Iranian polymer journal
Volume:19 Issue: 11, 2010

The technology of opto-electronic polymer thin film deposition has advanceddramatically during the past 20 years. This advancement was driven primarily bythe need for new products and devices in the electronics and optical industries.Increasingly complex tasks are performed by computers, requiring more and morememory capacity as well as faster and faster processing speeds. This leads to aconstant need to develop high performance opto-electronic thin film materials, whichcan be used for the preparation of more highly integrated microchips. The rapidprogress in solid-state electronic devices would not have been possible without thedevelopment of new thin film deposition processes and superior thin film qualities.Among the broad variety of accessible alternatives, plasma organic polymer film hasbeen one of the most widely studied materials due to its outstanding and promisingmechanical and physicochemical properties. In this review, the new opto-electronicpolymer thin films deposited by glow discharge plasma technique in recent years isintroduced and discussed in combination with our research results. In particular, wefocus our attention on the opto-electronic properties of these polymer thin films, suchas dielectric property, electric conductivity, non-linear optical property,photo(electro)luminescent property and optical band gap. The correspondingdeposition methods of the opto-electronic polymer thin films including plasmapolymerization deposition, plasma-enhanced chemical vapour deposition are alsoreviewed within their respective sections. In summarizing the review, the development,potential applications and future directions of opto-electronic polymer thin filmsdeposited by glow discharge plasma technique are discussed, especially the filmproperties required for applications in opto-electronic devices

The ionic liquid of 1-butyl-3-methyl-imidazolium bromide ([BMIM]Br) was used asa good solvent to dissolve polyacrylonitrile (PAN). In order to systematically studythe rheological properties of PAN/[BMIM][Br] solutions, the shear rheology ofPAN/[BMIM][Br] solutions with a concentration range of 3.0-6.0 wt% was investigatedby measuring the complex and dynamic moduli at different temperatures. The effectsof solution concentration and temperature on the complex viscosity of PAN/[BMIM][Br]solutions were studied. The solutions exhibited shear-thinning behaviours. Thecomplex viscosity of solutions increased with increase in solution concentration. Theheightening of solution temperature lowers the complex viscosity of the solution. Thenthe storage modulus, G′, and loss modulus, G′′, influenced by the PAN concentrationare discussed. Both G′ and G′′ are increased with the increasing in PAN concentration.The crossover frequency of G′ to G′′ is shown to decrease as the concentration isincreased. Master curves are generated for complex viscosity by employing Carreauand Cross models to fit the experimental data. Both Carreau and Cross models yieldgood shifted curves for the complex viscosity. The activation energy for each solutionconcentration was calculated from the Arrhenius plots of the shift factors with respectto temperature. The activation energy for PAN/[BMIM][Br] solutions varies between4.79 and 8.88 kJ/mol, being slightly higher for the Cross model. The activation energyis increased with the increase in PAN concentration. It can be summarized that 3-5 wt%range of PAN/[BMIM][Br] solution concentrations are considered as dilute solutions, inwhich PAN molecules are independent of each other without any intermolecularentanglement.

Nylon short fibres were incorporated in NR/SBR rubber matrix with and without abonding system on a two-roll mill mixer. A dry bonding agent consisting ofresorcinol, hexamethylene tetramine and hydrated silica (HRH) was chosen asthe interfacial-bonding agent for this composite system. The effect of bonding agentcontent on the microstructure, mechanical and morphological properties of thecomposites was investigated. Samples were vulcanized at 150°C using a hot pressafter determination of the curing characteristics. The cure and scorch times of thecomposites decreased with increasing bonding agent concentration, while themaximum torque values showed an increasing trend. The bonding agent not onlyprovided a shorter curing time but also enhanced the mechanical properties of thecomposite. The scanning electron microscopy (SEM) of the composite fracturesurfaces implied that the presence of bonding agent has led to the breakage of fibresand less dark holes indicating the pull out of fibres without bonding agent. The resultsof anisotropic swelling studies, carried out to analyze fibre/matrix interactions andalso orientation of the fibres, showed that the restriction to swelling is higher for thecomposites containing bonding agent. Furthermore, the preferential orientation of thefibres was observed to be in the milling direction. For composites prepared with shortfibres and different loading levels of bonding agent, the dependence of the storagemodulus (G') on angular frequency followed a clear non-terminal behaviour.

Using a dope comprised of polyethersulphone (PES):N,N-dimethylacetamide:diethylene glycol (DEG) 17:43:40 (wt%), micro-porous PES hollow fibre membraneswere prepared by non-solvent vapour-induced phase separation (VIPS).The effects of bore fluid solution composition, coagulation bath temperature, air-gapdistance and humidity on the morphologies of micro-porous PES hollow fibremembranes were investigated. Light transmission microscopy was used to determinethe precipitation rate during VIPS stage as well as during non-solvent liquid-inducedphase separation (LIPS) stage. The mean pore radius of PES hollow fibre UFmembranes with sponge-like structures could be calculated by Image software fromthe SEM images. The mean pore radius of outer surface was about 0.1 μm (0.092 ~0.131 μm, PES3 ~ PES14) while the mean pore radius of the inner surface of PEShollow fibre membranes was 0.051-0.064 μm (PES12 and PES14). Pure waterpermeation fluxes and rejections were closely related to both the inner and outer skinlayers. When inner and outer surfaces possessed open structure, the pure waterpermeation fluxes increased, whereas rejections decreased accordingly. PES hollowfibre membranes with pure water permeation flux from 387 to 1210 L.m-2.h-1.bar-1 aswell as rejection of 10.1%-98.1% could be achieved by adjusting air humidity,air-gap distance and composition of bore fluid solution. Pure water permeationfluxes of PES12, PES13 and PES14 with sponge-like structures were higher than1000 L.m-2.h-1.bar-1 and their BSA rejections were only about 10%.

