Volume 90, Issue 6

Authors present a phenomenological view on dielectric relaxation in polymer electrolytes, which is monitored by electrochemical impedance spectroscopy. Molecular interaction of polymer chains with salt molecules (or dipole-dipole interaction between segments and salt molecules) leads to dipolar molecular entities. Frequency-dependant impedance spectra are the key quantities of the interest for determination of electric properties of materials and their interfaces with conducting electrodes. Salt concentration serves as parameter. Bulk and interfacial properties of the samples are discussed in terms of impedance ( Z * ) and modulus ( M * ) spectra. We focus on two different classes of systems, i.e. high molar mass of poly(ethylene oxide) (PEO)+lithium perchlorate (LiClO 4 ) (i.e. the inorganic salt) and epoxidized natural rubber (ENR-25) with 25 mol% of epoxide content+LiClO 4 . Impedance spectra with salt content as parameter tell us that we have interaction between dipolar entities leading to dispersion of relaxation times. However, as scaling relations show, dispersion of relaxation times does not depend on salt content in the PEO system. The relaxation peak for the imaginary part of electric modulus ( M ″) provides information on long-range motion of dipoles. Summarizing the results from imaginary part of impedance spectrum ( Z ″), tan δ (imaginary/real of permittivities) and M ″ for the two systems under the discussion, PEO behaves like a mixture of chains with dipoles. There are interactions between the dipoles, but they are relaxing individually. Therefore, we see PEO-salt system as a polymer electrolyte where only a tiny fraction of added salt molecules becomes electrically active in promoting conductance. However, ENR-25-salt system behaves just as a macroscopic dipole and it can not display electrode polarization or electric relaxation because there is no mobility of individual dipoles. Hence, ENR-25-salt does not form a polymer electrolyte in the classic sense.

Scattering techniques (i.e. light scattering, X-ray scattering, or neutron scattering) are very powerful tools to gain insights into structural and thermodynamic properties of matter which often cannot be obtained by other methods. While classical thermodynamics is independent of length scale or applies for indefinitely long length scale, scattering can disclose thermodynamic properties like the free energy or free enthalpy as functions of length scale. Scattering is caused by density or composition fluctuations, which are functions of the length scale in one- or multicomponent systems. Therefore scattering techniques can give informations about the size, shape and molecular weight of scattering objects, their thermodynamic interactions with a surrounding matrix and their dynamics if correlations of the fluctuations as function of time are investigated (i.e. dynamic light scattering). As scattering techniques are less intuitive in comparison to complementary techniques, i.e. microscopic techniques, the aim of this article is to highlight some relevant relationships with a focus on polymer systems. This may encourage polymer scientists to consider the use of scattering techniques to learn more about the thermodynamics of their systems and/or to gain informations about their structural properties.

Simultaneous rotations of sample and X-ray detected counter are needed to evaluate orientation distribution of crystallites and amorphous chains oriented predominantly parallel to the film surface in addition to exact diffraction peak profiles obtained without the complicated intensity corrections. The rotation mode is known as “ θ –2 θ scanning” system ( θ : film, 2 θ : counter). The system has been mainly used in research and development institutes. However, such instruments are not produced at present. Recently, small angle X-ray scattering (SAXS) and wide angle X-ray diffraction (WAXD) intensities have been measured by using X-ray beam generated along one direction. The brand name of the instrument is “a simultaneous SAXS and WAXD measuring instrument”. The X-ray beam generated by the instrument has surely high luminance providing high degree resolution of peak profiles by diffraction and/or scattering. The sample stage and detector, however, are fixed, since the intensities for SAXS and WAXD are obtained by the digital display of the number of X-ray photons detected on the imaging plate. Such optical system contains controversial defect on evaluating orientation of crystal planes parallel to the surface of films prepared by T-die and inflation methods as well as the exact profile. The imaging plate cannot detect the diffraction intensity from the crystal planes existing in the angle range between incident beam and Bragg angle associated with the diffraction peak position of the individual crystal planes.

