Iranian polymer journal
Volume:20 Issue: 10, 2011

N-Substituted polyaniline (poly(N-octadecylaniline)) was prepared throughN-alkylation reaction, by introducing octadecyl chains into a highly stable"leucoemeraldine base" (LEB) form of polyaniline nanostructure synthesized viaa new chemical polymerization method. The polymer was characterized by FTIR,1H NMR and UV-Vis spectroscopy techniques. Thermogravimetry (TG), derivativethermogravimetry (DTG) and differential scanning calorimetry (DSC) methods werecarried out to investigate thermal behaviour of the obtained poly (N-octadecylaniline).Thermal analysis showed two endothermic transitions at 41°C and 60°C during theheating and two exothermic transitions at 20°C and 43°C during the cooling stages.Scanning electron microscopy (SEM) study revealed a significant morphology changeby grafting of octadecyl chains onto the polyaniline backbone. The electrical conductivityof poly(N-octadecylaniline) that was doped with dodecylbenzene sulphonicacid (DBSA) was 8×10-4 S.cm-1 and the investigation of cyclic voltammograms (CV)showed that the electroactivity of this polymer is acceptable. The obtained polymer wascompletely soluble in non-polar organic solvents such as xylene and n-hexane. A thinflexible film of the synthesized poly(N-octadecylaniline) was prepared by casting fromn-hexane solution and the electroactivity property of the obtained film was investigatedby CV method.

Poly(butylene terephthalate) (PBT) nanofibres containing functionalizedmultiwalled-carbon nanotubes (F-MWNTs) were prepared by electrospinningtechnique. The F-MWNTs were prepared by the introduction of aromatic amine(COC6H4-NH2) groups onto their side wall via Friedel-Crafts acylation. The diameter ofneat PBT nanofibres was below 500 nm and had smooth surface. The scanningelectron microscopy (SEM) also showed that F-MWNTs/PBT composite nanofibres mathad similar morphology with that of pure PBT and without beads. The surface of thecomposite nanofibres was also smooth even by adding high quantity of F-MWNTs. TheF-MWNTs were embedded within nanofibres and well oriented along the nanofibreaxis, as confirmed by transmission electron microscopy (TEM). The mechanicalproperties (specific tensile strength and moduli) of the PBT nanofibres were significantlyenhanced by the incorporation of F-MWNTs. It was also observed that themelt-crystallization temperature (Tc) of PBT nanofibres shifted to a higher temperature(about 10°C) by the incorporation of F-MWNTs which might be due to the nucleatingeffect of the nanotubes

Poly(methyl methacrylate-co-butyl acrylate)/tetrabutylphosphonium modifiedmontmorillonite (P(MMA-co-BA)/P-MMT) composite films were prepared bysimple solution casting technique. P(MMA-co-BA) was synthesized throughsolution polymerization in the presence of benzoyl peroxide (BPO) as an initiator. Aftermodification via cation exchange reaction by tetrabutylphosphonium bromide, theorganoclay was dispersed in toluene and added into P(MMA-co-BA) solution. Thewell-dispersed mixture was cast by doctor blade technique to obtain the compositefilms. The P-MMT content in the composites was varied (i.e., 1, 2, 3 and 6 wt%) inorder to study its effects on thermal stability, mechanical properties and UV shieldingability. The structure of P-MMT in the composites was investigated by XRD technique.The composites containing 1 and 2 wt% of P-MMT showed the d001 peak slightlyshifted to lower 2θ, indicating mainly intercalated structure occurred with someagglomerations of particles. The intercalated structure of P(MMA-co-BA)/P-MMT 2%composites was observed by TEM technique. The TGA results showed thatdegradation of the composites occurred at higher temperatures compared to that oftheir virgin polymer and the degradation point increased with P-MMT content. Tensilestrength and Young's modulus of composites were higher than those of their originalcopolymer. By addition of 1-3 wt% of P-MMT, it could be seen that the higher theP-MMT loading, the higher would be the tensile strength and Young's modulus. TheP(MMA-co-BA)/P-MMT composite films showed their screening ability in UV region,especially in the UV-B range, which is rather higher than that in the visible region.

Scientists and engineers are constantly trying to improve the performance ofasphalt mixtures. Modification of the asphalt binder is one approach used toachieve good mixtures. Fibres and polymers are generally two importantmodifiers in improving pavement performance, though fibres have received muchattention for their enhancement effects among other modifiers for asphalt. In this study,therefore, polypropylene (PP) fibres were selected as fibre modifier because of theirlow-cost and consistency with asphalt pavement. Asphalt specimens were made by aSuperpave gyratory compactor (SGC), analyzed by both Marshall and Superpavemethods and tested by Marshall stability apparatus. PP Fibres of two different lengths,i.e., 6 and 12 mm were used at four different percentages of 0.1%, 0.2%, 0.3% and0.5%, by the total weight of the asphalt concrete. The dry procedure was used to blendfibres with aggregates at the optimized dosage of bitumen, i.e., 4.2%, by weight of thetotal mix. The experimental results show that adding PP fibre increases the Marshallstability (26%) and the air voids (67%) while reducing the flow (38%) properties. The"law of mixtures" was used for composite materials to study the fitness of specificgravity of the fibre-reinforced asphalt concrete mixtures with the theoreticallycalculated values. Thus, it was revealed that the fitness of the real results with thetheoretically calculated values is considerable, especially at low percentages of fibres,e.g., 0.1% and 0.2%. It became evident that the existence of voids in all modified and/orneat asphalt-concrete treatments leads samples to completely unfit with the “law ofmixtures”. Finally, the analysis of variance (ANOVA) method and Dennett's test wereused to check the accuracy of the results which significantly demonstrates theadvantages of using PP fibres in AC mixtures.

