Zea mays/química , Zearalenona/análise
10.
Environ Sci Pollut Res Int ; 26(19): 19588-19597, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31077054

RESUMO

In this study, an innovative analytical methodology capable of selectively identifying and quantifying mercury contamination by the association of solid-phase extraction using ion-imprinted polymers as a sorbent phase and differential pulse anodic stripping voltammetry is proposed. To this end, the ion-imprinted polymers were synthesized and characterized by infrared spectroscopy and atomic force microscopy. The sorption capacities and the selectivity of the ion-imprinted polymers were compared to the ones related to the non-imprinted ones. Next, the experimental parameters of this solid-phase extraction method (IIP-SPE) were evaluated univariately. The selectivity of this polymeric matrix against other cations (Cd II, Pb II, and Cu II) was also evaluated. Limits of detection (LOD) and quantification (LOQ) obtained for the here proposed methodology were 0.322 µg L-1 and 1.08 µg L-1, respectively. Also, the precision of 4.0% was achieved. The method was finally applied to three water samples from different sources: for the Piratininga and Itaipu Lagoon waters, Hg II concentrations were below the LOQ and for Vargem River waters a concentration equal to 1.35 ± 0.07 mg L-1 was determined. These results were confirmed by recovery tests, resulting in a recovery of 96.2 ± 4.0%, and by comparison with flame atomic absorption spectrometry, resulting in statistical conformity between the two methods at 95% confidence level.


Assuntos
Monitoramento Ambiental/métodos , Compostos de Mercúrio/análise , Impressão Molecular , Compostos Organomercúricos/análise , Polímeros/síntese química , Poluentes Químicos da Água/análise , Brasil , Eletrodos , Água Doce/química , Limite de Detecção , Polímeros/química , Extração em Fase Sólida
11.
J Agric Food Chem ; 67(24): 6874-6883, 2019 Jun 19.
Artigo em Inglês | MEDLINE | ID: mdl-31144502

RESUMO

We prepared a specific adsorptive nanocarrier for pesticide due to its challenge to cleanup and low detoxification in the treatment after intake, whether intentional or by mistake. We modified the plastic antibody (molecularly imprinted polymer (MIP)) on the surface of persistent luminescence nanoparticle (La3Ga5GeO14: Cr3+, Zn2+, LGGO) as the specific adsorptive nanocarrier for toxic molecules and realized the nanocarrier was widely distributed for absorbing pesticide and real-time in vivo bioimaging. We used LGGO as the core and trichlorphon as the template to prepare the plastic antibody nanocarrier. After in vivo bioimaging and biodistribution of mice, LGGO@MIP could be distributed evenly in the gastrointestinal tract, circulated in the blood for a long time, and finally excreted to achieve the adsorption and removal of pesticide in the body. The LGGO@MIP nanocarrier prepared in this study opens a new way for the treatment of poisoning.


Assuntos
Anticorpos/química , Nanotecnologia/métodos , Praguicidas/metabolismo , Plásticos/química , Imagem Corporal Total/métodos , Adsorção , Animais , Anticorpos/imunologia , Cinética , Luminescência , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Nus , Impressão Molecular , Nanopartículas/química , Nanotecnologia/instrumentação , Praguicidas/química , Plásticos/metabolismo , Polímeros/síntese química , Polímeros/química , Triclorfon/química , Triclorfon/metabolismo , Imagem Corporal Total/instrumentação
12.
AAPS PharmSciTech ; 20(5): 193, 2019 May 21.
Artigo em Inglês | MEDLINE | ID: mdl-31115746

RESUMO

Three polymers, polyvinylpyrrolidone (PVP K30), hydroxypropyl methyl cellulose (HPMC E5), and Kollidone VA64 (PVP-VA64), have been assessed for their impact on the nucleation and crystal growth of indomethacin (IND) from supersaturation solutions. PVP was the most effective inhibitor on IND nucleation among three polymers, but the effect of three polymers on inhibiting nucleation is quite limited when the degree of supersaturation S is higher than about 9. Analysis of the nucleation data by classical nucleation theory model generally afforded good data fitting with the model and showed that addition of polymers may affect the crystal/solution interfacial free energy γ and also the pre-exponential kinetic factor. PVP-VA showed better inhibitory effects on crystal growth of IND when the polymer concentration is high (0.1%, w/w) as reflected by the crystal growth inhibition factor R, and PVP exhibited relatively stronger effects on inhibiting crystal growth at low polymer concentrations (0.005%, w/w). The crystal growth inhibitory effect of polymers should be attributable to the retardation of the surface integration of the drug, and such effect should also be polymer and drug dependent. The enhancement of supersaturation level of IND should be attributable to both nucleation and crystal growth inhibition by polymers. The nucleation and crystal growth rate of α-polymorph IND is higher than that of γ-polymorph, and α-polymorph is the predominant form appeared in supersaturated solutions. A rational selection of the appropriate polymer for specific drug is critical for developing supersaturated drug delivery formulations.


