Iranian polymer journal
Volume:21 Issue: 11, 2012

An emulsion polymerization of aniline was performed in a solution of dodecylbenzenesulfonic acid emulsifier, benzoyl peroxide oxidant and tartaric acid as dopant. The polyaniline-containing coating was applied over carbon steel panels and the polyaniline content in the coating was 1 %. The influence of reactants concentration on the morphological and anti-corrosive properties of polyaniline was investigated to determine the optimum conditions for the synthesis of polyaniline nanoparticles. The average size of particles determined by X-ray diffraction measurement was 70–104 nm, which is found to be in agreement with the scanning electron microscopy results. Corrosion resistance of coatings was obtained using electrochemical techniques (electrochemical impedance spectroscopy and open circuit potential measurements) in 3.5 % sodium chloride solution. Nyquist diagrams showed two capacitance loops, one at high frequency range followed by a larger one at low frequencies due to coating and charge transfer resistance. The corrosion resistance values were found to decrease due to the corrosion of carbon steel in pinholes of the coating. For longer immersion times, the coating resistance values were found to increase due to the passivation effect of polyaniline. The results showed that epoxy coating with doped polyaniline nanoparticles is able to offer protection in sodium chloride solution.

Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP)-based gel polymer electrolytes (GPEs) with polyvinylpyrrolidone (PVP) and urea as a pore forming agent, respectively, were fabricated by phase inversion method. Physicochemical properties of the as-prepared polymer electrolytes were characterized by SEM, XRD, TG, electrochemical impedance spectroscopy (EIS) and linear sweep voltammetry (LSV). The results showed that the GPE membranes using urea as pore forming agent present a uniform surface with abundant interconnected micro-pores and possess upto 330 °C decomposition temperature; the XRD patterns indicate that adding urea into the polymer matrix can attain more amorphous areas than adding PVP; the reciprocal temperature dependence of ionic conductivity of as-prepared GPEs follows Vogel-Tamman-Fulcher relation and the ionic conductivity at room temperature is 2.212 mS cm−1 for PVP pore forming GPEs and 2.823 mS cm−1 for urea pore forming GPEs, respectively; the interfacial resistance of the Li/GPEs/Li cell using urea as pore forming agent can achieve a quick steady value of about 660 Ω cm−1 lower than that of PVP of about 760 Ω cm−1 during the same storage conditions; the electrochemical stability window of the GPEs with urea can be stable upto 5.0 V (vs. Li+/Li) at room temperature. The battery performance of the assembled Li/GPEs/LiCoO2 coin cell also showed that the cell using urea as pore forming agent in GPEs demonstrated excellent first charge/discharge rate and cycle performances. These excellent physicochemical and battery properties indicated that urea can be used as a kind of excellent pore forming agent for polymer electrolytes in the lithium-ion polymer battery.

In recent years, with growing contradiction between energy supply and demand, the more and more high demand of the environmental protection is needed. The work represented an environment friendly method for recycling of waste rubber and pulp sediment that a new composite material was prepared using pulp sediment as the matrix, used rubber powder as the toughening agent, and sawdust as the reinforcement. The effects of used rubber powder content on the mechanical properties of the pulp sediment and sawdust/pulp sediment were studied by measuring Shore A hardness, tensile stress, and elongation-at-break. The morphology of used rubber powder/pulp sediment composites was analyzed by scanning electronic microscopy and transmission electron microscopy. The curing conditions were also discussed. The results showed when the used rubber powder/pulp sediment mass ratio was 8/100, the used rubber powder/pulp sediment sample showed smooth surface, high hardness, compact structure, uniform arrangement, and good compatibility. When the pulp sediment used as the matrix, sawdust as the reinforcement, and used rubber powder as the toughening agent, the proper recipe of the composites was 100 phr pulp sediment, 30 phr sawdust, and 10 phr used rubber powder. The mechanical properties of the used rubber powder/pulp sediment were greater than those of pure pulp sediment and used rubber powder/sawdust/pulp sediment. The best curing conditions for the used rubber powder/pulp sediment composites were at 150 °C under 5 MPa for 15 min. The study on used rubber powder modified pulp sediment, exploits a new way to recycle used rubber powder and pulp sediment, not only benefit environment purification, but also reduce cost of sheet materials, and develops a new way for the economy and environment protection.

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.