Avinyl functional microemulsion was successfully prepared via polycondensationbetween polysiloxane prepolymer and a modifier (vinyl silane coupling agentwith alkoxy groups). The polysiloxane prepolymer was prepared by ring-openingof D4 (octamethylcyclotetrasiloxane). The structure and properties of vinyl functionalmicroemulsion were characterized by transmission electron microscopy (TEM), Fouriertransform infrared (FTIR), photon correlation spectroscopy (PCS). FTIR Spectroscopyresult showed that vinyl groups were successfully introduced into the polysiloxanemolecules. The variation in pH, amount of vinyl coupling agent and catalyst werestudied in relation to the properties of the final microemulsion. The results indicated thatunder strong acidic more coagulum and higher percentage of conversion occurred inthe microemulsion. TEM results also revealed that particles are densely packed instrong acidic condition but become sparsely distributed in weak acidic condition. Anincrease in the vinyl coupling agent content leads to an increase in formation ofcoagulum and in particle size, but it lowers the particle size distribution. The smallerratio of the average surface coverage of surfactant leads to higher amount ofcoagulation which is in linear dependence to the increased amount of vinyl couplingagent modifier. Photon correlation spectroscopy results show that increasing theamount of vinyl coupling agent modifier increases the particles size, while reduces theparticles size distribution. It can be concluded that the coagulum weight fractionincreases linearly with higher amount of catalyst. An increase in the vinyl couplingagent modifier leads to an increase in the coagulum. The microemulsion showsstability when the amount of catalyst is about 3.0-4.0 wt%.

Among different types of nanoparticles, carbon nanotubes have always been thesubject of extensive studies. In the present study, the effect of concurrentpresence of multi-walled carbon nanotubes (MWNT)s and nanoclay on theelectrical and mechanical properties of an epoxy system was investigated using theultrasonic technique for dispersion of nanoparticles. First, an optimum amount for eachtype of filler is obtained in order to choose appropriate contents of clay/MWNTs componentsin nanocomposite samples. A nanocomposite reinforced with 0.5 wt% MWNTsshowed higher modulus compared with a nanocomposite enhanced with 5 wt% nanoclay,implying that a lower content of MWNTs can lead to higher Young's modulus.Moreover, it was found that the electrical conductivity could be achieved by addingMWNTs. However, addition of nanoclay to epoxy/MWNTs nanocomposite would hinderits electrical conductivity. Simultaneous presence of MWNTs and nanoclay enhancedthe Young's modulus and fracture toughness of the prepared nanocomposites.However, the tensile strength of all nanocomposites decreased except for thosereinforced with 0.5 wt% MWNTs which showed an increase of around 7%. The SEMmicrographs were used for the fractography of specimens and investigation of thedispersion state of MWNTs in the matrix. It was observed that fillers of different shapesprovide different features on the fracture surface due to different mechanisms in theirtoughening action. The X-ray diffraction (XRD) was used to determine the d-spacing ofnanoclay layers. The results showed that d-spacing of layers increased from 18.42 A to42.28 A and thus an intercalated nanocomposite was obtained.

To avoid the loss of precious metal catalysts on carriers, a simple approach isintroduced for sliver colloids having 'anchorage's hooked onto inorganicsubstrate surfaces. This method is based on the nanoreactor of solubilizedcopolymer micelles for the fabrication of Ag sphere particles. The hydrolysis of tert-butylacrylate yields acrylic acid and a tri-block copolymer polystyrene-b-poly(acrylic acid)-bpoly(γ-methacryloxypropyltrimethoxysilane) (PS-PAA-PMPS), with PMPS as activefunctional moieties, was synthesized and characterized which can play stronginteraction with inorganic substrates surface as an "anchorage". The PS-PAA-PMPScopolymer solution was prepared to solubilize metal salts to prepare nanoparticles asnanoreactors for in situ reduction. The degree of solubility increased with the increasedhydrophilic PAA units but it was also restricted by its dimensional size resistingsolubilization. Spherical particles in diameters of 10~30 nm were well dispersed andSEM images showed the hybrid silver colloids remaining on the glass substrate due totheir firm adherence after elution. It was demonstrated that this special polymerprotectedsystem provides a successful way for nanoparticles to form anchorage ontothe glass surface with firm adhesion and stable properties. This kind of silver colloidsconveniently form firm and stable coatings onto the glass substrate which might givelonger service life as catalysts to be used in electromagnetic interference shielding,anti-microbial uses and catalytic reduction of p-nitrophenol