Assuntos
Anti-Inflamatórios não Esteroides/síntese química , Indometacina/síntese química , Polímeros/síntese química , Anti-Inflamatórios não Esteroides/farmacocinética , Cristalização/métodos , Composição de Medicamentos , Derivados da Hipromelose/síntese química , Derivados da Hipromelose/farmacocinética , Indometacina/farmacocinética , Soluções Farmacêuticas/síntese química , Soluções Farmacêuticas/farmacocinética , Polímeros/farmacocinética , Povidona/síntese química , Povidona/farmacocinética , Solubilidade
13.
AAPS PharmSciTech ; 20(5): 196, 2019 May 23.
Artigo em Inglês | MEDLINE | ID: mdl-31123934

RESUMO

Undesired-burst release effect is observed in a freely water-soluble drug formulated into a gastro-floating formulation with effervescent (GFFE) delivery system. In order to address this limitation, interpolymer complex (IPC) of two swellable and non-soluble polymers, poly-ammonium methacrylate and poly-vinyl acetate, was incorporated into hydroxypropyl methyl cellulose (HPMC)-based matrix GFFE. This research studied the effect and interaction of the IPC-HPMC blending on the drug release of GFFE using a freely water-soluble drug, metformin HCl, under different threshold concentration levels and curing effect. The interaction between the IPC and HPMC was characterized using vibrational spectroscopy and thermal analyses under curing and swelling conditions. Anti-solvent followed by lyophilization had better physicochemical and physicomechanic properties than spray dying technique. The interaction was observed by a specific shifting of the vibrational peaks and alteration of the thermal behavior pattern. These effects altered the drug release behavior. Thereafter, the IPC reduced burst release effects in the initial time and during testing, and the IPC improved the HPMC matrix robustness under mechanical stress testing below threshold concentration of HPMC matrix formulated in the GFFE.


Assuntos
Fármacos Gastrointestinais/síntese química , Derivados da Hipromelose/síntese química , Polímeros/síntese química , Água/química , Preparações de Ação Retardada/síntese química , Preparações de Ação Retardada/farmacocinética , Composição de Medicamentos/métodos , Liberação Controlada de Fármacos , Fármacos Gastrointestinais/farmacocinética , Derivados da Hipromelose/farmacocinética , Polímeros/farmacocinética , Solubilidade , Comprimidos
14.
Carbohydr Polym ; 216: 149-156, 2019 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-31047051

RESUMO

A novel porous ß-cyclodextrin/pillar[5]arene copolymer was prepared using tetrafluoroterephthalonitrile as cross-linker for rapid removal of variety of organic pollutants. The copolymer was characterized by water contact angle, scanning electron microscope, FT-IR spectrum, solid-state 13C NMR spectrum, thermo-gravimetric analysis, nitrogen adsorption-desorption isotherms, and elemental analysis. Results showed that the co-polymer had good water immersibility, co-existing micro-/meso-pores, and a large specific surface area (BET) of 479 m2/g. The copolymer presented high adsorption capacity with the maximum adsorption capacity of 258 mg/g for bisphenol A and good reusability and reproducibility. It also showed fast binding kinetics with the apparent second-order rate constants of 0.109-0.179 g/mg·min and simultaneously rapid removal ability with removal efficiencies of 74-90% within 30 s for variety of organic pollutants. The new copolymer can be potentially used as adsorbent for rapidly removing a wide range of organic pollutants in wastewater.


