Shear induced molecular alignments of a side-chain liquid crystalline polyacetylene containing biphenyl mesogens

Mesomorphic properties of a side chain liquid crystalline polyacetylene, poly(11-{[(4'-heptyloxy-4-biphenylyl)carbonyl]oxy}-1-undecyne) (PA9EO7), are investigated using polarized optical microscope, X-ray diffraction, and transmission electron microscope. Polymer PA9EO7 forms enantiotropic smectic A and smectic B phases. It also exhibits an additional high order smectic phase, a sandwich structure consisting of different molecular packing of biphenyl mesogenic moieties from that of alkyl spacers and terminals, when it is prepared from its toluene solution. Shearing the polymer film at its smectic A phase generates banded texture with the alignment of the backbones parallel to the direction of shear force. While at its high order smectic phase, the mesogen pendants of the polymer are arranged parallel to the direction of shear. The different mesomorphic behaviors arise from different molecular alignments influenced by the fluidity.

High order liquid crystalline structure of poly(11-{[(4 '-heptyloxy-4-biphenylyl)carbonyl]oxy}-1-undecyne)

Liquid crystalline properties of a mesomorphic polyacetylene {-[HC=C(CH2 )(9)OOC-Biph-OC7H15](n)- (PA9EO7), Biph=4-4'-biphenylyl} are investigated by X-ray diffraction, polarizing optical microscope, and transmission electron microscope. Polyacetylene PA9EO7 from solution adopts a sandwich structure, which is a high order smectic phase. The biphenylyl pendants pack in a hexagonal fashion and the distance between two appendages is 4.51 Angstrom. The heptyloxy tails on one polymer backbone overlap with those on the neighboring chain. The nonyl spacer and the heptyloxy tail exhibit a hexagonal packing arrangement with intermolecular distance of 3.24 Angstrom.

Crystal structure of 11-{[(4 '-heptoxy-4-biphenylyl) carbonyl]oxy}-1-undecyne

The crystal structure of 11-{[(4'-heptoxy-4-biphenylyl) carbonyl] oxy}-1-undecyne (A9EO7), an acetylene with a biphenyl mesogenic moiety, was studied by combination of electron diffraction (ED), wide-angle X-ray diffraction (WAXD), and molecular simulation of ED pattern and molecular packing. A9EO7 was found to adopt an orthorhombic P2(1)2(1)2 space group with cell parameters of a = 5.78 Angstrom, b = 7.46 Angstrom, and c = 63.26 Angstrom, for which molecular packing calculations were conducted to elucidate the molecular conformation. Its crystal morphology was observed using a transmission electron microscope (TEM) and an atom force microscope (AFM). A9EO7 crystal grew to form step like morphology. Crystallization behavior of A9EO7 in magnetic field was examined. Induced by magnetic field A9EO7 could crystallize in such a way that its molecular long axis was parallel to the substrate.

Silicon dioxide coating of CeO2 nanoparticles by solid state reaction at room temperature

The synthesis Of SiO2 coated CeO2 nanoparticles by humid solid state reaction at room. temperature is described. Transmission electron microscope results show that CeO2 Particles were coated with a layer Of SiO2. Binding energy of Ce 3d(5/2) was shifted from 883.8 to 882.8 eV after coating in the XPS Ce 3d spectra. This confirms the chemical bond formation between SiO32- and Ce4+. Because the surface photovoltage property of CeO2 nanoparticles that were used as core materials in the experiment approaches to that of CeO2 macroparticles, peak P2 (electron transition from 0 2p on surface to Ce 4f) disappeared in the surface photovoltage spectrum of CeO2 nanoparticles. Also, the effect Of SiO2 on the electron transition from 0 2p to Ce 4f results in the lowering of surface photovoltage response intensity of P1 peak (electron transition from 0 2p in bulk to Ce 4f).

The preparation of phenolic resin/montmorillonite nanocomposites by suspension condensation polymerization and their morphology

Phenolic resin/clay nanocomposites were prepared using a suspension condensation polymerization method that was suitable to both novolac and resole. Natural montmorillonite and two kinds of organic modified montmorillonite were adopted to investigate the effect of modification on the final morphology of the nanocomposites. X-ray diffraction (XRD) measurements and Transmission Electron Microscope (TEM) observations showed that clay platelets were easier to be exfoliated or intercalated in novolac than in resole because novolac usually has a linear structure. The modifier with a phenyl ring was more compatible with novolac (or resole) than the aliphatic type modifier. The influence of curing on the morphology was studied as well. An exfoliation-adsorption and in situ condensation mechanism was proposed on the formation of the nanocomposites.

