Iranian polymer journal
Volume:20 Issue: 7, 2011

Host/guest properties of acrylonitrile/acrylic acid copolymer (P(AN/AA)) film withvarious contents of acrylic acid (AA) were examined on dendrigraft/dyecomplexes in a divergent synthetic route. The reactions were performed onP(AN/AA) films containing 5, 10 and 20 mol% acrylic acid in feed. The products wereanalyzed using 1H NMR, FTIR, UV-visible spectroscopy, density determination,acidimetric titration, staining and transfer printing. The results showed that for the filmsbased on three different amounts of acrylic acid, the relatively higher acid contentshowed a lower rate of conversion due to the reduced steric hindrance. Furthermore,the dyes were used to probe the structure of dendrigraft on the P(AN/AA) film. Stainingwith methylene blue showed the interaction with the exterior end groups; while printingwith disperse dyes as guest molecules may illustrate the effectiveness of the hollowinterior spaces. In the trend of dye uptake and density versus generation numbers, theemerging maximum dye uptake and minimum density in the first generation confirmedthat a ''dense shell'' dendritic structure is being formed. Also, the effects of acrylic acidcontent and the steps number in dendrigraft structure are explained on the basis offilms characteristics with reference to the dendrigraft architecture.

Electrospinning technique was developed for the fabrication of poly(vinyl alcohol)(PVA)/oxidized starch (OS) fibres with applied voltage of 11 kV and tip-tocollectordistance (TCD) of 12 cm. The morphology and structure of theas-prepared fibres were well investigated by scanning electron microscopy (SEM),Fourier transform infrared (FTIR), X-ray diffraction (XRD) and differential scanningcalorimetry (DSC). SEM Photographs indicated that the morphology and diameter ofthe fibres were clearly affected by weight ratio of PVA/OS and its solutionconcentration. By lowering the weight ratio of PVA/OS and the solution concentration,the average diameter of fibres was dropped. When the weight ratio of PVA/OS wasbelow 1:3, the fibres were irregular and interspersed with shuttle-shape beads. In thisrespect, the lower the weight ratio the more beads were formed. When the solutionconcentration (weight ratio of PVA/OS 1:2) was below 18% (by weight), the fibres wereuneven and interspersed with shuttle-shape, and again the lower the concentration, ledto more beads formation. It may be noted that, the electrospinning process was hardto be performed for the solution concentration above 20% (by weight). The FTIR testsimplied that hydrogen bonds were formed between the molecular OS and PVA in thePVA/OS fibres. XRD Patterns showed that the blending with OS or high-voltageelectrostatic field during electrospinning destroyed PVA crystallinity. The DSC testsshowed that the Tg of the PVA/OS fibres was lowered and so did the thermal stabilitywith increased OS content. The PVA/OS fibres may be used in tissue engineering,wound dressing, drug delivery as a new potential material because of its non-toxic,solubility and biodegradability.

Raspberry-like ZnS nanoparticles were synthesized by hydrothermal method.ZnS particle size varies by controlling the amount of comb polycarboxylic acidsurfactant and polystyrene (PS) template. The products were characterized byX-ray diffraction (XRD), scanning and transmission electron microscopy, and Fouriertransformed infrared spectroscopy. Optical properties were investigated via UV-vis andphotoluminescence spectrophotometry. All samples consisted of ZnS cubic phase(sphalerite). The XRD patterns showed that surfactant has a vital effect on crystallitesize reduction. In contrast, PS template enhanced the growth rate of ZnS nanoparticles.Studies on morphology and particle size showed that increasing the amountof surfactant content causes the ZnS particle size to decrease to nanometric range.Although particle size increased by deposition of ZnS nanoparticles on the surface ofPS template, the uniformity of the particles increased considerably. A narrow range ofparticle size distribution (110-150 nm) was shown in the sample synthesized in thepresence of both surfactant (2.2 g/L) and PS template (1 cc of 2.7% w/v). The blueshift of absorption edge in UV-vis spectra with an increase in surfactant contentdemonstrated the quantum confinement effect of ZnS nanoparticles. The obtained ZnSnanoparticles displayed blue emission peaks at 400 and 425 nm. Furthermore, aschematic model is proposed illustrating ZnS formation on the surface of PS templatein the presence of the anionic surfactant.

