Образцы трис-цис-трис-транс-додекафенилциклододекасилоксандодекаола (додекаол) с различной кристаллической структурой были исследованы с помощью методов ТГА и РСА. Было установлено, что эти образцы проявляют мезоморфные свойства. Их температурное поведение и тип образуемых ими мезофаз напрямую связаны с типом Н-связанных макроциклосилоксановых фрагментов, формирующих исходную кристаллическую структуру. В свою очередь, тип упорядочения мезофазы определяет структуру конечных продуктов поликонденсации. Показано, что полифункциональный макроциклический силоксановый додекаол может быть использован как мономер для получения ковалентно связанного «двутяжевого листового полимера».

The molecular order and thermotropic transitions of tris-cis-tris-trans-dodeca[organo(dimethylorganosiloxy)]cyclododecasiloxanes {RSi(O) [OSiMe2R']}(12) (R = Ph, R' = Me, CH2Cl, Vi; R = Me, Et, Vi, R' = Me) have been investigated using differential scanning calorimetry, thermogravimetric analysis, and X-ray scattering. The cyclododecasiloxanes with phenyl side groups (R = Ph) can form mesomorphic structures within a very wide temperature range. Compounds with R = Me and Vi are liquids and exhibit microphase separation above their glass transition temperature because of the different nature and structure of the organic R and trimethylsiloxy OSiMe3 side groups. When the side group R = Et, a mesomorphic structure is formed in a substantially more narrow temperature region than that for cycles containing phenyl groups. Thus, the type of side group R in organocyclododecasiloxanes determines their ability for self-ordering into mesomorphic structures and the thermal stability of the mesomorphic state.

Highly concentrated solutions of cellulose and solutions of cellulose blends with synthetic polymers are prepared via the solid-phase dissolution of cellulose in N-methylmorpholine-N-oxide. The phase state and morphological features of these solutions are studied via DSC and polarization microscopy, and their rheological behavior is considered. Evolution in the structure of cellulose in these systems is investigated at all stages during spinning of oriented fibers from solutions. It is first shown that the addition of synthetic polymers to cellulose makes it possible to control processes of cellulose structuring; to stop them at the stage of mesophase formation; and, thus, to avoid further perfection of the structure and formation of the crystalline phase of cellulose.

Noncovalent columnar polymers (NCPs) based on cyclodextrins (CD) are polymeric assemblies of molecules that have continuous hollow channels, the width of which is determined by the diameter of the cavity of the initial CDs. The repeating fragment in an NCP is the CD molecule. For NCPs that were obtained by the exclusion of polymer backbone macromolecule from the corresponding inclusion complexes (ICs) based on β-cyclodextrin (NCPexcl), the polymer length, expressed as the number of macrocycles in a single chain (n) is determined by the size of the included ligand, polypropylene glycol (PPG), and is the PPG polymerization degree divided by two. The determination of the molecular weight of an NCP obtained by the precipitation method (NCPprec) is rather difficult, since they are present in the aggregated state rather than in the form of individual molecules in solution. To estimate the molecular weight of NCPprec, an indirect method is used, which is based on the determination of the aggregation rate of the ICs formed as a result of the interaction between an NCP and polypropylene glycol with a fixed molecular weight (MW), in this case PPG 1000. The comparison of the aggregation rates of the inclusion between NCPexcb (which were synthesized using PPGs with different molecular weights) and PPG 1000 with the aggregation rate of the inclusion complex on the basis of NCPprec provided the estimation for the MWs of single polymer chains. The fact that the samples of NCPprec contain ∼30% of the monomeric β-CD was taken into account when constructing the calibration curve. It was demonstrated that the MW of the polypropylene glycol corresponding to NCPprec is 1320 Da. Consequently, ∼11–12 molecules of β-CD are included in the single chains of NCPprec.

X-ray diffraction and TMA studies show that surfactant sodium alkyl sulfonate (C15) forms one of its two LC structures (distinguished by the smallest layer periodicity) in butadiene-nitrile elastomers containing different amounts of acrylonitrile units. In this case, the surfactant serves as a structural plasticizer and facilitates a more complete selective segregation of microblocks of trans-1,4-butadiene units and, especially, of sequences of alternating trans-1,4-butadiene and acrylonitrile units.

A columnar modification of β-cyclodextrin (β-CD col ) has been synthesized using self-assembly and self-organization processes. It is shown that the obtained macrocycle assemblies in the solid state are highly ordered structures with through cylindrical pores with an average diameter of ∼0.7 nm and a length of about 60 nm. These structures can be of interest as a new type of macroreceptors for the inclusion of molecules with diameters not exceeding 0.7 nm belonging to various chemical classes. The abilities of the common cage structure of β-CD and the β-CD col modification to bind low-molecular-weight volatile organic compounds have been compared. The dependence of the composition, structure, and thermal stability of the inclusion complexes on the ligand nature and geometry is analyzed. The absence of any specificity in the adsorption of ligands on β-CD col and the possibility of using this structure as a stable nanocontainter for the storage of volatile compounds is demonstrated.

A comparative analysis of the ozone resistance of vulcanizates based on butadiene-nitrile elastomers with the same network density but different contents of acrylonitrile units is performed. The role of the orientation of chain fragments of vulcanizate chains during the reaction of double bonds with ozone is demonstrated.

