Vinyl aniline modified cyclohexanone formaldehyde resins

The hydrothermal synthesis of zinc oxide (ZnO) particles from zinc acetylacetonate monohydrate in "pure" aqueous solution and in aqueous NaOH solution at 90 °C is reported. The structural and morphological properties of ZnO particles were investigated by powder X-ray diffraction, X-ray absorption spectroscopy (XAS), field emission scanning electron microscopy, and transmission electron microscopy. The effect of NaOH on the growth mechanism and photocatalytic performance of hierarchical ZnO structures was investigated. The experimental findings, supported by results of quantum chemical calculations at the level of density functional theory, were used to propose the mechanism of nucleation and preferential growth of finely tuned hollow and nonhollow ZnO structures and their effects on the photocatalytic activity. The calculations indicate that the process of ZnO nucleation in "pure" aqueous solution mainly proceeds by the reaction of small monomers, while tetramers play a crucial role in aqueous NaOH solution. Both the preferred ZnO nanostructure and microstructure growth processes are driven by O-H···O hydrogen bonds as controlling elements. The calculated values of the EO···H interaction indicate a stronger interaction via O-H···O hydrogen bonds in "pure" aqueous media (EO···H = -11.73 kcal mol-1) compared to those obtained in aqueous NaOH solution (EO···H = -8.41 kcal mol-1). The specific structural motif of the (ZnO-H2O)12 dodecamers with calculated negative ΔG*INT free release energy indicates that the formation of anisotropic nanocrystalline ZnO with the c-axis as the primary growth direction is spontaneous and accelerated exclusively in "pure" aqueous solution, whereas it is an unfavorable endergonic process in aqueous NaOH solution (ΔG*INT > 0). Efforts have been made to determine the photocatalytic efficiency of the ZnO samples based on the XAS measurements. ZnO particles obtained in "pure" aqueous solution show the highest photocatalytic activity due to the presence of a larger amount of oxygen vacancies.

Synthetic polymer single-chain nanoparticles (SCNPs) are an emerging new class of nanomaterials that possess similar folded structures as natural proteins. However, most SCNPs reported so far are p...

A method for lignin isolation from softwood based on complete dissolution in NaOH aqueous solution and liquid-liquid extraction was introduced. The structural features of milled alkali-soluble lignin (MAL) were comparatively analyzed with those of classical milled wood lignin (MWL) by means of alkaline nitrobenzene oxidation (NBO) and molecular weight, as well as Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectra analyses. The results showed that the yield of crude MAL (34.2%) was about twice as much as that of MWL (16.4%). The NBO product yields of MWL and MAL were quite similar. The weight-average molecular weight of MAL (10,400 g mol-1) was much higher than for MWL (6,970 g mol-1). Both MWL and MAL displayed similar FTIR, UV, 1H NMR, and 1H-13C HSQC NMR spectra. The total OH content of MAL (4.48 mmol g-1) was higher than that of MWL (3.89 mmol g-1). Compared with MWL, MAL showed similar structural characteristics but better isolation yield and higher molecular weight.

Sulfoethylation of polysaccharides—A comparative study

The solubilities of sodium p-toluenesulfonate (NaPTS), sodium sulfite (Na2SO3), and sodium p-methylphenoxide (NaCRS) in aqueous NaOH solutions and Na2SO3 in aqueous ethanol solutions were investigated using a dynamic method over the temperature range from 277 to 341 K at atmospheric pressure. The experimental results showed that the solubilities of NaPTS, Na2SO3, and NaCRS in aqueous NaOH solutions and Na2SO3 in aqueous ethanol solutions decreased distinctly with the solute-free mass fraction of NaOH (w40) and ethanol (w50). Further, there were obvious transition points in the solubility–temperature curves of NaPTS and Na2SO3 in aqueous NaOH solutions, and the transition points shifted to lower temperature as w40 rose. The forming of transition point was due to the different equilibrium solid phase, which was revealed by characterization of the equilibrium solid phase. But the transition points in the solubility–temperature curves of Na2SO3 in aqueous ethanol solutions remained constant at different w50 v...

