Synthesis of rodlike polysiloxane with hexagonal phase by sol-gel reaction of organotrialkoxysilane monomer containing two amino groups

A higher-ordered polysiloxane was prepared by the sol-gel reaction of (3-(2-aminoethylamino)propyl)trimethoxysilane in a hydrochloric acid aqueous solution without using any surfactants. The X-ray diffraction profile of the resulting polysiloxane showed three peaks with the d-value ratio of 1:1/√3:1/2, indicating that this polysiloxane has a hexagonal phase. The peaks shifted by changing the humidity. Therefore, we estimated that this hexagonal phase came from the stacking of a rodlike polymer with a Si-O-Si framework at the core and ammonium groups extruding outside. The TEM image of the polysiloxane showed a stripe pattern indicating an ordered arrangement. Because one repeating unit of the present polysiloxane has two ammonium groups, the ion-exchange capacity of this polysiloxane and viscosity of its aqueous solution were larger than those of the previous polysiloxane with single-ammonium group.     

热处理对化学镀钴磷薄膜组织结构和磁学性能的影响

化学镀钴磷薄膜具有优良的磁学性能。研究了不同的热处理条件下薄膜组织结构对磁学性能的影响。化学镀钴磷薄膜镀态下为单一的α－固溶体,矫产力和矩形比较高,具有磁各向异性。     

Long-Range Interactions in Thin Smectic Films on Substrates: X-Ray Reflectivity Studies

Long-range forces between interfaces of thin and ultrathin smectic films are responsible for their thickness and stability. We present here X-ray reflectivity studies of the forces in spin-coated thin films of three different commercial liquid crystal (LC) mixtures as well as in main-chain LC polymers based on polysiloxane. All these LC materials possess a smectic C* phase at room temperature. We demonstrate spontaneous molecular self-assembly after spin coating into a nearly perfect smectic layer structure on various substrates. However, annealing at room temperature is essential to achieve an equilibrium state. Measurements on ultrathin annealed films of the LC mixtures show dramatic variation of the smectic layer spacing, L, as a function of the number of smectic layers, n (or film thickness, d). The functional dependence of L(n) for all three different liquid crystal mixtures suggests a long-range interaction between the interfaces that decays algebraically as 1/n^κ where κ = 2 ± 0.3. This decay is consistent with a van der Waals type of interaction, although its magnitude cannot be explained by the existing mechanisms. X-ray studies of thick and thin annealed polysiloxane films allow determination of the phases, the phase transition temperatures, and the temperature dependence of the tilt angle in the smectic C* phase. Thin (300 Å to 600 Å) polysiloxane films far above the bulk smectic–isotropic phase transition temperature show the formation of smectic film at the film–substrate interface due to surface freezing phenomena. Preliminary investigations of the temperature dependence of the smectic film thickness indicate that the interaction between the interfaces decays algebraically, with an exponent κ = 1.5 ± 0.5.     

Polymorphism in a metallocenic isotactic polypropylene as revealed by means of FTIR spectroscopy: Influence of the processing conditions

The polymorphic structure in specimens of a metallocenic isotactic polypropylene, processed under different conditions, has been studied by means of wide‐angle X‐ray scattering (WAXS), differential scanning calorimetry (DSC), and Fourier transform infrared spectroscopy (FTIR). The proportions of the different polymorphs have been evaluated, and the influence of the processing parameters (nucleating agents, cooling rate, and nature of the surface of the molds) has been analyzed. The combination of WAXS, DSC, and FTIR results confirms the adequacy of this last technique to obtain quantitative information about the competition between the crystalline phases of polypropylene. It has also been proved that the nature of the mold can enhance considerably the activity of beta‐nucleating agents. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

II-I phase transformation of melt-crystallized oriented lamellae of polybutene-1 by shear deformation

Summary Modification II-I transformation of polybutene-1 was investigated on oriented lamellae, which were melt-crystallized in the temperature gradient. WAXS photograph of as-grown specimen showed prefered orientation of [110] to the lamellar axis, and after transformation it showed twelve point pattern due to dual orientation of hexagonal lattice. By shear deformation parallel or perpendicular to lamellar axis, WAXS photograph showed the appearance of six point pattern due to single orientation of hexagonal lattice, and also the enhancement of transformation rate. These were explained by the growth of hexagonal nuclei formed by the slip in the tetragonal crystal.     