Assuntos
Calixarenos/química , Polímeros/química , Poluentes Químicos da Água/química , Água/química , beta-Ciclodextrinas/química , Adsorção , Calixarenos/síntese química , Polímeros/síntese química , Porosidade , Reprodutibilidade dos Testes , Purificação da Água/métodos , beta-Ciclodextrinas/síntese química
15.
Carbohydr Polym ; 216: 167-179, 2019 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-31047053

RESUMO

In this paper, acid-catalyzed conversion of nine sugars (xylose, glucose, fructose, galactose, sucrose, maltose, lactose, raffinose, and ß-cyclodextrin) with different sizes, steric structures and functionalities were investigated and impacts of the varied sugars on structures of resulting polymers were focused. Under similar reaction conditions, the yields of the carbon materials (insoluble polymers) formed followed the order: xylose ¼ lactose > galactose > ß-cyclodextrin > maltose > sucrose > fructose > glucose > raffinose. Increasing temperature enhanced transformation of soluble oligomers into insoluble ones. Morphologies of the carbon materials were closely related to sugar structures. Diameters of carbon materials (microsphere form) obtained from the disaccharides and oligosaccharides were larger than that of monosaccharides. Furthermore, the microspheres from oligosaccharides had a higher affinity to each other, resulting from continued polymerization as some reactive functionalities were retained in carbon materials. In addition, graphite structure was formed in the carbon materials, even at 160 °C.


Assuntos
Monossacarídeos/química , Oligossacarídeos/química , Polímeros/química , beta-Ciclodextrinas/química , Catálise , Hidrólise , Microesferas , Estrutura Molecular , Polímeros/síntese química , Solubilidade , Ácidos Sulfúricos/química , Temperatura Ambiente
16.
Molecules ; 24(9)2019 May 07.
Artigo em Inglês | MEDLINE | ID: mdl-31067638

RESUMO

Diketopyrrolopyrrole (DPP) is an important type of π-conjugated building block for high-performance organic electronic materials. DPP-based conjugated materials are usually synthesized via Suzuki, Stille, or Negishi cross-coupling reactions, which require organometallic precursors. In this paper, a series of novel phenyl-cored DPP molecules, including five meta-phenyl-cored molecules and four para-phenyl-cored molecules, have been synthesized in moderate to good yields, in a facile manner, through the Pd-catalyzed direct arylation of C-H bonds, and their optoelectrical properties have been investigated in detail. All new molecules have been fully characterized by NMR, MALDI-TOF MS, elemental analysis, UV-visible spectroscopy, and cyclic voltammetry. This synthetic strategy has evident advantages of atom- and step-economy and low cost, compared with traditional cross-coupling reactions.


Assuntos
Estrutura Molecular , Polímeros/síntese química , Pirróis/síntese química , Catálise , Eletrônica , Polímeros/química , Pirróis/química
17.
Molecules ; 24(9)2019 May 07.
Artigo em Inglês | MEDLINE | ID: mdl-31067770

RESUMO

During the last number of years a variety of crystallization-driven self-assembly (CDSA) processes based on semicrystalline block copolymers have been developed to prepare a number of different nanomorphologies in solution (micelles). We herein present a convenient synthetic methodology combining: (i) The anionic polymerization of 2-vinylpyridine initiated by organolithium functionalized phosphane initiators; (ii) the cationic polymerization of iminophosphoranes initiated by -PR2Cl2; and (iii) a macromolecular nucleophilic substitution step, to prepare the novel block copolymers poly(bistrifluoroethoxy phosphazene)-b-poly(2-vinylpyridine) (PTFEP-b-P2VP), having semicrystalline PTFEP core forming blocks. The self-assembly of these materials in mixtures of THF (tetrahydrofuran) and 2-propanol (selective solvent to P2VP), lead to a variety of cylindrical micelles of different lengths depending on the amount of 2-propanol added. We demonstrated that the crystallization of the PTFEP at the core of the micelles is the main factor controlling the self-assembly processes. The presence of pyridinyl moieties at the corona of the micelles was exploited to stabilize gold nanoparticles (AuNPs).


Assuntos
Substâncias Macromoleculares/química , Nanopartículas Metálicas/química , Micelas , Polímeros/química , Cristalização , Ouro , Substâncias Macromoleculares/síntese química , Compostos Organofosforados/síntese química , Compostos Organofosforados/química , Tamanho da Partícula , Polimerização , Polímeros/síntese química , Polivinil/síntese química , Polivinil/química , Solventes/química
18.
Molecules ; 24(9)2019 May 02.
Artigo em Inglês | MEDLINE | ID: mdl-31052603

RESUMO

Bio-based polyesters are a new class of materials that are expected to replace their fossil-based homologues in the near future. In this work, poly(propylene 2,5-furandicarboxylate) (PPF) nanocomposites with graphene nanoplatelets were prepared via the in-situ melt polycondensation method. The chemical structure of the resulting polymers was confirmed by 1H-NMR spectroscopy. Thermal stability, decomposition kinetics and the decomposition mechanism of the PPF nanocomposites were studied in detail. According to thermogravimetric analysis results, graphene nanoplatelets did nοt affect the thermal stability of PPF at levels of 0.5, 1.0 and 2.5 wt.%, but caused a slight increase in the activation energy values. Pyrolysis combined with gas chromatography and mass spectroscopy revealed that the decomposition mechanism of the polymer was not altered by the presence of graphene nanoplatelets but the extent of secondary homolytic degradation reactions was increased.