Coating of Y2O3 : Eu3+ particles with alumina by a humid solid state reaction at room temperature

Humid solid state reaction at room temperature was utilized for the first time to coat Y2O3 : Eu3+ particles with alumina. The particles were studied with an X-ray photoelectron spectrometer (XPS), a scanning electron microscope (SEM), and an energy dispersive spectrometer (EDS). XPS results show that the yttrium and europium contents are decreased and that the aluminum content is the highest except for that of oxygen after coating. SEM and EDS results show that particles are coated with a thin shell of alumina.

Preparation and properties of conductive polyaniline/poly-omega-aminoundecanoyle fibers

Historically, polyaniline (PANI) had been considered an intractable material, but it can be dissolved in some solvents. Therefore, it could be processed into films or fibers. A process of preparing a blend of conductive fibers of PANI/poly-omega-aminoun-decanoyle (PA11) is described in this paper. PANI in the emeraldine base was blended with PA11 in concentrated sulfuric acid (c-H,SO,) to form a spinning dope solution. This solution was used to spin conductive PANI/PA11 fibers by wet-spinning technology. As-spun fibers were obtained by spinning the dopes into coagulation bath water or diluted acid and drawn fibers were obtained by drawing the as-spun fibers in warm drawing bath water. A scanning electron microscope was employed to study the effect of the acid concentration in the coagulation bath on the microstructure of as-spun fibers. The results showed that the coagulating rate of as-spun fibers was reduced and the size of pore shrank with an increase in the acid concentration in the coagulation bath. The weight fraction of PANI in the dope solution also had an influence on the microstructure of as-spun fibers. The microstructure of as-spun fibers had an influence on the drawing process and on the mechanical properties of the drawn fibers. Meanwhile, the electrically conductive property of the drawn fibers with different percentage of PANI was measured.

Reactive reinforcement of the interface of poly(ether sulfone)/poly(phenylene sulfide) polymer blend by PMR-POI

The effect of polymerization of monomer reactant-polyimide (POI) as the interfacial agent on the interface characteristics, morphology features, and crystallization of poly(ether sulfone)/poly(phenylene sulfide) (PES/PPS) blends were investigated using a scanning electron microscope, FTIR, WAXD, and XPS surface analysis. It was found that the interfacial adhesion was enhanced, the particle size of the dispersed phase was reduced, and the miscibility between PES and PPS was improved by the addition of POI. It was also found that POI was an effective nucleation agent of the crystallization for PPS.

Preparation of the HIPS/MA graft copolymer and its compatibilization in PA6/HIPS blends

The graft copolymer of high impact polystyrene (HIPS) grafted with malice anhydride (MA) (HIPS-g-MA) was prepared with melt mixing in the presence of a free-radical initiator. The grafting reaction was confirmed by IR analyses and the amount of MA grafted on HIPS was evaluated by a titration method. 1-5 wt% of MA can be grafted on HIPS. HIPS-g-MA is miscible with HIPS. Its anhydride group can react with the PA6 during melt mixing the two components. The compatibility of HIPS-g-MA in the HIPS/PA6 blends was evident. Evidence of reactions in the blends was confirmed in the morphology and mechanical properties of the blends. A significant reduction in domain size was observed because of the compatibilization of HIPS-g-MA in the blends of HIPS and PA6. The tensile mechanical properties of the prepared blends were investigated and the fracture surfaces of the blends were examined by means of the scanning electron microscope (SEM). The improved adhesion in a 16%HIPS/75%PA6 blend with 9%HIPS-g-MA copolymer was detected. The morphology of fibrillar ligaments formed by PA6 connecting HIPS particles was observed.

Initiation and termination of crazes in high impact polystyrene

Initiation and termination of crazes in high impact polystyrene (HIPS) were studied by transmission electron microscope. Instead of the first initiation of crazes in the vicinity of the equator or rubber particles, ribbon-shaped crazes beyond the region were observed on the TEM photos. The starting point and the end point of each ribbon were noticed not to be randomly located on the surface of the cellar particles in HIPS. The spots connecting to the ligaments between the PS rigid inclusions in the cellar particle are found to be the locations where crazes were initiated and terminated preferentially. In addition, the crazes generated at those spots were much thicker and longer. The thoughness of high impact polystyrene was enhanced by the multiple crazes formed in the matrices, through the reduction of the craze stress at room temperature with increasing the volume fraction of polybutadiene at these spots in the dispersed phase. These results conducted that not only the cell structure of the domains in HIPS was not homogeneous but also the polybutadiene ligaments between PS rigid inclusions in the domains were inhomogeneous. Therefore, the responsibility of those polybutadiene ligaments with different thickness to the stresses was different and it forced the crazing initiation and growing preferentially. The crazes were created in some regions in the matrices; On the contrary, rare crazes were formed in the other regions in spite of these regions surrounded around the same dispersed particles. The relation between the spots on the surface and the inner structure of the cellar particle was discussed in this paper.