A novel water-soluble block polypseudorotaxane (4) was synthesized in water from cucurbit[n]uril (n = 6), designated as CB[6], and a block copolymer of methoxy poly(ethylene glycol)-b-poly-[N 1-(4-vinylbenzyl)-pentane-1,5-diamine dihydrochloride]-b-methoxy poly(ethylene glycol) (P3). Driven by the hydrophobic/hydrophobic interaction and the association between the diamine and glycoluril units, CB[6] beads are localized on the pentamethylene units in the side chains of P3 as found by NMR studies. The degree of threading, i.e., the average number of CB[6] beads per repeat recognition unit of P3, can be controlled from 0.25 to 1.0 by varying the amount of CB[6] added. This molecular feature leads to interesting aggregation behavior of the polypseudorotaxanes in aqueous solutions, as revealed by dynamic light scattering measurements, transmission electron microscopy observations, ultraviolet/visible spectroscopy (UV–vis) and fluorescence spectrometry. The average hydrodynamic radius (R h), the intensity of UV–vis absorption band and the fluorescence intensity (I f) of the block polypseudorotaxanes in solution increase with the increasing of threaded CB[6]. With the solution temperature increasing, the size of the aggregates in water increased and the fluorescence intensity (I f) of the solution decreased, which shows the polypseudorotaxanes can sensitively respond to temperature changes. This opens the door for the application of the block polypseudorotaxanes in various fields such as drug delivery and controlled release.

A series of Na-montmorillonite (Na+-MMT) modified acrylic impact modifiers (mAIM) were prepared by seeded emulsion polymerization. These mAIM modifiers were characterized by XRD. A 0.24 nm of increased interlayer distance of Na+-MMT was an indication of polymer chains intercalation within interlayer spacing. The notched Izod impact tests proved that the impact strength of the PVC/AIM composites prepared by melt blending was 43 J/m, markedly higher than the impact strength of pure PVC. Furthermore, with increasing content of AIM, the composites exhibited changes from brittle fracture to ductile fracture, with the impact strength increasing from 200 to about 1,000 J/m. The impact strength of PVC/mAIM also showed the same trend, although there were drops in some values. The impact strength of PVC/mAIM composites decreased with the increases in Na+-MMT content, but the yield strength and modulus of the composites increased with higher Na+-MMT content. The result also showed that the tensile strength of mAIM with 2 wt % Na+-MMT is lower than that of mAIM with 0.8 and 1 wt % contents, but still sufficiently large in comparison to the tensile strength of mAIM with 0 wt % Na+-MMT. The dynamic mechanical analysis (DMA) result showed that the glass transition temperature (T g) of mAIM did not show obvious changes and the elasticity of mAIM was reduced with the additional Na+-MMT content.

Schottky-barrier diode devices were fabricated in a sandwich configuration with poly(pyrrole-co-indole) copolymer semiconducting films prepared by electropolymerization. Effect of different dopants of ClO4 −, BF4 −, C7H7SO3 − and [Fe(CN)6]3− on the electronic properties of the fabricated devices was followed using Ag, In, Al and Cu metal junctions. Current–voltage and capacitance–voltage characteristics were recorded for making a comparative evaluation of the electronic and junction properties of the devices. The electrical characteristics of the junctions were analyzed based on the standard thermionic emission theory. Polymer doped by ClO4 − showed lower reverse saturation currents and ideality factor but higher potential barriers and rectification ratios. Effect of dopant ions and copolymerization on the optical band gaps (E g) of the films were investigated and the optical transmissions of the doped copolymer films were measured in the wavelength range of 250–900 nm. It was shown that the energy gap of copolymers laid between those of corresponding homopolymers and polyindole (PIN) doped by [Fe(CN6)]−3 had E g less than that of polymer doped by other anions whereas E g of polypyrrole was independent of dopant ions. Also, the morphology of the polymeric films revealed the surface of the PIN doped with ClO4 − was very smooth which created a good contact with indium metal.

This study deals with the preparation of carboxylated styrene butadiene rubber (XSBR)/multiwall carbon nanotubes (MWCNTs) nanocomposites prepared in the latex form by means of a ball mill. Two types of CNTs, i.e., non-functionalized and OH-functionalized (CNT–OH) were used. The rheological properties, FTIR spectrums, SEM micrographs and stress relaxation experiments were exploited to evaluate the resulting nanocomposites. For a given frequency, both the viscosity and storage modulus increased as the concentration of CNT was augmented with the greatest value for the nanocomposites loaded with CNT–OH. The viscosity of nanocomposites exhibited a shear thinning behavior throughout applied frequency and indicated a power law index of about n = 0.22. Nanocomposite ATR analyses revealed the presence of physical interaction of H-bonding type between hydroxyl group of CNT–OH and carboxyl group of XSBR for XSBR–CNTOH nanocomposites. A mechanism based on the chemistry of medium was proposed to explain the development of H-bonding. SEM micrographs confirmed the uniformity of carbon nanotubes dispersion in the resulting microstructure. A two-step innovative stress relaxation experiment was performed on the prepared nanocomposites through which the resulting microstructure of nanocomposites was further explored. The relaxation behavior of nanocomposites (both in first and second steps) were modeled and well predicted using Prony series and the parameters of generalized Maxwell equation for stress relaxation, τi and gi were computed, as well.