Nanodiamonds as modifier of ethylene-1-octene copolymer structure and properties

The structure and stretching behavior of low density (0.86 g/cm³) ethylene-1-octene copolymer (EOC) modified with 0.015–1.44 vol.% (0.05–5 wt.%) of nanodiamonds (ND) particles were studied. Analysis of the structure of the EOC and nanocomposites by DSC, wide and small angle X-ray techniques revealed three phase structure in isotropic samples. In addition to the amorphous phase, there are two ordered phases: orthorhombic crystallites and hexagonal mesophase. ND particles display quite uniform distribution in EOC matrix up to 1.44 vol.%. The average size of ND particles is similar according to SAXS and WAXS data. It was found that introduction of ND particles into EOC matrix leads to the formation of the perfect orthorhombic phase crystallites, increases the rate of crystallization and crystallinity, resulting in increase in strength and Young modulus.     

Two-dimensional single-crystalline Zn hexagonal nanoplates: size-controllable synthesis and X-ray diffraction study

We synthesized two-dimensional (2D) Zn hexagonal nanoplates using the thermal metal-vapor deposition technique. An increase and decrease in the surface area and thickness of the 2D Zn hexagonal nanoplates were shown with elevated annealing temperatures, indicating their sizes to be controlled using the annealing treatment. X-Ray diffractometry (XRD) studies revealed the crystalline nature of the 2D Zn hexagonal nanoplates and the diffraction intensity of the (002) lattice plane, which increased parabolically with elevated annealing temperatures.     

Ordering effects on the photopolymerization of a lyotropic liquid crystal

The synthesis of polymers bearing the highly ordered nanostructure of lyotropic liquid crystal (LLC) phases has recently been of great interest. This work describes the polymerization behavior and structural evolution of a cationic amphiphile in various LLC phases. The type and degree of LLC phases formed from this monomer depend strongly on the composition and temperature. By adding a nonpolymerizable surfactant a variety of LLC phases are formed including hexagonal, bicontinuous cubic, and lamellar morphologies while maintaining a constant monomer concentration. The highly ordered lamellar LLC phase exhibits the fastest polymerization rate with the slowest occurring in the hexagonal phase. The polymerization rates of the bicontinuous morphology were intermediate to the lamellar and hexagonal phases. The faster polymerization kinetics is due to diffusional limitations imposed on the propagating polymer by the highly ordered lamellar LLC phase. Also, the order of this LLC system has a strong dependence on temperature. At higher temperatures, the degree of LLC order and correspondingly the polymerization rate decrease. The original LLC phase morphology appears to be retained to the greatest extent in the faster polymerizing lamellar phase. The original nanostructure is also retained in the hexagonal and cubic LLC phases but with some slight changes in structure. This LLC structure is preserved at temperatures well exceeding the thermal phase transitions of the unpolymerized LLC samples.     

Preparation and thermal characterisation of some new liquid crystalline copolymers involving a spacer unit based on vinylacetic acid

Summary Three series of new liquid crystalline (LC) copolymers having a polysiloxane backbone and two different mesogenic pendant groups, one involving a vinylacetic acid moiety in the spacer, have been synthesised. Thermal characterisation of these polymeers has allowed comparison of behaviour between a number of different copolymer systems. It was found that increasing amounts of the vinylacetic acid moiety lowered the clearing points (T_i) of the copolymers in an almost linear fashion whilst also inhibiting crystallinity in these polymers.     