Horseradish peroxidase-, hematin- and pegylated-hematin mediated polymerization of sodium styrene sulfonate and sodium acrylate in water is reported. Molecular weight and yields were influenced by the concentrations of hydrogen peroxide and initiator, 2,4-pentanedione. Hematin and pegylated-hematin were studied in lieu of peroxidase at pH 11.0 and 7.0 in aqueous solution, respectively. Polymer with a high molecular weight (Mn = 223,520) was formed when the pegylated-hematin was used as the catalyst. The results demonstrate vinyl polymerizations in an all aqueous process in high yield and molecular weight catalyzed by peroxidase as well as biomimetic catalysts.

The two hemicellulosic fractions were subsequentially extracted with 5% and 8% NaOH aqueous solution at a solid to liquid ratio of 1:25 (g mL(-1)) at 50 degrees C for 3 h from the water, 1 and 3% NaOH-treated sugar cane bagasse, and subfractionated into six preparations by a graded ethanol precipitation method at concentrations of 15%, 30% and 60% (v/v). Sugar composition and molecular weight analysis showed that, with an increasing concentration of ethanol, hemicellulosic subfractions with both higher Ara/Xyl ratios and higher molecular weights were obtained. In other words, with an increasing ethanol concentration from 15% to 60%, the Ara/Xyl ratios increased from 0.043 in H(1) to 0.088 in H(3) and from 0.040 in H(4) to 0.088 in H(6), and the weight-average molecular weights of hemicellulosic subfractions increased from 42 430 (H(1)) to 85 510 (H(3)) g mol(-1) and from 46 130 (H(4)) to 64 070 (H(6)) g mol(-1), respectively. The results obtained by the analysis of Fourier transform infrared, sugar composition, and (1)H and (13)C nuclear magnetic spectroscopy showed that the alkali-soluble hemicelluloses had a backbone of xylose residues with a beta-(1-->4)-linkage and were branched mainly through arabinofuranosyl units at C-2 and/or C-3 of the main chain, whereas the differences may occur in the distribution of branches along the xylan backbone.

To investigate the effects of NaOH and ethanol on the solubility of disodium decanedioate in water, the solubilities of disodium decanedioate in two aqueous solutions (aqueous NaOH solutions and aqueous ethanol solutions) were determined in a temperature range of (284 to 345) K. The solute-free mole fraction of NaOH and ethanol in the solvent mixtures extended from 0 to 0.084 and 0 to 0.472, respectively. With the increase of the mole fractions of ethanol (or NaOH) in solvent mixtures, the solubilities decreased obviously. Alcohol-out and alkali-out phenomena could be evidently observed, between which the alkali-out effect was more prominent. The determined data were correlated with the new electrolyte nonrandom two-liquid (E-NRTL) model, and the root-mean-square deviations of solubility temperature varied from (0.26 to 0.91) K.

A natural adhesive of starch (corn) that can be used to make and repair paper crafts was manufactured. The purpose of this study was to explore a composition of an adhesive having maximum adhesive strength while controlling a catalyst, a reaction initiator, and an oxidizing agent added to an aqueous starch solution at room temperature. The best composition was when a 35% starch aqueous solution was used. The 2.0% NaOH aqueous solution was added to the 35% starch aqueous solution to adjust pH from 10.0 to 11.0, and 0.20 g NiSO4, 20.0 g NaOCl, 30.0 g of 30.0% NaOH solution, and 3.0 g of 1.0% sodium thiosulfate were sequentially added. In the last step, the 3.0% HCl aqueous solution was added to adjust the pH of the adhesive to 7.5, and the adhesive strength of the prepared adhesive was 213 kgf/㎠. It was stable at room temperature for more than 60 days without physical changes such as viscosity, phase separation, precipitation, etc. In addition, TVOC, HCHO, and heavy metals were not detected, and the excellent result was found in antibacterial and reversible tests. This adhesive is an excellent natural adhesive that can be easily used by the user and does not contain harmful substances. It was an adhesive that could maintain the reputation of traditional materials in addition to their production and preservation.

