Morphological study on water-borne conducting polyaniline-poly(ethylene oxide) blends

Conducting polyaniline-poly(ethylene oxide) blends were prepared from their aqueous solutions. The blends displayed an electrical conductivity percolation threshold as low as 1.83 wt % of polyaniline loading. As demonstrated by scanning electron microscopy, polarized optical microscopy, and wide-angle X-ray diffraction studies, the conducting polyaniline took a fibrillar morphology in the blend, and it existed only in the amorphous phase of poly(ethylene oxide). A three-phase model combining morphological factors instead of a two-phase model was proposed to explain the low-conductivity percolation threshold.

Characterization and properties of the neutral and doped blends of poly(3-dodecylthiophene) with low-density polyethylene

In this paper, the structures and properties of the neutral and doped blends of poly(3-dodecylthiophene) (P3DDT) with low-density polyethylene (LDPE) were investigated. Wide-angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), Fourier transform infrared spectra (FTIR), and scanning electron microscopy (SEM) were used to characterize the structures and morphologies of the blends, and conductivity was also measured. It was found that separate crystallizations occur between P3DDT and LDPE. When the amount of P3DDT is small in the blend, it has the effect of a nucleation reagent and has some influence on the crystal structure. After doping, the interaction force between the molecular chains increases, and leads to a more compact packing and a more uniform dispersion in morphology. Through blending, the thermal stability of pure component could be greatly improved, especially when the P3DDT content is 5 wt %. The conductivity measurements indicate that the conductivity increases with the increase of the P3DDT composition and doping time.

Crystallization and Crosslinking of polyamide-1010 under elevated pressure

The structure and thermal properties of polyamide-1010 (PA1010), treated at 250degreesC for 30 min under pressures of 0.7-2.5 GPa, were studied with wide-angle X-ray diffraction (WAXD), infrared (IR), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). Crystals were formed when the pressures were less than 1.0 GPa or greater than 1.2 GPa. With increasing pressure, the intensity of the diffraction peak at approximately 24degrees was enhanced, whereas the peak at approximately 20degrees was depressed. The triclinic crystal structure of PA1010 was preserved. The highest melting temperature of the crystals obtained in this work was 208degreesC for PA1010 treated at 1.5 GPa. Crosslinking occurred under pressures of 1.0-1.2 GPa. Only a broad diffraction peak centered at approximately 20degrees was observed on WAXD patterns, and no melting and crystallization peaks were found on DSC curves. IR spectra of crosslinked PA1010 showed a remarkable absorption band at 1370 cm(-1). The N-H stretching vibration band at 3305 cm(-1) was weakened. Crystallized PA1010 had a higher thermal stability than crosslinked PA1010, as indicated on TGA curves by a higher onset temperature of decomposition.

Preparation, characterization, and crystallization of naphthalene-labeled polypropylene

Naphthalene-labeled polypropylene (PP) was prepared by melt reaction of maleic anhydride-grafted-polypropylene (PP-g-MA) with 1-aminonaphthalene in a Barabender mixer chamber. The structure of the product was analyzed with fourier transform infrared (FT-IR), ultraviolet (UV) and fluorescence. The results showed that naphthyl groups grafted onto the PP molecular chains through the imide bonds formed between MA and 1-aminonaphthalene. The content of the chromophores was 1.8 X 10(-4) mol g(-1) measured by elemental analysis. Isothermal crystallization behavior was studied by differential scanning calorimeter (DSC). Labeled PP had a higher crystallization rate than PP-g-MA. Wide-angle X-Ray diffraction (WAXD) analysis revealed that labeled PP had higher crystallinity than PP-g-MA.