Hydrosilylation reaction of 2.4.6.8-tetrahydro-2.4.6.8-tetramethylcyclotetrasiloxane (D 4 H ) with allyl acetoacetate at 1:4.1 molar ratios of initial compounds in the presence of platinum hydrochloric acid (0.1 M solution in THF), Karstedt’s catalyst (Pt 2 [(VinSiMe 2 ) 2 O] 3 ) and platinum on the carbon have been carried out and D 4 R type compounds obtained. Reaction order, rate constants and activation energies for hydrosilylation reactions in the presence of Karstedt’s catalyst have been determined. Ring-opening polymerization reaction of D 4 R in the presence of catalytic amounts of powder-like potassium hydroxide has been carried out. A linear methylsiloxane oligomer with regular arrangement of propyl acetoacetate groups in the side chain has been obtained. The synthesized methylorganocyclotetrasiloxane and oligomers were studied by FTIR, 1 H, 13 C and 29 Si NMR spectroscopy. Comb-type oligomers were characterized by gel-permeation chromatography, wide-angle X-ray diffractometry and differential scanning calorimetry. Solid oligomer electrolyte membranes have been obtained via sol–gel processes involving lithium trifluoromethylsulfonate (triflate) or lithium bis(trifluoromethylsulfonyl)imide. The specific volumetric electrical conductivity of the membranes at room temperature covers a wide range, from 10 −10 to 10 −4 S · cm −1 , and depends on the structures of grafted anion receptors and the polymer backbones. Higher values of the specific conductivity are seen for the membranes containing triflate.

We have obtained composites on the basis of dry bamboo powders and in turn several binders, including polyethylene (PE) and alkoxysilanes. The composites were studied by Fourier transformation infrared spectroscopy (FTIR), optical and scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). Some mechanical properties were determined along with thermal stability by thermogravimetry; water absorption was also determined. FTIR results show formation of primary chemical bonds between bamboo surface active groups and the binders. Mechanical property improvement goes symbatically with the thermal stability.

There is considerable interest in the development of simple methods for quantifying production of the biodegradable polyester poly(3-hydroxybutyrate) [P(3HB)] by bacteria. Cells of Cupriavidus necator were grown on agar medium containing different concentrations of glucose (10–25 g/L) as a sole carbon source. Trace amounts (100±5 μg) of dried C. necator cells were directly subjected to thermally assisted hydrolysis and methylation-gas chromatography (THM-GC) in the presence of tetramethylammonium hydroxide (TMAH). On the resulting chromatograms, a series of characteristic peaks, attributed to the THM products from poly(3-hydroxybutylate) accumulated in the bacterial cells, were clearly observed without any interfering component. Based on the peak intensities, the contents of P(3HB) in C. necator were determined precisely and rapidly without using any cumbersome sample pretreatment. Furthermore, the values of the P(3HB) contents coincided overall with those obtained by the conventional method involving solvent extraction followed by gravimetric determination.

Green synthesis of room temperature ionic liquids (RTILs), are presented as friendly and challenging solvents for the effective dissolution of oil palm-lignocellulosic biomass. A series of Bronsted acidic-ionic liquids were prepared by the direct neutralization of diethyl dimethyl ammonium hydroxide with several (economical and environmental friendly) Bronsted acids as RTILs. The structural and physicochemical characterization was performed by applying various techniques as Fourier transform infrared (FT-IR), nuclear magnetic resonance (NMR), thermo gravimetric analysis (TGA), differential scanning calorimetry (DSC), zeta-nanosizer and dynamic light scattering (DLS) respectively, to state the effect of anion on the extended cellulose dissolution capabilities of the synthesized RTILs under mild conditions. As a polysaccharide solvent, diethyl dimethyl ammonium phosphate (A1P) showed the extreme capability to extract 65 % of cellulose from biomass without any pretreatment for 30 min. The present study could be a significant step toward the synthesis of efficient RTILs and generating upgraded cellulose for Hi-tech engineered composites and energy concerns.

Zinc oxide (ZnO) has been proven to be highly effective in converting biomass into fine chemicals. It possesses several limitations, such as leaching in hydrothermal reactions and difficulty with regard to its recovery. Supporting ZnO on silica improves its recovery, stability and recyclability. In this study, we produced silica-supported ZnO by incipient wetness impregnation (IWI) method for the conversion of glucose into lactic acid. The presence of the ZnO provided active sites for isomerization to occur. The highest yield of lactic acid was 39.2% at 180 °C for 60 min. Prolonged reaction time and higher reaction temperature promoted further degradation of lactic acid into acetic acid. The yield of lactic acid decreased after the first cycle and decreased slightly for the nine consecutive cycles.

This article reviews enzymatic preparation of functional polysaccharide hydrogels by means of phosphorylase-catalyzed enzymatic polymerization. A first topic of this review deals with the synthesis of amylose-grafted polymeric materials and their formation of hydrogels, composed of abundant natural polymeric main-chains, such as chitosan, cellulose, xantham gum, carboxymethyl cellulose, and poly(γ-glutamic acid). Such synthesis was achieved by combining the phosphorylase-catalyzed enzymatic polymerization forming amylose with the appropriate chemical reaction (chemoenzymatic method). An amylose-grafted chitin nanofiber hyrogel was also prepared by the chemoenzymatic approach. As a second topic, the preparation of glycogen hydrogels by the phosphorylase-catalyzed enzymatic reactions was described. When the phosphorylase-catalyzed enzymatic polymerization from glycogen as a polymeric primer was carried out, followed by standing the reaction mixture at room temperature, a hydrogel was obtained. pH-Responsive amphoteric glycogen hydrogels were also fabricated by means of the successive phosphorylase-catalyzed enzymatic reactions.