На основе концепции твердофазного растворения целлюлозы в N-метилморфолин-N-оксиде получены высококонцентрированные целлюлозные растворы и смесевые растворы целлюлозы с синтетическими полимерами. Методами ДСК и поляризационной микроскопии исследованы фазовое состояние и морфологические особенности полученных растворов. Рассмотрены их реологические свойства. Исследована эволюция структуры целлюлозы в этих системах на всех стадиях процесса формования ориентированных волокон из растворов. Впервые установлено, что введение синтетических полимеров в целлюлозу позволяет регулировать процессы структурообразования целлюлозы, приостанавливая их на стадии образования мезофазы и тем самым исключая дальнейшее совершенствование структуры и формирование кристаллической фазы целлюлозы.

Kinetic analysis of the aggregation of complexes formed by columnar types of α- and γ-cyclodextrins (α-CDcol and γ-CDcol) and poly(alkylene glycols) is performed by the dynamic light scattering method. For comparison, analogous studies were conducted for systems containing initial α- and γ-cyclodextrins (α-CD and γ-CD). Upon the aggregation of systems containing α-CD, the number of nuclei with critical sizes slowly increases at the initial part of kinetic curve throughout the solution bulk; when some limiting concentration and sizes of formed aggregates are achieved, the system is transformed into the gel-like state. The aggregation of γ-CDcol-poly(ethylene glycol) system proceeds into two stages. At the first fast stage, aggregates are formed by particles representing single-strand inclusion complexes composed of one γ-CDcol molecule and two units of ethylene oxide. At the second, much slower stage, aggregates are formed by two-strand complexes composed of one γ-CDcol molecule and four units of ethylene oxide. It follows from the comparison of aggregative properties of γ-CDcol-poly(ethylene glycol) and γ-CDcol-poly(propylene glycol) systems that the rate of aggregation is much higher in the second case.

The phase behavior and structure of liquid-crystalline phases of three series of copolymers with mesogenic units belonging to the families of biphenyls and phenyl benzoates have been studied, with the former mesogenic units containing a chiral center in a flexible spacer. A variation in the isotropization temperature as a function of composition is well described by the additivity rule, whereas the tilt angle of mesogenic groups in smectic layers changes nonlinearly. This angle decreases beginning from homopolymers and attains the minimum value for the copolymers of the equimolar composition, which show the highest ferroelectric activity among the polymer systems under study.

A hydrolytic condensation of methyltriethoxysilane was performed in the presence of sodium and copper ions. A crystalline copper/sodium-methylsiloxane of a general formula {Na-4[(MeSi(O) O)(12)Cu-4]} center dot 6(n-BuOH) (1a) was obtained as the only product in a high yield. X-ray analysis of a single crystal obtained after recrystallization of 1a by slow diffusion of methanol vapours into its ethanol solution was characterised as {Na-4[(MeSi(O) O)(12)Cu-4]} center dot 4(MeOH) center dot 4(EtOH) (1b). In the crystal molecules are assembled into zig-zag chains by O-H H center dot center dot center dot O bonds. Removal of metal ions by a reaction of 1a or 1b with Me3SiCl gave a new siloxane macrocycle tris-cis-tris-trans-dodecamethyldodecatrimethylsiloxycyclododecasiloxane, [MeSi(O)OSiMe3](12) (2), in a high yield. (C) 2008 Elsevier B. V. All rights reserved.

Control over nanoparticle shape, liquid crystal (LC) polymer architecture, and the related mesophase structure has made possible the creation of new polymer/CdSe semiconductor nanoparticle composite materials. Surface modification of semiconductor quantum dot nanoparticles by hydrogen-bonded LC polymers resulted in the formation of uniform and coagulation-free bulk systems. The effect of the LC polymer on the alignment of nanoparticles within the composite was established by varying the polymer structure and the size of the quantum dots. The resultant composites represent a new class of nanomaterials in which quantum dots are aligned within the planes provided by the initial smectic layers separated by the periodically located polymer backbones.

A new method for the synthesis of associates of cyclodextrins (CDs) of the columnar type consisting of the precipitation of CDs from aqueous solutions into acetone at lowered temperatures is developed. It is shown that columnar structures exist in both a crystalline state and in aqueous solutions. Hydrodynamic radii and molecular masses of noncovalent columnar structures (NCSs) in aqueous solutions are determined by the dynamic and static light scattering methods. The degree of association of noncovalent columnar polymers is ∼40. It is revealed the NCS associates based on β-CD are stable and their hydrodynamic radius R h is equal to 100 ± 10 nm. The kinetics of interactions of initial β-CD and NCS with poly(propylene oxide) (PPO) is studied. The pattern of kinetic curves of R h growth upon interaction between NCS and PPO indicates that the aggregation of the particles of polymer inclusion complex proceeds in the regime of reaction-limited cluster-cluster aggregation. Kinetic curves describing the interaction processes between β-cyclodextrin and PPO are characterized by the presence of induction period t 0 . At t > t 0 , R h ∞ t 0.56 which is typical for the diffusion-limited cluster-cluster aggregation. Schemes of the formation of polymer inclusion complexes between initial β-CD or NCS and poly(propylene oxide) are proposed. Comparison of kinetic data on the complexation of β-CD in solution in the form of associates of two types with PPO demonstrates that columnar forms of associates are reactive species acting as macroreceptors.

The dissolution of thermotropic alkylenearomatic LC copolyesters and isotropic poly( m -phenyleneisophthalamide) in a high-polarity donor solvent, N -methylmorpholine- N -oxide, has been studied. It has been demonstrated that N -methylmorpholine- N -oxide shows high dissolving power with respect to hydrophobic synthetic polymers. In this case, the dissolution of the polymers is accompanied by the formation of crystal solvates of different compositions. With the use of polarization microscopy, DSC, and X-ray diffraction, the stages of formation of crystal solvates have been examined and the phase equilibrium in systems containing crystal solvates has been investigated. Special attention is given to the structural and morphological features of such heterophase systems.