Formation of a metastable phase induced by a liquid crystalline phase in a novel chloropoly(aryl ether ketone)

The phase transition behavior of a thermotropic liquid crystalline poly(aryl ether ketone) synthesized by nucleophilic substitution reactions of 4,4'-biphenol (BP), and chlorohydroquinone (CH) with 1,4-bis(4-fluorobenzoyl)benzene (BF) has been investigated by differential scanning calorimetry (DSC) and wide angle X-ray diffraction (WAXD). The copolymer exhibits multiple first order phase transitions, which are associated with crystal-to-smectic liquid crystal transition and smectic liquid crystal-to-isotropic transition. When the cooling rate is low (<10C/min), only stable crystal from I is formed. With the cooling rate being high (>20 degreesC/min), the metastable crystal form II is formed, which always coexists with form I. The liquid crystalline phase plays an important role in the formation of metastable phase form II.

Nanostructure and mechanical measurement of highly oriented lamellae of melt-drawn HDPE by scanning probe microscopy

Scanning probe microscopy was used to simultaneously determine the molecular chain structure and intrinsic mechanical properties, including anisotropic elastic modulus and friction, for lamellae of highly oriented high-density polyethylene (HDPE) obtained by the melt-drawn method. The molecular-scale image of the highly oriented lamellae by friction force microscopy (FFM) clearly shows that the molecular chains are aligned parallel to the drawing direction, and the periodicities along and perpendicular to the drawing direction are 0.26 and 0.50 nm, respectively. The results indicate that the exposed planes of the lamellae resulting from the melt-drawn method are (200), which is consistent with results of transmission electron microscopy and electron diffraction. Because of the high degree of anisotropy in the sample, coming from alignment of the molecular chains along the drawing direction, the measured friction force, F, determined by FFM is strongly dependent on the angle, theta, between the scanning direction and the chain axis. The force increases as theta is increased from 0 degrees (i.e., parallel to the chain axis) to 90 degrees (i.e., perpendicular to the chain axis). The structural anisotropy was also found to strongly influence the measurements of the transverse chain modulus of the polymer by the nanoindentation technique. The measured value of 13.8 GPa with transverse modulus was larger than the value 4.3 GPa determined by wide-angle X-ray diffraction, which we attributed to anisotropic deformation of the lamellae during nanoindentation measurements that was not accounted for by the elastic treatment we adopted from Oliver and Pharr. The present approach using scanning probe microscopy has the advantage that direct correlations between the nanostructure, nanotribology, and nanomechanical properties of oriented samples can be determined simultaneously and simply.

Confined crystallization behavior of PCL in organic-inorganic hybrid system

poly(epsilon-caprolactone) (PCL) and silica (SiO2) organic-inorganic hybrid materials have been synthesized by sol-gel approach and the crystalline behavior of PCL in the silica networks has been investigated by differential scanning calorimetry (DSC) and wide angle X-ray diffraction (WAXD). The degree of PCL crystallinity in the PCL/SiO2 hybrid networks reduces with the increase of SiO2 content. PCL is in an amorphous state when the concentration of PCL is lower than 40wt% in the hybrid materials. The melting points of PCL in the networks are lower than that of pure PCL,but they almost have a same value. WAXD results show that when the PCL weight percentage is higher than 40wt% in the hybrid samples,part of PCL can crysatllize and the PCL crystallites are almost in a same size. That means the crystalline movement of PCL molecular chains is strictly confined by the porous gel. The crystalline PCL in the hybrid samples is relatively free from the composition of the materials, because the crystallization temperature and melting point of PCL of the samples are almost equal,and the crystalline PCL of different samples has the same crystalline structure and the same crystallite sizes L-110 and L-200, that means the crystalline part of PCL in the hybrid samples is unperturbed and the porous silica gel gives enough space for PCL to crystallize into the same crystalline structure and the same size crystallites.