Cellulose monolith with a hierarchically porous morphology was utilized as a novel solid support for enzyme immobilization. After a series of modifications, succinimidyl carbonate (SC)-activated cellulose monolith (SCCL monolith) was obtained and it was employed to immobilize a model enzyme (horseradish peroxidase, HRP) through covalent bonding. The HRP immobilization capacity on SCCL monolith was calculated as 21.0 mg/g. The thermal stability measurement illustrated that the immobilized HRP exhibited a largely improved thermal resistance compared to its free counterpart. The reusability of the immobilized HRP was investigated, and it could be reused at least 10 cycles without significant activity loss. Therefore, cellulose monolith is found to be an ideal solid support for enzyme immobilization.

In this work, we present the hydrogen selective gas separation properties of the track-etched poly (ethylene terephthalate) (PET) membranes, which were functionalized with a carboxylic group. Also, Palladium (Pd) nanoparticles of average diameter 5 nm were deposited for a various time on pore walls as well as on the surface of carboxylated membranes. Effect of Pd nanoparticles binding with the increase of deposition time on gas separation and selectivity was studied. For the study of surface morphology of these composite membranes and the confirmation of Pd nanoparticles binding on the surface as well as on pore walls is characterized by scanning electron microscopy (SEM). The gas permeability of carboxylated membrane with increasing Pd deposition timing for hydrogen (H 2 ), carbon dioxide (CO 2 ) and nitrogen (N 2 ) was examined. From the gas permeability data of H 2 , CO 2 and N 2 gasses, it was observed that these membranes have higher permeability for H 2 as compared with CO 2 and N 2 . Selectivity of H 2 /CO 2 and H 2 /N 2 improves with the increased Pd nanoparticles deposition time. These membranes have effective application in the field of hydrogen based fuel cell.

Starch is constituted of amylose and amylopectin. Debranching of amylopectin converts it into amylose thereby producing resistant starch which is known to be less digestible by the amylase. This study designed resistant starch using acid hydrolysis and heat-moisture treatment methods with native corn starch as the starting material. Both native and processed starches were subjected to Fourier transform infrared spectroscopy, X-ray diffractometry, differential scanning calorimetry and molecular weight analysis. They were nanospray-dried into nanoparticles with 5-fluorouracil as the drug of interest for colon cancer treatment. These nanoparticles were subjected to size, zeta potential, morphology, drug content and in vitro drug release analysis. Heat-moisture treatment of native corn starch enabled the formation of resistant starch through amylopectin debranching and molecular weight reduction thereby enhancing hydrogen bonding between the starch molecules at the amorphous phase and gelatinization capacity. The nanoparticles prepared from resistant starch demonstrated similar drug release as those of native starch in spite of the resistant starch had a lower molecular weight. The resistant starch is envisaged to be resistant to the digestive action of amylase in intestinal tract without the formed nanoparticles exhibiting excessively fast drug release in comparison to native starch. With reduced branching, it represents an ideal precursor for targeting ligand conjugation in design of oral colon-specific nanoparticulate drug carrier.

In the present study we are performing simulation of simple model of two patch colloidal particles undergoing irreversible diffusion limited cluster aggregation using patchy Brownian cluster dynamics. In addition to the irreversible aggregation of patches, the spheres are coupled with isotropic reversible aggregation through the Kern–Frenkel potential. Due to the presence of anisotropic and isotropic potential we have also defined three different kinds of clusters formed due to anisotropic potential and isotropic potential only as well as both the potentials together. We have investigated the effect of patch size on self-assembly under different solvent qualities for various volume fractions. We will show that at low volume fractions during aggregation process, we end up in a chain conformation for smaller patch size while in a globular conformation for bigger patch size. We also observed a chain to bundle transformation depending on the attractive interaction strength between the chains or in other words depending on the quality of the solvent. We will also show that bundling process is very similar to nucleation and growth phenomena observed in colloidal system with short range attraction. We have also studied the bond angle distribution for this system, where for small patches only two angles are more probable indicating chain formation, while for bundling at very low volume fraction a tail is developed in the distribution. While for the case of higher patch angle this distribution is broad compared to the case of low patch angles showing we have a more globular conformation. We are also proposing a model for the formation of bundles which are similar to amyloid fibers using two patch colloidal particles.