Superabsorbent materials derived from hydroxyethyl cellulose and bentonite: Preparation,characterization and swelling capacities

Superabsorbent polymers (SAPs) and composites (SAPCs) were prepared entirely by graft copolymerization of polyacrylamide (PAM) onto hydroxyethyl cellulose (HEC), using potassium persulfate (KPS) as an initiator, and N,N′-methylenebisacrylamide (MBA) as a crosslinker, in an aqueous solution. The extent of grafting was evaluated from % grafting efficiency (%GE) for various HEC/AM ratios, and a near optimal ratio was determined. Influences of various preparation parameters, i.e., the ratio of HEC/AM, amount of initiator and crosslinker, reaction temperature and time, and amount of filler on water swelling capacity of SAPs and SAPCs were studied. An FT-IR determination confirmed that the PAM was successfully grafted onto the HEC backbone, by showing absorption bands of the HEC backbone and new absorption bands from the grafted copolymer. The swelling capacity of SAPs and SAPCs depended strongly on different parameters, and the maximum swelling capacity was over 426 g/g and 538 g/g for the SAPs and SAPCs, respectively.     

Evaluation of physicochemical properties of a new group of SiO2/silane/POSS hybrid materials

Preparation of a new group of hybrid fillers, of SiO₂/silane/oligomeric silsesquioxane type, characterised by specific desirable physicochemical properties, was studied. Synthetic SiO₂ was precipitated by the emulsion method. At first, as a result of improved adhesion between SiO₂ and selected POSS compound, SiO₂ surface was functionalised with alkoxysilanes containing characteristics functional groups. Functionalised SiO₂ was used in the process of hybrid filler preparation according to hydrolytic condensation using methacryl POSS® mixture. To evaluate potential application of such fillers, SiO₂ systems, bifunctionalised using innovative method, were thoroughly characterised to determine their physicochemical properties as well as the effectiveness of functionalisation with silanes and POSS compound. Proposed method of SiO₂ surface modification using selected alkoxysilanes and oligosilsesquioxanes is innovative and gives very promising results. Bifunctionalisation of inorganic fillers with those compounds will substantially extended the range of their applications and probably will lead to improvement of mechanical properties of final polymer composites and reduction in the cost of their production which is the main feature of this research. Copyright © 2013 John Wiley & Sons, Ltd.     

Novel antifungal polyene amides from the myxobacterium Cystobacter fuscus: isolation, antifungal activity and absolute structure determination

Three new unstable metabolites, (6E,10Z)-2′-O-methylmyxalamide D (1), 2′-O-methylmyxalamide D (2) and (6E)-2′-O-methylmyxalamide D (3) were isolated from the myxobacterium Cystobacter fuscus. The planar structures were elucidated by spectroscopic analyses to be geometrical isomers of a polyene amide related to a myxobacterial metabolite, myxalamide D (4). Their absolute stereochemistry was determined by synthesis of degradation products. Antifungal activities of 1-3 as well as their acetates were evaluated against the phythopathogenic fungus Phythopthora capsici.     

Conductive properties of TiO2/bacterial cellulose hybrid fibres

In this article, we report the first micellization study of amphiphilic copolymers composed of bacterial medium chain length poly(3-hydroxyalkanoates) (mcl-PHAs). A series of diblock copolymers based on fixed poly(ethylene glycol) (PEG) block (5000 g mol(-1)) and a varying poly(3-hydroxyoctanoate-co-3-hydroxyhexanoate) (PHOHHx) segment (1500-7700 g mol(-1)) have been synthesized using "click" chemistry. These copolymers self-assembled to form micelles in aqueous media. The influence of PHOHHx block molar mass on the hydrodynamic size and on the critical micelle concentration (CMC) has been studied using dynamic light scattering and fluorescence spectroscopy, respectively. With increasing PHOHHx length, narrowly distributed micelles with diameters ranging from 44 to 90 nm were obtained, with extremely low CMC (up to 0.85 mg/L). Cryogenic transmission electron microscopy (Cryo-TEM) showed that micelles took on a spherical shape and exhibited narrow polydispersity. Finally, the colloidal stability of the micelles against physiological NaCl concentration has been demonstrated, suggesting they are promising candidates for drug delivery applications.     