Assuntos
Alcenos/química , Grafite/química , Nanocompostos/química , Polímeros/química , Cinética , Espectroscopia de Ressonância Magnética , Polímeros/síntese química , Termodinâmica
19.
Molecules ; 24(9)2019 Apr 29.
Artigo em Inglês | MEDLINE | ID: mdl-31035708

RESUMO

Pincer-type [Cnaphthyl, Npyridine, Namido]HfMe2 complex is a flagship among the post-metallocene catalysts. In this work, various pincer-type Hf-complexes were prepared for olefin polymerization. Pincer-type [Namido, Npyridine, Namido]HfMe2 complexes were prepared by reacting in situ generated HfMe4 with the corresponding ligand precursors, and the structure of a complex bearing 2,6-Et2C6H3Namido moieties was confirmed by X-ray crystallography. When the ligand precursors of [(CH3)R2Si-C5H3N-C(H)PhN(H)Ar (R = Me or Ph, Ar = 2,6-diisopropylphenyl) were treated with in situ generated HfMe4, pincer-type [Csilylmethyl, Npyridine, Namido]HfMe2 complexes were afforded by formation of Hf-CH2Si bond. Pincer-type [Cnaphthyl, Sthiophene, Namido]HfMe2 complex, where the pyridine moiety in the flagship catalyst was replaced with a thiophene unit, was not generated when the corresponding ligand precursor was treated with HfMe4. Instead, the [Sthiophene, Namido]HfMe3-type complex was obtained with no formation of the Hf-Cnaphthyl bond. A series of pincer-type [Cnaphthyl, Npyridine, Nalkylamido]HfMe2 complexes was prepared where the arylamido moiety in the flagship catalyst was replaced with alkylamido moieties (alkyl = iPr, cyclohexyl, tBu, adamantyl). Structures of the complexes bearing isopropylamido and adamantylamido moieties were confirmed by X-ray crystallography. Most of the complexes cleanly generated the desired ion-pair complexes when treated with an equivalent amount of [(C18H37)2N(H)Me]+[B(C6F5)4]-, which showed negligible activity in olefin polymerization. Some complexes bearing bulky substituents showed moderate activities, even though the desired ion-pair complexes were not cleanly afforded.


Assuntos
Alcenos/química , Háfnio/química , Polímeros/química , Catálise , Cristalografia por Raios X , Espectroscopia de Ressonância Magnética , Modelos Moleculares , Estrutura Molecular , Polimerização , Polímeros/síntese química
20.
Top Curr Chem (Cham) ; 377(3): 16, 2019 May 20.
Artigo em Inglês | MEDLINE | ID: mdl-31111247

RESUMO

Elemental sulfur is an abundant and inexpensive chemical feedstock, yet it is underused as a starting material in chemical synthesis. Recently, a process coined inverse vulcanization was introduced in which elemental sulfur is converted into polymers by ring-opening polymerization, followed by cross-linking with an unsaturated organic molecule such as a polyene. The resulting materials have high sulfur content (typically 50-90% sulfur by mass) and display a range of interesting properties such as dynamic S-S bonds, redox activity, high refractive indices, mid-wave IR transparency, and heavy metal affinity. These properties have led to a swell of applications of these polymers in repairable materials, energy generation and storage, optical devices, and environmental remediation. This article will discuss the synthesis of polymers by inverse vulcanization and review case studies on their diverse applications. An outlook is also presented to discuss future opportunities and challenges for further advancement of polymers made by inverse vulcanization.


Assuntos
Técnicas de Química Sintética/métodos , Polimerização , Polímeros/síntese química , Compostos de Enxofre/síntese química , Enxofre/química , Reagentes para Ligações Cruzadas/química , Eletrodos , Recuperação e Remediação Ambiental/métodos , Metais Pesados/isolamento & purificação , Dispositivos Ópticos , Polímeros/química , Compostos de Enxofre/química
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