Influence of annealing on structure of Nylon 11

Differential scanning calorimeter (DSC), wide-angle X-ray diffraction (WAXD), small-angle X-ray scattering (SAXS), and density techniques have been used to investigate the structural parameters of the solid state of Nylon 11 annealed at different temperatures. The equilibrium heat of fusion Delta H-m(0) and equilibrium melting temperature T-m(0) were estimated to be 189.05 J g(-1) and 202.85 degrees C respectively by using the Hoffman-Weeks approach. The degree of crystallinity (W-c,W-x) ranged approximately 24-42% was calculated by WAXD and compared with those by calorimetry (W-c,W-h) and density (W-c,W-d) measurements. The radius of gyration R-g, crystalline thickness L-c, noncrystalline thickness L-a, long period L, semiaxes of the particles (a, b), electron-density difference between the crystalline and noncrystalline regions eta(c) - eta(a), and the invariant Q increased with increasing annealing temperature. The analysis of the SAXS data was based upon the particle characteristic function and the one-dimensional electron-density correlation function. An interphase region existed between the crystalline and noncrystalline region with a clear dimension of about 2 nm for semicrystalline Nylon 11. Instead of the traditional two-phase model, a three-phase model has been proposed to explain these results by means of SAXS.

Crystallization and melting behavior of amorphous poly(iminosebacoyl iminodecamethylene)

Multiple melting behavior was observed in the differential scanning calorimetry (DSC) scans for the isothermally crystallized poly(iminosebacoyl iminodecamethylene) (PA1010) samples. Coexistence of crystal populations with different lamellar thickness in PA1010 was discussed by means of DSC, wide-angle X-ray diffraction (WAXD), and small-angle X-ray scattering techniques. During crystallization of the polymer, a major lamellar crystal population developed first, which possessed a higher melting temperature. However, a small fraction of the polymer formed minor crystal population with thinner lamellae, which was metastable and, upon post-annealing, could grow into more stable and thicker lamellae through melting and recrystallization process. Lamellae insertion or stacks would develop during the post-annealing at a lower temperature for the isothermally crystallized samples; thus, multiple crystal populations with different thickness could be produced. It is the multiple distribution of lamella thickness that gives rise to multiple melting behavior of crystalline polymers. (C) 2000 John Wiley & Sons, Inc.

Morphology, crystallization behaviors, and mechanical properties of PA1010/HIPS and PA1010/HIPS-g-MA blends

The binary blends of polyamide 1010 (PA1010) with the high-impact polystyrene (HIPS)/maleic anhydride (MA) graft copolymer (HIPS-g-MA) and with HIPS were prepared using a wide composition range. Different blend morphologies were observed by scanning electron microscopy according to the nature and content of PA1010 used. Compared with the PA1010/HIPS binary blends, the domain sizes of dispersed-phase particles in PA1010/HIPS-g-MA blends were much smaller than that in PA1010/HIPS blends at the same compositions. It was found that the tensile properties of PA1010/HIPS-g-MA blends were obviously better than that of PA 1010/HIPS blends. Wide-angle xray diffraction analyses were performed to confirm that the number of hydrogen bonds in the PA1010 phase decreased in the blends of PA1010/HIPS-g-MA. These behaviors could be attributed to the chemical interactions between the two components and good dispersion in PA1010/HIPS-g-MA blends.

Further study on double-melting endotherms of isotactic polypropylene

The origins of the single- and double-melting endotherms of isotactic polypropylene crystallized at different temperatures were studied carefully by differential scanning calorimetry, wide-angle X-ray diffraction, and small-angle X-ray scattering. The experimental data show that spontaneous crystallization occurs when the crystallization temperature is lower than 117 degrees C; thus the lamellae formed are imperfect. At a lower heating rate, the recrystallization or reorganization of these imperfect lamellae leads to double endotherms. On the other hand, when the crystallization temperature is higher than 136 degrees C, two major kinds of lamellae with different thickness are developed during the isothermal process, which also results in the double-melting endotherms. In the intermediate temperature range the lamellae formed are perfect, and there is only a single peak in the distribution of lamellar thickness. This explains the origin of the single-melting endotherm. (C) 2000 John Wiley & Sons, Inc.