INFLUENCE OF THE PULLING OF EMBEDDED NATURAL FIBERS ON THE CRYSTAL STRUCTURE OF POLYPROPYLENE MATRIX

The formation of hexagonal modification (β) of isotactic polypropylene (iPP) matrix, induced by motion of embedded natural fibers (NF) has been investigated by WAXS method. Untreated and chemically modified flax as well as hemp fibers were used as NF. The motion temperature of NF was found to strongly influence the content of hexagonal modification. If the temperature of motion of NF is lower, then the amount of β-iPP significantly increases. The content of β-iPP also depends on the rate of motion of NF; however, the chemical modification of NF surface reduces the content of this form.     

X-ray analysis of α-, β-, and γ-phase Ag–Hg alloy films produced on polymer substrates by casting polyacrylamide–AgNO3 aqueous solution in Hg atmosphere

It is reported that, by dropping Hg metal on the wet α-phase Ag–Hg alloy film formed on the cast polyacrylamide–AgNO₃ aqueous solution, the α phase of fcc structure can be converted into other phases that contain more Hg. The X-ray analysis of these phases reveals that they are the β phase of hexagonal structure and the γ phase of bcc structure. It is also shown that the lattice constant of the α phase can be controlled to some extent by pH of the aqueous solution of PAAm from which the alloy film is formed.     

Hexagonal OsB2 reduction upon heating in H2 containing environment

The stability of hexagonal ReB₂ type OsB₂ powder upon heating under reforming gas was investigated. Pure Os metal particles were detected by powder X-ray diffraction starting at 375°C and complete transformation of OsB₂ to metallic Os was observed at 725°C. The mechanisms of precipitation of metallic Os is proposed and changes in the lattice parameters of OsB₂ upon heating are analysed in terms of the presence of oxygen or water vapour in the heating chamber. Previous studies suggested that Os atoms possess (0) valence, while B atoms possess both (+3) and (?3) valences in the alternating boron/osmium sheet structure of hexagonal (P63/mmc, No. 194) OsB₂; if controllable method for Os removal from the lattice could be found, the opportunity would arise to form two-dimensional (2D) layers consisting of pure B atoms.     

Density and phase equilibrium for ice and structure I hydrates using the Gibbs–Helmholtz constrained equation of state

A new, rigorous framework centered around the multi-scale GHC equation of state is presented for predicting bulk density and phase equilibrium for light gas–water mixtures at conditions where hexagonal ice and structure I hydrate phases can exist. The novel aspects of this new framework include (1) the use of internal energies of departure for ice and empty hydrate respectively to determine densities, (2) contributions to the standard state fugacity of water in ice and empty hydrate from lattice structure, (3) computation of these structural contributions to standard state fugacity from compressibility factors and EOS parameters alone, and (4) the direct calculation of gas occupancy from phase equilibrium. Numerical results for densities and equilibrium for systems involving ice and/or gas hydrates predicted by this GHC-based framework are compared to predictions of other equations of state, density correlations, and experimental data where available. Results show that this new GHC-based EOS framework accurately predicts the densities of hexagonal water ice and structure I gas hydrates as well as phase equilibrium for methane–water and CO₂–water mixtures.     

The effect of anions of transition metal salts on the structure of modified mesostructured silica films and monoliths