Preparation, structure, and magnetic properties of mesoporous magnetite hollow spheres

Preparation of mesoporous Fe3O4 (magnetite) hollow spheres has been reported using hydrothermal synthesis and calcinations. The carboxyl-functionalized PS spheres were used as the templates coated by Fe3O4 particles and ethylene glycol (EG) as an organic structure directing agent. PS and EG were removed by calcinations method. The surface area after calcination at 500 degrees C is found to be 74 m(2) g(-1). The hollow spheres exhibited the weak ferromagnetism.     

Polyacrylate/silica hybrid materials: A step towards multifunctional properties

Organic/Inorganic hybrid systems present a promising alternative for the creation of high-performance materials due to their biphasic structure that imparts multifunctional properties. The sol-gel process which initiated with the synthesis of inorganic glasses has now become a synthetic route for organic-inorganic assemblies due to several advantages such as mild processing conditions and the freedom to play with the structures of precursors. This versatility of the low-temperature sol-gel process provides an opportunity to engineer both the phases resulting in a synergistic combination or entirely new set of properties fruitful for different applications. This review highlights the several pathways for synthesis of silica particles, the interfacial modification and the classification of hybrid materials based on the method of incorporation of an inorganic moiety in the organic matrix along with the structure-property relationship, and the characterization to develop a fundamental understanding of the process. The nature of bonding between the two different species greatly affects the hybrid nanostructure and thus, the bulk properties of the system. In particular, acrylate/silica system has been focused due to its distinctive properties such as transparency, gloss, and strength that find large-scale application in the field of coatings, plastics and rubbers.Abbreviations: °: Degree; °C: Degree Celsius; ¹H NMR: Proton nuclear magnetic resonance; A°: Angstrom; AHAS: N-(3-acryloxy-2-hydroxyl propyl)-3-amino-propyltriethoxysilane; AIBA: 2,2′-Azobis(2-methylpropionamidine) dihydrochloride; AIBN: 2,2′-Azobis(2-methylpropionitrile); Al: Aluminium; APDMES: Aminopropyldimethylethoxysilane; APTES: 3-Aminopropyltriethoxysilane; ATRP: Atom transfer radical polymerization; CERAMERS: Ceramically Modified Monomers; CTAB: Cetyltrimethylammonium bromide; DFMA: Dodecafluoroheptyl methacrylate; DMF: Dimethylformamide; DPSD: Diphenylsilanediol; FESEM: Field Emission Scanning Electron Microscope; FTIR: Fourier-transform infrared spectroscopy; GPTMS: 3-Glycidoxypropyltrimethoxysilane; HDTMS: Hexadecyltrimethoxysilane; HEMA: 2-Hydroxyethyl methacrylate; HLB: Hydrophilic-Lyophilic Balance; HMDS: Hexamethyldisilazane; HPC: Hydroxypropyl Cellulose; IPN: Interpenetrating Network; KPS: Potassium persulfate; LCST: Lower critical solution temperature; McPTMS: 3-Mercaptopropyltrimethoxysilane; MOI: 2-(methacryloyloxy)ethyl isocyanate; MPEGMA: Monomethoxy-capped poly(ethylene glycol) methacrylate; MPTMS: 3-methacryloxypropyltrimethoxysilane; MTC: 2-(methacryloyl) ethyltrimethylammonium chloride; MTES: Methyltriethoxysilane; MTMS: Methyltrimethoxysilane; NMP: Nitroxide-Mediated Polymerization; ORMOCERs: Organically Modified Ceramics; ORMOSILs: Organically Modified Silica; OTES: Octyltriethoxysilane; OTMS: Octadecyltrimethoxysilane; PAA: Poly(acrylic acid); PDMS: Polydimethylsiloxane; PEO-PPO-PEO: Poly (ethylene oxides)-b-poly (propylene oxides)-b-poly (ethylene oxides); PHPS: Perhydropolysilazane; PMMA: Poly(methyl methacrylate); POSS: Polyhedral Oligomeric Silsesquioxane; PTMO: Poly(tetramethylene oxide); PTMS: Phenyltrimethoxysilane; PTMS: Phenyltrimethoxysilane; PVP: Poly (vinylpyrrolidone); RAFT: Reversible addition- fragmentation chain transfer; Si: Silicon; Sn: Tin; Ta: Tantalum; TBN: 4-(triethoxysilyl)butyronitrile; TEM: Transmission Electron Microscopy; TEMED: N,N,N′,N′-tetramethylethylenediamine; TEOS: Tetraethoxysilane; Tg: Glass-Transition Temperature; THF: Tetrahydrofuran; Ti: Titanium; TMOS: Tetramethoxysilane; UV: Ultraviolet; VTES: Vinyltriethoxysilane; VTMS: Vinyltrimethoxysilane; Zr: Zirconium