Morphology, thermal behavior, and mechanical properties of PA6/UHMWPE blends with HDPE-g-MAH as a compatibilizing agent

A functionalized high-density polyethylene (HDPE) with maleic anhydride (MAH) was prepared using a reactive extruding method. This copolymer was used as a compatibilizer of blends of polyamide 6 (PA6) and ultrahigh molecular weight polyethylene (UHMWPE). Morphologies were examined by a scanning electron microscope. It was found that the dimension of UHMWPE and HDPE domains in the PA6 matrix decreased dramatically, compared with that of the uncompatibilized blending system. The size of the UHMWPE domains was reduced from 35 mu m (PA6/UHMWPE, 80/20) to less than 4 mu m (PA6/UHMWPE/HDPE-g-MAH, 80/20/20). The tensile strength and Izod impact strength of PA6/UHMWPE/HDPE-g-MAH (80/20/20) were 1.5 and 1.6 times as high as those of PA6/UHMWPE: (80/20), respectively. This behavior could be attributed to chemical reactions between the anhydride groups of HDPE-g-MAH and the terminal amino groups of PA6 in PA6/UHMWPE/HDPE-g-MAH blends. Thermal analysis was performed to confirm that the above chemical reactions took place during the blending process. (C) 2000 John Wiley & Sons, Inc.

Morphology of conductive blend fibers of polyaniline and polyamide-11

Polyaniline (PANI), a member of the intrinsically conducting polymer (ICPs) family, was blended with polyamide-11 (polyco-aminoundecanoyle) in concentrated sulfuric acid. The above solution was used to spin conductive PANI/polyamide-11 fibers by wet-spinning technology. Scanning electron microscope (SEM) and transmission electron microscope (TEM) were employed to study the two-phase morphology of the conductive PANI/polyamide-11 fibers. The micrographs of the cross-section, the axial section and the surface of the monofilament demonstrated that the two blend components were incompatible. The morphology of PANI in the fibers was of fibrillar form, which was valuable for producing conducting channels. The electrical conductivity of the fibers was from 10(-6) to 10(-1) S/cm with the different PANI fraction and the percolation threshold was about 5 wt.%. By comparing the two blend systems of PANI/Polyamide-11 fibers and carbon black filled poly(ethylene terephthalate) (PET) fibers, it was shown that the morphology of the conductive component had an influence on electrical conductivity, The former had higher conductivity and lower percolation threshold than the latter. (C) 2001 Elsevier Science B.V. All rights reserved.

Studies on the morphology transition of micro-crystal growth in polymer films in high vacuum and strong electrostatic field

The morphology of films of isotactic polypropylene poly (3-dodecylthiophene) and iPP/P3DDT blend formed in electrostatic fields has been investigated by using scanning electron microscope. The experiment results show that the micro-crystal morphology of polymer films was strongly dependent on electrostatic fields. It was found that the effect of the electrostatic field led to the formation of dendrite crystals aligned in the field direction, and some branches of P3DDT ruptured. However, the micro-crystals in these films grew into spherulites without electrostatic field,and have no crystal orientation.

The effect of electrostatic field on the micro-crystal morphology of polymer films

The micro-crystal morphology of the films of isotactic polypropylene (iPP), poly(3-dodecylthiophene) (P3DDT) and iPP/P3DDT blend grown in different electrostatic environments has been investigated by using scanning electron microscope. The experimental results show that the micro-crystal morphology of polymer films was strongly dependent on electrostatic field. It was found that the micro-crystal morphology of the films of iPP, P3DDT and iPP/P3DDT blend grown in the electrostatic field was in the form of dendrite crystals, in which main stems were aligned in the field direction, and some branches of P3DDT were ruptured. However, the micro-crystals of the films of iPP, P3DDT and iPP/P3DDT blend have no crystal orientation in the absence of electrostatic field. (C) 2001 Elsevier Science Ltd. All rights reserved.

Study of the mechanism for controlled crystallization of BaF2 under two kinds of monolayers

Controlled crystallization of BaF2 under two different kinds of monolayers, octadecylamine [CH3(CH2)(17)NH2] and hexadecanol [CH3(CH2)(14)CH2OH], has been studied by using x-ray diffraction (XRD) and scanning electron microscope. It was found that the monolayer headgroup, the degree of ionization of the headgroup, etc., had a complicated effect on the selectivity of monolayers for crystal and on the morphology and orientation of crystals grown under the compressed monolayers. At pH = 7.0, XRD analysis showed that (100)-oriented BaF2 crystals were formed under the octadecylamine monolayer, while several kinds of crystals were found under the hexadecanol monolayer. In comparison, at pH = 8.5, both (100)-oriented BaF2 and (111)-oriented Ba(NO3)(2) crystals were obtained under the monolayer of octadecylamine. However, crystals formed under hexadecanol monolayer consist of BaF2, Ba(NO3)(2), etc. The detailed mechanism for crystallization was discussed in terms of the specific interaction and lattice matching between the monolayer headgroup and the nucleating species.