The structure of the preformed LC mesophase of water:transition metal salt ([M(H₂O)₆]X₂):acid (HX):oligo(ethylene oxide) (or Pluronics):tetramethylorthosilicate (TMOS) mixture during hydrolysis and partial polymerization of the silica source is maintained upon further polymerization and condensation of the silica species in the solid state. The liquid mixture in early stage of the silica polymerization could be casted or dip coated to a surface of a glass or silicon wafer to produce mesostructured silica monoliths and films, respectively. The silica species and ions (metal ions and anions) influence the structure of the LC mesophases (as a result, the structure of silica) and the hydrophilic and hydrophobic balance in the reaction media. The silica structure can be changed from hexagonal to cubic by increasing, for example, the nitrate salt concentration in the nitrate salt systems. A similar transformation takes place in the presence of very low perchlorate salt concentration. The salt concentration in the mesostructured silica can be increased up to 1.1/1.0 salt/SiO₂ w/w ratio, in mesostructured silica materials by maintaining its lamella structure in P123 and cubic in the C_nEO_m systems. However, the materials obtained from the P123 systems undergo transformation from lamella to 2D hexagonal upon calcinations. The method developed in this work can be used to modify the internal surface of the pores with various transition metal ions and metal oxides that may find application in catalysis.     

Spherulitic crystallization in poly(bis(trifluoroethoxy)phosphazene), PBFP

Spherulite formation in poly(bis(trifluoroethoxy)phosphazene) has been investigated from the melt and from solution over a relatively wide crystallization and annealing range. Three polymorphic forms and one mesoform is found in this polymer. Several of these crystal modifications coexist in amounts which depend upon the crystallization conditions. Negatively birefringent spherulites increase in birefringence slightly upon being heated through the thermotropic T(1) transition. This change involves the formation of a chain extended morphology from a chain folded one. Microbeam X-ray analysis made within the spherulite shows that the unit cell [a] direction is along the spherulite radius while the [c] chain direction lies transverse to the spherulite radius. Moreover, below T(1) it has been established that the X-ray long period is invariant with annealing time and temperature, and above T(1) the periodicity disappears, or cannot be recorded. Whenever heating or cooling occurs through T(1), the spherulite birefringence appears to be invariant after initially heating through T(1). However, a substantial volume change (by dilatomery) of 6% occurs through T(1) and this is consistent with a change in crystal structure from a 3D orthorhombic structure below, to a 2D hexagonal form above T(1). From the molten state the transformation occurs rapidly from isotropic to the 2D form of the mesostate, not far below T_m. The 2D hexagonal form reverts to 3D chain extended orthorhombic on cooling below T(1). This stable chain extended morphology also arises whenever PBFP is melted and then cooled below T(1). All transformations from the isotropic melt or the folded chain conformation must pass through the mesophase. All specimens are friable upon cooling below T(1), whereas the solution case spherulitic polymer film is ductile here.     

Insight into the liquid crystalline behavior of poly-{2,5-bis[(4-butoxyphenyl)oxycarbonyl]styrene}: a typical thermotropic mesogen-jacketed liquid crystalline polymer

Based on the thermodynamic and kinetic analyses, the thermotropic hexagonal columnar liquid crystalline (LC) phase of poly-{2,5-bis[(4-butoxyphenyl)oxycarbonyl]styrene} (PBPCS) at high temperature is self-assembled by driving forces of the conformation entropy and macromolecular interaction, respectively. Because of the strong ??coupling effect?? between flexible backbone and rigid side chain, the molecular structure of PBPCS can be regarded as ??dual chains?? model that a flexible backbone and a rigid side chain are in parallel, the backbone and side chain are corresponded to different molecular thermal motion characteristics. When the orientation requirements of the side mesogenic chain are dominant, LC phase appears; when the random motions of flexible backbone are dominant, LC phase disappears. PBPCS demonstrates various types of metastable phases in the LC phase transition. Above LC phase transition temperature, molecular motion of rigid side chain is dominant; therefore, LC phase is formed. In the temperature range from glass transition to LC phase transition, molecular motion of flexible backbone is dominant; therefore, metastable LC phase may be relaxed partly and even disappear. The stability of LC phase can be determined by the kinetic factors, it is related to the residence time for LC phase formation and the interaction among the aggregated columnar macromolecular chains. Metastable LC phase disappeared in the subsequent cooling procedure, however, the stable LC phase was not.     