• Highlights

• Advantages of hybrid systems over the conventional materials

• Discusses the fundamental aspects of sol-gel chemistry

• Focusses on a detailed classification of hybrid polymers

• Covers different synthetic strategies, properties, and applications in diverse fields

     

Alkyltributylphosphonium chloride ionic liquids: synthesis, physicochemical properties and crystal structure

A series of alkyltributylphosphonium chloride ionic liquids, prepared from tributylphosphine and the respective 1-chloroalkane, C(n)H(2n+1)Cl (where n = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12 or 14), is reported. This work is a continuation of an extended series of tetraalkylphosphonium ionic liquids, where the focus is on the variability of n and its impact on the physical properties, such as melting points/glass transitions, thermal stability, density and viscosity. Experimental density and viscosity data were interpreted using QPSR and group contribution methods and the crystal structure of propyl(tributyl)phosphonium chloride is detailed.     

Synthesis,crystal structure,photoluminescence properties of organic-inorganic hybrid materials based on ethylenediamine bromide

In this work, a new orthorhombic organic-inorganic hybrid single crystal (C₂H₁₀N₂)₂MnBr₄.2Br with-Zero-dimensional structure was synthesized by slow evaporation method at 75 °C. The crystal structure and intermolecular interactions were performed by single crystal X-ray diffraction and Hirshfeld surface. Optical properties of (C₂H₁₀N₂)₂MnBr₄.2Br were systematically studied by Raman, infrared spectrum, UV–vis, photoexcitation spectra, and photoluminescence spectra. The optical band gap (E_g = 2.61 eV) were calculated from the absorption spectra of (C₂H₁₀N₂)₂MnBr₄.2Br. This hybrid materials also had shown good thermal stability (decomposition temperature: 288–660 °C). Finally, photoluminescence measurements showed a strong excitation line at 362 nm and a strong fluorescence at 537 nm which makes it a promising material in luminescence field.     

Development of biopolymer/cellulose/silica nanostructured hybrid materials and their characterization by NMR relaxometry

The objective of this study was to investigate the preparation and properties of hybrid materials composed of poly(lactic acid) (PLA) and poly(lactic acid)/poly(lactic-co-glycolic acid) (PLA/PLGA) blends employing cellulose nanocrystals (CNCs) and/or organophilic silica (R972) as nanoparticles. The CNCs were obtained by acid hydrolysis of commercially available microcrystalline cellulose (MCC). The materials were produced in film form by solution casting. Organophilic silica was incorporated at a ratio of 3 wt.%, and CNCs were added at ratios of 3 wt.% and 5 wt.% in relation to the weight of the polymer matrix. Two series of films were obtained. The first was prepared using only PLA as the matrix, and the second was obtained using blends of PLA and PLGA. The properties of the films were evaluated by X-ray diffractometry, nuclear magnetic resonance, Fourier-transform infrared spectroscopy and measurement of mechanical properties. The results revealed that each nanoparticle, whether added individually or combined with the other type of nanoparticle, induced different final material properties. Cellulose nanocrystals can act as nucleating agents for the crystallization of PLA. There was an improvement in the mechanical performance of films with the addition of CNCs. Further, the incorporation of silica combined with CNCs resulted in the generation of films with the strongest mechanical properties. The results of this study indicate that silica decreases the surface tension between PLA-cellulose and PLA/PLGA-cellulose.     

Synthesis, structure, and physicochemical properties of gel-forming dextran phosphates

Dextran phosphates with the degree of substitution of 0.29–1.09 with phosphoric acid groups and of 0.14–0.83 with carbamate groups were prepared in the orthophosphoric acid-urea system. The effect of the component ratio in the esterifying mixture, temperature, and pressure in the reaction zone on the structure and physicochemical properties of dextran phosphate hydrogels and on the gel fraction yield was examined.     

Thorium compounds with non-metals: Electronic structure, chemical bond, and physicochemical properties

The current state of research on the nature of the chemical bond and the physicochemical properties of binary Th-X (X = H, B, C, N, O, P, S, As, Se, Sb) and ternary (carbonitrides, thorates, and silicates) thorium compounds by modern ab initio methods of the band structure theory is reviewed. The possibilities of the ab initio band structure methods in describing the structural states, phase stability, elasticity characteristics, X-ray emission, absorption, and photoelectron spectra of thorium-containing systems are discussed.     