An analysis is made of the kinetic characteristics of the hydrogenation of 4-nitro- and 2-nitro-2'-hydroxy-5'-methylazobenzenes, 4-nitroaniline and 4-aminoazobenzene over skeletal nickel in neutral azeotropic 2-propanol–water mixture and in the same solvent in the presence of acetic acid or sodium hydroxide. It is found that the selectivity of the hydrogenation of these isomers to the intermediate products depends on the composition and nature of the solvent, and is determined by the rate of reactive group conversion. Compared to the process in the presence of sodium hydroxide, which suppresses the route leading to the predominant hydrogenation of the nitro group, the contribution from the transformation of azo group is considerably greater in the hydrogenation of 4-nitro-2'-hydroxy-5'-methylazobenzene in the presence of acetic acid. Adding a base to the solvent during the hydrogenation of 2-nitro-2'-hydroxy-5'-methylazobenzene accelerates the rate of nitro group conversion and the intramolecular cyclization of the intermediate compound, increasing the selectivity towards the products containing the benzotriazole cycle (particularly 2-(2-hydroxy-5-methylphenyl)benzotriazole-N-oxide). The almost linear correlation between the selectivity of the catalytic hydrogenation of isomers of nitro-2'-hydroxy-5'-methylazobenzene and the kinetic characteristics of the hydrogenation of nitro and azo groups in compounds containing a single reactive substituent at different values of medium’s pH is estimated.

A novel cellulose solvent, 1.5 M NaOH/0.65 M thiourea aqueous solution, was used to dissolve cotton linters having a molecular weight of 10.1 × 104 to prepare cellulose solution. Regenerated cellulose (RC) films were obtained from the cellulose solution by coagulating with sulfuric acid (H2SO4) aqueous solution with a concentration from 2 to 30 wt %. Solubility of cellulose, structure, and mechanical properties of the RC films were examined by infrared spectroscopy, X‐ray diffraction, scanning electron microscopy, 13C NMR, and tensile tests. 13C NMR analysis indicated that the novel solvent of cellulose is a nonderivative aqueous solution system. The presence of thiourea enhanced significantly the solubility of cellulose in NaOH aqueous solution and reduced the formation of cellulose gel; as a result, thiourea prevented the association between cellulose molecules, leading to the solvation of cellulose. The RC film obtained by coagulating with 5 wt % H2SO4 aqueous solution for 5 min exhibited higher mechanical properties than that with other H2SO4 concentrations and a homogenous porous structure with a mean pore size of 186 nm for free surface in the wet state. The RC film plasticized with 10% glycerin for 5 min had a tensile strength of 107 MPa and breaking elongation of 10%, and about 1% glycerin in the RC film plays an important role in the enhancement of the mechanical properties. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1521–1529, 2002

Effect of molecular weight and pH on the self-assembly microstructural and emulsification of amphiphilic sodium alginate colloid particles

Effects of polydimethylsiloxane (PDMS) molecular weight on performance of PDMS/ceramic composite membranes

Preferential growth of nickel hydroxide through the controlled release of base from acrylamide-crotonic acid hydrogels

We report the ultrastiff and tough poly(acrylamide- co-acrylic acid)/Na-alginate/Fe3+ (P(AM- co-AA)/Na-alginate/Fe3+) hydrogel via the formation of hybrid ionic-hydrogen bond cross-linking networks. The optimal P(AM- co-AA)/Na-alginate/Fe3+ hydrogel possessed super high elastic modulus (∼24.6 MPa), tensile strength (∼10.4 MPa), compression strength (∼44 MPa), and toughness (∼4800 J/m2). The P(AM- co-AA)/Na-alginate/Fe3+ hydrogel was highly stable and maintained its superior mechanical properties in 0.5-2 M NaCl solution, aqueous solution with pH ranging from 4 to 10. The ionic cross-linking networks of the P(AM- co-AA)/Na-alginate/Fe3+ hydrogels can be locally and selectively dissociated by treating with aqueous NaOH solution with pH of 13 for 1 min and reformed by locally adding the additional Fe3+ solutions, making the hydrogels healable and cohesive. The healed hydrogels from the cutting surfaces can bear a tensile strength of up to 7.1 MPa. Various complex hydrogel structures can be constructed by using the P(AM- co-AA)/Na-alginate/Fe3+ hydrogels as building blocks via the adhesion of as-prepared hydrogels.