Comparative structural studies of poly(heptamethylene p,p′‐bibenzoate) by X‐ray diffraction,positron annihilation and microhardness

The structure of quenched samples of a polybibenzoate with a spacer containing seven methylene units has been studied by wide angle X‐ray scattering (WAXS), microhardness (MH) methods and positron annihilation lifetime spectroscopy (PALS). It was established that the quenched samples of poly(heptamethylene p,p′‐bibenzoate) (P7MB) contain three phases simultaneously: smectic liquid crystalline, amorphous, and a small amount of crystalline one. The d‐spacing of the crystal peaks, together with the crystal and smectic domain dimensions in the direction normal to the mesogen planes and the factor of paracrystallinity, were calculated. The average distance between macromolecules determined from the position of the amorphous halo correlates with the open pore diameter obtained by the PALS analysis. On the basis of MH measurements it was considered that the phases are not uniformly distributed in the depth of the sample, so that the smectic phase prevails in the surface layer while the inner layers are partially crystalline. © 2003 Society of Chemical Industry     

On hexagonal phases of paraffins and polyethylenes

Polyethylene, when irradiated to doses exceeding ca500 Mrad forms a hexagonal structure before melting at atmospheric pressure. The phase diagrams of irradiated polyethylenes have been studied as a function of pressure to 5 kbar, and used as a basis for comparing the radiation-induced hexagonal phase with the hexagonal and pseudo-hexagonal rotator phases of n-paraffins and with the disordered hexagonal (anabaric) structure formed by linear polyethylene at high pressure. At atmospheric pressure, the radiation-induced hexagonal phase is intermediate in character between the other two. It is, nevertheless, a high entropy phase whose temperature interval of existence widens, and whose nature moves towards that of the anabaric phase, with increasing pressure.     

Synthesis of rodlike polysiloxane containing polyol moieties derived from glucose with regularly controlled higher-ordered structure

A rodlike polysiloxane (3) containing polyol moieties derived from the sugar has been synthesized by reaction of an amine-functionalized rodlike polysiloxane (1) with gluconolactone (2) in the presence of triethylamine in DMF. Formation of 3 was estimated by the IR and ¹H NMR measurements. The functionality of 2 to the amino groups in 1 was ca. 75%, based on the ¹H NMR spectrum of the product. The XRD profile of 3 showed three peaks for a typical hexagonal phase, and the d-value of (100) peak of 3 was larger than that of 1, indicating the regularly controlled higher-ordered structure of 3.     

Formation and transformation of hierarchical structure of β-nucleated polypropylene characterized by X-ray diffraction, differential scanning calorimetry and scanning electron microscopy

Commercial grade isotactic polypropylene has been modified with a specific β-nucleant (N,N′-dicyclohexylnaphthalene-2,6-dicarboxamide) in two concentrations (0.03 and 0.10 wt%). Specimens for structural characterization have been prepared by injection moulding, subsequent melting and re-crystallization or solid-state drawing at 100 °C. Individual levels of hierarchical structure, including molecular orientation, have been characterized by a combination of wide angle X-ray scattering (WAXS), differential scanning calorimetry and scanning electron microscopy. Based on the analysis of the azimuthal reflections (110) and (300), the Hermans orientation functions have been calculated separately for the crystalline phases α and β. Besides the longitudinal orientation along the injection-moulding direction, β-crystallites tilted to the injection-moulding direction have been found. Upon thermal treatment the fraction of the crystalline β-phase has decreased and molecular alignment within the crystalline regions has improved. During solid-state drawing the fraction of the crystalline β-phase was markedly decreasing with increasing draw ratio, while the overall crystallinity has not changed but slightly. The experiments have also revealed a disruption of molecular alignment at the beginning of the drawing process and subsequent distinct improvement of molecular orientation along the draw direction in crystallites α and β. The Hermans orientation functions provided by the WAXS analysis have been compared with recently published data obtained with similar specimens by polarized photoacoustic spectroscopy.