Preparation and physicochemical and mechanical properties of low-substituted cellulose phosphate fibers

Mechanical and physicochemical properties of cotton and viscose fibers esterified with aqueous solutions containing orthophosphoric acid and urea in different ratios were studied.     

Evolution of rheological properties and local structure during gelation of siloxane-polymethylmethacrylate hybrid materials

Hybrid siloxane-polymethylmethacrylate (PMMA) nanocomposites with covalent bonds between the inorganic (siloxane) and organic (polymer) phases were prepared by the sol gel process through hydrolysis and polycondensation of 3-(trimethoxysilyl)propylmethacrylate (TMSM) and polymerization of methylmethacrylate (MMA) using benzoyl peroxide (BPO) as initiator. The effect of MMA, BPO and water contents on the viscoelastic behaviour of these materials was analysed during gelation by dynamic rheological measurements. The changes in storage (G′) and loss moduli (G′′), complex viscosity (η^*) and phase angle (δ) were measured as a function of the reaction time showing the viscous character of the sol in the initial step of gelation and its progressive transformation to an elastic gel. This study was complemented by ²⁹Si and ¹³C solid-state nuclear magnetic resonance (NMR/MAS) measurements of dried gel. The analysis of the experimental results shows that linear chains are formed in the initial step of the gelation followed by a growth of branched structures and formation of a three-dimensional network. Near the gel point this hybrid material demonstrates the typical scaling behaviour expected from percolation theory.     

Polyelectrolyte/magnetite nanoparticle multilayers: preparation and structure characterization

Polyelectrolyte composite planar films containing a different number of iron oxide (Fe3O4) nanoparticle layers have been prepared using the layer-by-layer adsorption technique. The nanocomposite assemblies were characterized by ellipsometry, UV-vis spectroscopy, and AFM. Linear growth of the multilayer thickness with the increase of the layer number, N, up to 12 reflects an extensive character of this parameter in this range. A more complicated behavior of the refractive index is caused by changes in the multilayer structure, especially for the thicker nanocomposites. A quantitative analysis of the nanocomposite structure is provided comparing a classical and a modified effective medium approach taking into account the influence of light absorption by the Fe3O4 nanoparticles on the complex refractive index of the nanocomposite and contributions of all components to film thickness. Dominant influence of co-adsorbed water on their properties was found to be another interesting peculiarity of the nanocomposite film. This effect, as well as possible film property modulation by light, is discussed.     

Gamma-irradiation of cellulose nanocrystals (CNCs): investigation of physicochemical and antioxidant properties

Gamma irradiation is a common process mostly used for sterilization against bacteria growth. However, when the process is applied to a material, physical and chemical changes may alter its integrity and behaviour. The aim of this study was to observe the effect of γ-irradiation on the surface chemistry of CNCs. The carbonyl content (both carboxylic acid and aldehyde functionalities) was followed to investigate the influence of the irradiation dose. Thermal stability, wettability and antioxidant properties were also measured. Conductometric titration showed that the carboxylic acid groups content (COOH) was increased from 43 mmol COOH kg^?1 CNCs for native CNCs to 631 mmol COOH kg^?1 CNCs when a dose of 80 kGy was applied. These changes were confirmed by FTIR and fluorescence spectroscopy. At high irradiation doses, a significant decrease of approximately 30% was observed in the cellulose degree of polymerization while the aldehyde groups content was increased to 379 mmol CHO kg^?1 CNCs due to the cleavage of glycosidic linkages. These physicochemical changes led to enhanced antioxidant properties of CNCs.     

Synthesis,structure, and antifungal activity of dihydropyridones containing boronate esters

We have prepared a series of novel 2,3‐dihydro‐4‐pyridones containing boronate esters using the aza Diels–Alder reaction with Danishefsky's diene and imines derived from formylphenylboronic acids. This reaction can be carried out in moderate to high yields using Yb(OTf)₃ as a Lewis acid catalyst. Two new boron compounds exhibited moderate antifungal activity (at 100 μg disk⁻¹) using Amphotericin B as a control. © 2009 Wiley Periodicals, Inc. Heteroatom Chem 20:56–63, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20512     

The spinning,structure, and properties of cellulose/chitin blend filaments through HWM method