Chlorohydrin water swellable rubber compatibilized by an amphiphilic craft copolymer. I. Synthesis and characterization of compatibilizer PVA-g-PBA

The graft copolymerization of butyl acrylate onto poly(vinyl alcohol) with eerie ammonium nitrate as redox initiator in a aqueous medium has been investigated. The formation of graft copolymer was confirmed by means of IR, scanning electron microscopy (SEM), and wide-angle X-ray diffraction (WAXD). The percentage of mononer conversion and percentage of grafting varied with concentrations of initiator, nitric acid, monomer, macromolecular backbone (X-n = 1750, M = 80 000), reaction temperature and reaction time. Some inorganic salts and organic solvents have a great influence upon grafting. The reaction mechanism has been explored, and rate equations for the reaction are established. (C) 2000 John Wiley & Sons, Inc.

Dependence of the Brill transition on the crystal size of nylon 10 10

Nylon 10 10 crystals, which isothermally crystallized from the molten state and cold crystallized from melt-quenched samples at various temperatures, were investigated by using temperature-variable wide angle X-ray diffraction (WAXD) and small angle X-ray scattering (SAXS). No Brill transition occurred for the melt-crystallized crystals. However, this transition was easily observed for the cold-crystallized nylon 10 10, and the transition temperature is pertinent to the crystallization temperature. The sizes of these crystals was determined by SAYS and correlated with the Brill transition temperatures (T-B). It was found that the T-B had a linear relationship with the size of crystals, which was used to predict the T-B for those crystals with thick lamella and to calculate the crystal size showing T-B below room temperature. Nylon 10 10 crystal will possess the gamma form (pseudohexagonal form) rather than the a phase at room temperature if its size becomes small enough.

Influence of temperature on lattice spacings of melt-crystallized poly(iminosebacoyl iminodecamethylene)

The variation of lattice spacings of poly(iminosebacoyl iminodecamethylene) (nylon-10,10) with temperature was studied by wide-angle X-ray diffraction (WAXD) during both heating and cooling processes, which demonstrates a gradual and continuous transition with temperature. However, the crystal melts before the two peaks merge completely. Both WAXD and differential scanning calorimetry show that crystallization from molten sample results directly in the triclinic form. Additionally, this transition is thermodynamically reversible. Comparison of this transition with that of nylon-6,6, suggests that no hydrogen-bonded network is formed during or after the transition. We prefer to attribute this transition to asymmetrical thermal expansion in the nylon-10,10 crystals rather than to a true first-order phase transition. (C) 2001 Society of Chemical Industry.

Study on a series of main-chain liquid-crystalline ionomers containing sulfonate groups

A series of main-chain Liquid-crystalline ionomers containing sulfonate groups pendant on the polymer backbone were synthesized by an interfacial condensation reaction of 4,4'-dihydroxy-alpha,alpha'-dimethyl benzalazine, a mesogenic monomer, with brilliant yellow (BY), a sulfonate-containing monomer, and a 1/9 mixture of terephthaloyl and sebacoyl dichloride. The structures of the polymers were characterized by LR and UV spectroscopies. DSC and thermogravimetric analysis were used to measure the thermal properties of those polymers, and the mesogenic properties were characterized by a polarized optical microscope, DSC, and wide-angle X-ray diffraction. The ionomers were thermally stable to about 310 degreesC. They were thermotropic liquid-crystalline polymers (LCPs) with high mesomorphic-phase transition temperatures and exhibited broad nematic mesogenic regions of 160-170 degreesC, and they were lyotropic LCPs with willowy leaf-shaped textures in sulfuric acid. However, the thermotropic liquid-crystalline properties were somewhat weakened because the concentration of BY was more than 8%. The inherent viscosity in N-methyl-2-pyrrolidone suggested that intramolecular associations of sulfonate groups occurred at low concentration, and intermolecular associations predominated at higher concentration. (C) 2001 John Wiley & Sons, Inc.