Prediction of multicomponent liquid adsorption using excess quantities I. Statistical thermodynamic derivation of the basic equation of excess formalism

The utilization of excess quantities as the basis of a thermodynamic approach can simplify the prediction of multicomponent liquid adsorption from binary data. From statistical thermodynamics, the fundamental equation is derived for the prediction of ternary or higher order data from adsorption data for the constituent binary mixtures. An additive expression is obtained for the double Gibbs free excess energies, valid for adsorption on liquid mixture/air interfaces as well as liquid mixture/solid interfaces.     

Polymer nanocomposites with “ultralow” refractive index

Nanocomposites of gelatine and gold were prepared by reduction of AuCl₄H in a gelatine solution, followed by a spin coating process and a brief washing. The thickness of the films thus obtained was typically 200–400 nm. The surface of the nanocomposites was investigated by scanning electron microscopy (SEM) and surface profilometry. The size of the gold particles is in the range of ca. 2–10 nm, as elucidated by transmission electron microscopy (TEM). Refractive indices were measured by ellipsometry at wavelengths of 632.8 and 1300 nm. The refractive index depends linearly on the volume fraction of gold, at least at 1300 nm. The lowest refractive indices measured are 1.008±0.060 at 1300 nm and 0.963±0.062 at 632.8 nm (limits are 95% confidence interval). These values are, to our best knowledge, the lowest reported for a polymer or polymer composite.     

Formation of a transient periodic stripe domain pattern in nematic AB block copolymer solution during photo-induced director reorientation

A transient periodic stripe domain pattern is observed during photo-induced director reorientation of a sample containing rod-like block copolymer vesicles in a low molecular weight nematic liquid crystal.     

Application of various ionic liquids as cosolvents for chloroperoxidase-catalysed biotransformations

Abstract  

Chloroperoxidase from Caldariomyces fumago catalyses oxidation of indole and thioanisole in reaction mixtures containing up to 40% (v/v) of different ionic liquids (ILs). Results indicate that ILs containing tosylate, trifluoroacetate, chloride, and methylsulfate anions are suitable cosolvents for these transformations, yielding high enantiomeric excess and good conversion rates.     

染料敏化太阳能电池用TiO2薄膜电极的改性制备及光电化学性能

以钛酸四异丙酯为钛源, 用水热法合成制备了具有典型锐钛矿晶型的TiO2纳米材料. 采用金属镍掺杂和表面包覆一层氧化钕, 对TiO2薄膜电极进行改性研究. 实验结果表明, 所制备纳米TiO2颗粒较均匀, 粒径约为17~18 nm. 经镍掺杂后, 颗粒团聚粒径明显增大, 但是仍保持均匀状态和多孔结构. 与改性前的TiO2薄膜电极相比, 金属掺杂和表面包覆有助于光生电子和空穴有效地分离, 电池的短路光电流提高了16%, 光电转换效率提高了17%.     

Rheological and Rheo-Optical Investigation of Cellulose Ethers in Aqueous Solution

The opportunities provided by rheo-optical techniques for the investigation of cellulose derivatives in solution are discussed. Flow birefringence experiments yield information on the optical properties of the material and allow to distinguish between the contribution of different structural elements like, for example, the dangling chains and the anisotropic stem of fringed micelles on shear thinning and flow orientation, respectively. Rheo-turbidity and rheo-small angle light scattering measurements were used to study the influence of shear on the phase separation that occurs in aqueous methyl hydroxypropyl cellulose (MHPC) solutions upon heating. Both shear induced mixing and demixing were found and also differences between temperature ramp and shear rate ramp experiments were observed. The differences between chemical and physical crosslinking of MHPC were characterized by low amplitude oscillatory shear measurements. Finally, the possibility to prepare microgels by shearing the samples during the crosslinking reaction is reported.     

Critical behavior of trifunctional randomly branched polycyanurates

The behavior near the gelation threshold of trifunctional randomly branched polycyanurates is studied by static and dynamic light scattering. By static measurements the critical exponents γ, σ and η were obtained, which describe the divergence of the weight average (M_w) and the cutoff (M*) molecular weights and the radius of gyration (R_g) respectively. All these independently measured exponents together with τ, characterizing the power law behavior of the molecular weight distribution and measured by size exclusion chromatography coupled with light scattering, confirm the predictions of the three-dimensional percolation theory. With the help of size exclusion chromatography coupled with a light scattering and a viscosity detector, a fractal dimension D = 2.24 is obtained. On the other side, from the corresponding exponent for the whole unfractionated samples a fractal dimension D = 2.21 results, using a theory of Daoud. This suggests that the fractal dimension of the polycyanurates in dilute solution lies between the theoretical predictions D = 2.5 for the unswollen and D = 2.0 for the completely swollen state. Furthermore, it is shown by dynamic light scattering that the power law behavior over some decades in time of the time autocorrelation function and the divergence of the mean relaxation time are characteristics of the gelpoint. The development with increasing reaction time of the time correlation function of the gelling system from the pregel through the gelpoint into the gel state is analyzed quantitatively by a hybrid of a stretched exponential and a power law function.     

How trifluoroacetone interacts with water

The rotational spectra of five isotopologues of the molecular adduct 1,1,1-trifluoroacetone-water have been assigned using pulsed-jet Fourier-transform microwave spectroscopy. All rotational transitions appear as doublets, due to the internal rotation of the methyl group. Analysis of the tunneling splittings allows one to determine accurately the height of the 3-fold barrier to internal rotation of the methyl group and its orientation, leading to V(3) = 3.29 kJ·mol(-1) and ∠(a,i) = 67.5°, respectively. The water molecule is linked to the keton molecule on the side of the methyl group through a O-H···O hydrogen bond and a C-H···O intermolecular contact, lying in the effective plane of symmetry of the complex.     

Internal dynamics in complexes of water with organic molecules. Details of the internal motions in tert-butylalcohol-water

The peculiar propensity of water to have a high internal dynamic activity in its molecular complexes with organic molecules is described in this paper. Often, the corresponding large amplitude motions are reflected in the tunnelling splittings of the rotational transitions which, in turn, provide information for the determination of the potential energy surfaces and of the noncovalent interactions of water with a variety of atoms and/or functional groups. A classification of this kind of molecular complexes is given, also in relation to the tunnelling features of the rotational spectra. As a specific example, the rotational spectrum of tert-butylalcohol-water, investigated by Fourier transform microwave spectroscopy, is reported. Details are given of the large amplitude motions which take place in the adduct, the internal rotation of the hydroxyl group and the oscillations of the water molecule, by interpreting the experimental data with a flexible model.