The aim of this paper is the preparation and characterization of cellulose/chitin blend filaments over the experimental blend ratio scope i.e., 2.89 and 6.46% (w/w) chitin content through high wet modulus (HWM) procedure. The spinnability of the invested solutions was found to vary in the following order: chitin < cellulose < 9.5:0.5 blend < 9:1 blend < 8:2 blend < 5:5 blend (9:1 means the mass ratio of cellulose to chitin, so does 9.5:0.5, 8:2, and 5:5). The cross‐section of the blend filaments is of chrysanthemum shape. It was shown through the SEM photographs that there existed grooves on the surface of filaments, which became coarse with increase in chitin content. Based on the data from X‐ray, sonic velocity, intensity, and hygroscopicity, it is concluded that the degree of crystallinity, dry and wet intensity modulus, degree of orientation, and regain rate of the filaments decreased with increase in chitin content in the experiment scope. The mechanical properties of the blend filaments are much higher than those of Crabyon fiber and normal viscose filaments, which proves that the HWM method is an efficient way of preparing cellulose/chitin blend filaments with satisfactory mechanical properties and processing property. The blend filaments prepared have an effective biostatic effect on Staphylococcus aureus, Escherchia coli, and Corinebaterium michiganence according to different testing standards. Copyright © 2009 John Wiley & Sons, Ltd.     

The cellulose solvent system N,N-dimethylacetamide/lithium chloride revisited: the effect of water on physicochemical properties and chemical stability

The water content in the binary systemN,N-dimethylacetamide/lithium chloride (DMAc/LiCl), acommon cellulose solvent, has been proven to be a crucial parameter. A quickdetermination of water content in DMAc based on the solvatochromism of aUV-active betain probe dye has been developed and validated. An analogousmethod, based on the solvatochromic fluorescence shift ofZelinskij's dye, which strongly depends on thesolventpolarity, was established for water determination in DMAc containing LiCl.Precise physicochemical data of the system DMAc/LiCl, such as density,viscosity, and conductivity, have been obtained. The limiting solubility forLiCl in absolute DMAc is 8.46 wt%. As shown by lightscattering experiments, water in DMAc/LiCl induces aggregation upon standingforlonger periods of time, which is even more prominent for diluted solutions andthose having a poor state of dissolution.     

Effect of preparation of titania sol on the structure and properties of acrylic resin/titania hybrid materials

Acrylic resin/titania organic–inorganic hybrid materials were prepared by mixing titania sol produced by the sol–gel process with synthesized thermoplastic acrylic resins. The effects of the amounts of water and acid on hydrolysis and condensation of the sol–gel precursor (titanium n‐butoxide) were characterized by nuclear magnetic resonance, and their corresponding influences on the structure and properties of the hybrid films were investigated by small‐angle X‐ray scattering (SAXS), atomic force microscopy, dynamical mechanical analysis, an Instron testing machine, and ultraviolet–visible spectroscopy. SAXS indicated an open structure and nanoscale size for the titania phase of the hybrids. Higher titania content and a greater amount of water or acid in the sol–gel process resulted in titania domains that were larger size and had a more compact structure. The mechanical and UV‐shielding properties of the organic polymer obviously were improved with titania embedded. As the amount of water or acid in the sol–gel process increased, integrative mechanical properties decreased, with the amount of water having a greater impact than the amount of acid on the structure and optical properties. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3682–3694, 2004     

A new CoII complex of diniconazole: synthesis,crystal structure and antifungal activity

A new Co^II complex of diniconazole, namely diaqua[(E)‐(RS)‐1‐(2,4‐dichlorophenyl)‐4,4‐dimethyl‐2‐(1H‐1,2,4‐triazol‐1‐yl‐κN⁴)pent‐1‐en‐3‐ol]cobalt(II) dinitrate dihydrate, [Co(C₁₅H₁₇Cl₂N₃O)₃(H₂O)₂](NO₃)₂·2H₂O, was synthesized and characterized by elemental analysis, IR spectroscopy and single‐crystal X‐ray diffraction. Crystal structural analysis shows that the centrosymmetric Co^II cation is coordinated by four diniconazole ligands and two water molecules, forming a six‐coordinated octahedral structure. There are also two free nitrate counter‐anions and two additional solvent water molecules in the structure. Intermolecular O—H...O hydrogen bonds link the complex cations into a one‐dimensional chain. In addition, the antifungal activity of the complex against Botryosphaeria ribis, Gibberella nicotiancola, Botryosphaeria berengriana and Alternariasolani was studied. The results indicate that the complex shows a higher antifungal activity for Botryosphaeria ribis and Botryosphaeria berengriana than diniconazole, but a lower antifungal activity for Gibberella nicotiancola and Alternariasolani.