Anew diamine monomer containing pyridine and amide units was prepared via twostep reactions. Nucleophilic chloro-displacement reaction of 2,6-diaminopyridinewith 4-nitrobenzoyl chloride in the presence of propylene oxide afforded 2,6-bis(4-nitrobenzamido)pyridine and subsequent reduction of the nitro groups led to 2,6-bis(4-aminobenzamido)pyridine. The diamine was reacted with aromatic dianhydridesincluding pyromellitic dianhydride, benzophenone tetracarboxylic dianhydride, andhexafluoroisopropylidene diphthalic anhydride to form polyimides via two-step polycondensationmethod, and formation of poly(amic acid) followed by chemicalimidization. All the prepared materials and polyimides were fully characterized bycommon spectroscopic methods and elemental analysis. Physical and thermal propertiesof the polymers including solubility, inherent viscosity, thermal behaviour andthermal stability were studied and structure-property relations in these polyimides wereinvestigated. The inherent viscosity of the polyimides in NMP at a concentration of 0.5g.dL-1 at 30°C was between 0.47-0.51 dL/g. The polymers showed high thermalstability while their solubilities were improved. The glass transition temperatures (Tg) ofthe polymers were about 244-283°C. The 10% weight loss of polymers as a maincriterion for their thermal stability was about 420-453°C. Char yield of the polymers at600°C was in the range of 49-71%. High thermal stability resulted from incorporation ofimide backbone, phenylation of chain, symmetry of structures to avoid the weaklinkages. The polymers revealed good solubility in dipolar aprotic solvents such as Nmethyl-2-pyrrolidone, N,N-dimethylacetamide, dimethylformamide, dimethylsulphoxideand also m-cresol. Improved solubility was attributed to the presence of pyridine polarunit and amide structures in the polyimide backbones

The reaction conditions employed for the synthesis of biodegradable polymers viacoordinated anionic ring opening polymerization (CAROP) can be very differentand may result in differences between the target and actual product molarmasses. Influence of three parameters, monomer (ε-caprolactone) concentration,initiator/catalyst molar ratio, monomer/initiator molar ratio, on real polymer molar masshas been studied. Our modelling embodied a mathematical equation through which wecalculated the initiator/catalyst (alcohol/stannous 2-ethylhexanoate) ratio for all givenmonomer concentrations and targeted molar masses of the polymers. We haveestablished that in order to synthesize a polymer of certain molar mass, a lower amountof catalyst would be required when higher monomer concentrations are used. Theamount of catalyst required was found to decrease as the target molar mass ofthe polymer increases. This reduction becomes sharper with increasing monomerconcentration. For example, the initiator/catalyst ratios of 33, 24 and 10 are needed tosynthesize polycaprolactones with molar masses of 10,000, 20,000 and 50,000 Daaccordingly at monomer concentration of 1 mol/L. The initiator/catalyst ratio of 40 isless subjected to the influence of monomer concentration and may be used tocalculate the universal amount of catalyst required for the synthesis of polymers with aparticular molar mass by ring opening polymerization. The proposed mathematicalmodel was confirmed by syntheses of polymers with different molar masses andinitiators.

Ethylene polymerization with MgCl2/TiCl4/TEAl, as a Ziegler-Natta catalyst, wascarried out by slurry and gas phase processes. This catalyst was synthesizedwith a deliberate morphology by controlling the rate of recrystallization. Theparticle size distribution of the catalyst was very narrow which provided good stabilityin the reactor. The effects of temperature, monomer and hydrogen partial pressureon the catalyst activity and its deactivation coefficient were evaluated. The kineticparameters such as deactivation rate coefficient and activation and deactivationenergies were determined for both processes. It was found that deactivation ratecoefficient decreased by increased temperature of maximum 70°C, while it decreasedbeyond this temperature. The initial rate of reaction in slurry and gas phase ethylenepolymerizations increased by increasing the reaction temperature to maximum 80°Cand in comparison, at longer reaction times (>20 min) it showed a drop with maximumreaction temperature of 70°C. It was also found that the deactivation rate coefficient ofgas phase polymerization decreased by increasing the partial pressure (concentration)of hydrogen. The catalyst productivity for slurry phase polymerization of ethyleneincreased by increasing the Al/Ti molar ratio as high as 90 and beyond this ratio thecatalyst productivity dropped for the same polymerization