Formation of porous matrices from lactide and ε-caprolactone copolymers in supercritical carbon dioxide medium

A series of lactide and ε-caprolactone copolymers containing 4–24 mol % of ε-caprolactone with 20- to 30-kDa molecular weights are synthesized. Based on them, porous materials are produced by foaming in supercritical carbon dioxide. The pore size was shown to decrease with increasing ε-caprolactone content in copolymer, while the porosity of the entire sample was not altered. The resulting pore size also decreases if 7 wt % polyethylene glycol is added to the initial monomer mixture. The Young’s modulus of the porous samples decreases with increasing ε-caprolactone content and when polyethylene glycol is added.     

Structure and properties of new dicationic ionic liquid DBTMEDA(BF4)2

Structural Chemistry - Dicationic ionic liquid (IL) dibutyltetramethylethylenediammonium tetrafluoridoborate was synthesized for the first time by quaternization followed by ion exchange. The...     

Foreword

Structural Chemistry - Milestones of historical evolution of the Chemistry Department of the Lomonosov Moscow State University, which was formally separated from the physical-mathematical faculty...     

Influence of heat treatment on the size of sodium lignosulfonate particles in water—ethanol media

Russian Chemical Bulletin - Dynamic light scattering and size exclusion chromatography were used to investigate the size of sodium lignosulfonate particles in water—ethanol media and the...     

Dynamics of Lignin Destruction in Pine Wood under the Action of Ozone

Russian Journal of Physical Chemistry A - The destruction of lignin in pinewood during ozonization is studied via diffuse reflection IR spectroscopy (DRIFT) and Raman spectroscopy. The DRIFT...     

Adsorption of Methylene Blue on Lignocellulosic Plant Materials

Russian Journal of Physical Chemistry A - A comparative study of the sorption properties of lignocellulosic plant materials (aspen and pine wood and wheat straw) is performed using the cationic dye...     

Carboxylated and decarboxylated nanotubes studied by X-ray photoelectron spectroscopy

Carbon nanotubes (CNTs) of the conic and cylindrical structure were studied by X-ray photoelectron spectroscopy in the initial state and after carboxylation and decarboxylation reactions. The O=C—O and C—O groups were revealed on the surface of the chemically modified samples. It was found that both the carboxylated and decarboxylated cylindrical CNTs contain a smaller amount of oxygen than the corresponding conic CNTs apparently due to differences in their structures.     

Delignification of deciduous wood under the action of hydrogen peroxide and ozone

Kinetic curves of the dependence of ozone specific absorption (Q _{r, sp} ) upon the ozonation of aspen wood pretreated with solutions of hydrogen peroxide of various concentrations (from 5 × 10^?4 to 2 × 10^?1 mol/L) are obtained. The water content in the samples being 56 ± 3%. The initial rate of ozone absorption and total ozone consumption (Q _inlet) are determined. Wood samples are investigated by IR and UV diffuse reflection spectroscopy. Based on the kinetics and spectral data, it is concluded that pretreating wood with a H₂O₂ solution allows the degree of delignification (DD) to be increased at a constant Q _inlet value. The DD is maximal at $ C_{H_2 O_2 } = 5 \times 10^{ - 3} $ mol/L and is 88% in contrast to a sample ozonated without H₂O₂ (DD = 85%). The role of pretreatment with hydrogen peroxide and the subsequent action of the O₃/H₂O₂ system in the process of delignification of wood is analyzed.     

Transformation of wood during ozonization in the presence of hydrogen peroxide

Samples of ozonized aspen wood pretreated with hydrogen peroxide solutions of various concentrations are investigated by UV diffuse reflectance spectroscopy, IR spectroscopy, and X-ray structural analysis. The general course of wood transformation under the action of the O₃/H₂O₂ system is associated with the destruction of lignin and oxidation of carbohydrates, raising the fraction of the crystalline phase in a lignocarbohydrate material. The possibility of varying the depth of the chemical and structural transformation of the substrate upon changing the hydrogen peroxide concentration in the O₃/H₂O₂ system is demonstrated.     

Fullerides: heterometallic superconductors with composition M<Subscript>2</Subscript>M′C<Subscript>60</Subscript> (M = K,Rb; M′ = Yb,Lu, Sc)

One- or two-step reactions of potassium and rubidium fullerides with composition M_k C₆₀ (M = K, Rb; k = 3—6) and K₆C₆₀ + m K mixtures (m = 1, 3) with anhydrous salts MCl₃ (M = La, Pr, Nd, Sm, Gd, Tb, Yb, Lu, Y, Sc) and YbI₂ in a toluene—THF medium afforded heterometallic fullerides M_3–nM_nC₆₀ (n = 1—3). Among these compounds, substituted fullerides with composition M₂MC₆₀ (M = Yb, Lu, Sc) display superconducting properties with critical temperatures of 14—20 K.Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1623–1628, August, 2004.