Universal Character of Breaking of Wormlike Surfactant Micelles by Additives of Different Hydrophobicity

Wormlike surfactant micelles are widely used in various applications including fracturing technology in oil industry, template synthesis of different nanoobjects, micellar copolymerization of hydrophilic and hydrophobic monomers, and so forth. Most of those applications suggest the solubilization of different additives in the micelles. The present paper is aimed at the comparative study of the effect of the solubilization of hydrophobic (n-decane and 1-phenylhexane) and hydrophilic (N-isopropylacrylamide and acrylamide) substances on the rheological properties and structure of the micelles using several complementary techniques including rheometry, small angle neutron scattering, dynamic light scattering, and diffusion ordered NMR spectroscopy. For these studies, mixed micelles of potassium oleate and n-octyltrimethylammonium bromide containing the excess of either anionic or cationic surfactants were used. It was shown that hydrophobic additives are completely solubilized inside the micelles being localized deep in the core (n-decane, 1-phenylhexane) or near the core/corona interface (1-phenylhexane). At the same time, only a small fraction of hydrophilic additives (14% of N-isopropylacrylamide and 4% of acrylamide) penetrate the micelles being localized at the corona area. Despite different localization of the additives inside the micelles, all of them induce the breaking of wormlike micelles with the formation of either ellipsoidal microemulsion droplets (in the case of hydrophobic additives) or ellipsoidal surfactant micelles (in the case of hydrophilic additives). The breaking of micelles results in the drop of viscosity of the solution up to water value. The main result of this paper consists in the observation of the fact that for all the additives under study, the dependences of the viscosity on the volume fraction of additive lie on the same master curve being shifted along the volume fraction axis by a certain factor depending on the hydrophobicity of the added species. Those data are quite useful for various applications of wormlike surfactant micelles suggesting the solubilization of different additives inside them

Synthesis, Structure and Electrochemical Properties of Acetamide- and Caprolactam-Containing Silicon Catecholates

Hexacoordinated heteroligand silicon catecholates, although being prospective as easily soluble compounds with high hydrolytic stability and diverse redox properties, have been insufficiently studied. The transesterification of 1-(trimethoxysilylmethyl)-2-oxohexahydroaze or N-methyl-N-(trimethoxysilylmethyl)acetamide by two equivalents of catechol derivatives in the presence of dicyclohexylamine afforded a series of target compounds in good yield. The complexes were characterized using elemental analysis, FTIR, 1H, 13C and 29Si NMR spectra, X-ray crystallography and cyclic voltammetry. X-ray diffraction confirmed that the silicon atom possesses the octahedral geometry of the SiCO5 polyhedron that remains unchanged in solution as it follows from 29Si NMR data. The compounds demonstrated up to three oxidation waves; and the reduction profile strongly depended on the nature of the substituents on a catecholate anion

Дерматологическая токсичность высоких доз тиотепы у детей. Описание клинического случая

Hematopoietic stem cell transplantation (HSCT) is a treatment modality for a number of severe malignant and non-neoplastic diseases. Autologous hematopoietic stem cell transplantation (auto-HSCT) improves outcomes in patients with solid and hematological malignancies. Skin lesions at the auto-HSCT stage are quite common and represent an important diagnostic and therapeutic problem. The most significant causes of skin lesions in auto-HSCT are drug toxicity, infectious and viral lesions. Each of the complications can manifest itself to varying degrees as well as combine with others, having a significant negative on the patient’s condition, posing a threat to the patient’s life in severe cases.Трансплантация гемопоэтических стволовых клеток (ТГСК) является методом терапии ряда тяжелых злокачественных и неопухолевых заболеваний. Аутологичная трансплантация гемопоэтических стволовых клеток (ауто-ТГСК) улучшает исходы у пациентов со злокачественными новообразованиями солидной и гематологической природы. Поражения кожи на этапе ауто-ТГСК встречаются достаточно часто и представляют собой важную диагностическую и терапевтическую проблему. Наиболее значимыми причинами поражений кожи при ауто-ТГСК являются медикаментозная токсичность, инфекционные и вирусные поражения. Каждое из осложнений может проявляться в различной степени, а также сочетаться с другими, оказывая значимое отрицательное влияние на состояние пациента, в тяжелых случаях представляя угрозу для жизни пациента