The novel macromolecular copolymers of polystyrene-b-poly(2-hydroxyethylacrylate) (PS-PHEA) and polystyrene-b-poly(2-hydroxyethyl acrylate)-b-poly(γ-methacryloxypropyltrimethoxysilane) (PS-PHEA-PMPS) were synthesized asmacromolecular coupling agents via atom transfer radical polymerization (ATRP). Thesynthetic products were characterized by gel permeation chromatography (GPC) andFourier transform infrared spectroscopy (FTIR). The polystyrene (PS) block wasselected to entangle with homopolymer matrix and form strong interactions with thematrix due to its compatibility potential with the resins. The poly(2-hydroxyethylacrylate) (PHEA) block is acted as a flexible interlayer and supports some activegroups to react with fibres and introduce functional groups. The block poly(γ-methacryloxypropyltrimethoxysilane)(PMPS) provides silicon hydroxyl to react with fibres. Basaltfibres (BF) were modified by a commercial silane coupling agent and macromolecularcoupling agents, respectively, to improve the poor interfacial compatibility between thefibres and polystyrene. The FTIR confirmed the grafting of the coupling agent on thefibre. The interaction property of fibres and polystyrene was analyzed by the microdroplettest. The interfacial shear strength (IFSS) values verified that the interactionbetween the fibre and polystyrene modified with the macromolecular coupling agentwas much stronger than that with a normal silane as coupling agent. The di-blockcopolymer modified composites showed the best improvement in interfacial adhesion.The fibres were treated with 5% PS-b-PHEA solution and reacted at 120°C for 24 hwhich were considered as an optimal condition for the BF/PS system. The fracturesurfaces of the composites before and after treatment were also observed usingscanning electron microscopy (SEM). The results proved that the di-block PS-b-PHEAcan be used as a good coupling agent for the fibre and polymer composites.

The synthesis, characterization and thermal behaviour of methacrylic and acryliccopolymers of glycidyl methacrylate without and with indole groups are reported.The copolymers based on glycidyl methacrylates belong to the potential class offunctional polymers. Random copolymers of glycidyl methacrylate with methylmethacrylate, ethyl methacrylate and ethyl acrylate were synthesized by free radicalpolymerization using α,α’-azobisisobutyronitrile as initiator at 70±1°C. The copolymerproducts of glycidyl methacrylate have been modified by incorporation of indole groupsthrough the ring opening reaction of the epoxy groups. Chemical modification wasdetermined by 1H NMR and IR spectroscopic techniques. The modification ofpolyglycidyl methacrylate was faced with limited conversion which has been attributedto the steric hindering effect of the earlier grafted moieties. The glass transitiontemperature (Tg) of all copolymers was determined by dynamic mechanical thermalanalysis. The Tg value of methacrylate copolymers containing indole groups was foundto be decreased with incorporation of indole groups in polymer structures, while itincreased in indole-incorporated acrylate copolymer. The presence of indole groups inthe polymer side chains created new polymers with novel modified properties that mayfind some applications in polymer industry.

Poly(vinyl chloride) (PVC)/acrylonitrile butadiene rubber (NBR)/organoclay(Cloisite 30B) nanocomposites have been prepared via direct melt mixing in aninternal mixer. The application of Taguchi method for reducing cost andimproving properties in NBR/PVC nanocomposites is reported. Processing parameterssuch as temperature, rotor speed and mixing time have been verified in relation to themechanical properties of nanocomposites. The relative magnitude of each specificfactor, interactions between all possible combinations of two factors and theperformance estimation at any arbitary condition are also determinded. Theexperimental data are compared with the estimated data obtained by Taguchi methodto examine the accurancy of the predicted values. The structures of nanocompositeshave been characterized by X-ray diffraction, scanning electron microscopy and smallamplitude oscillatory shear rheometry. X-Ray diffraction results show that theinterlayer spacing is significantly influenced by processing conditions. The study oflinear viscoelastic properties shows that storage modulus (G') and complex viscosity,|η*|, are very sensitive to the microstructure of the nanocomposite. Dynamicalmechanical analysis of NBR/PVC nanocomposite samples has been investigated aswell. The results confirm that the Taguchi method is a useful tool for estimating themechanical properties of NBR/PVC nanocomposites.

The radical polymerizations of acrylamide (AM) and N,N'-dimethyl acrylamide(DMAA) were carried out in the presence of combined Lewis acids of AlCl3-FeCl2system. Comparing with the polymerization produced in a single Lewis acidsystem of AlCl3 or FeCl2, the AM polymerization catalyzed by a combined AlCl3-FeCl2composite in CHCl3 produced a polymer with higher isotacticity (m = 36%). The DMAApolymerization in the presence of AlCl3-FeCl2 composite produced a polymer of higherisotacticity (m = 83%) in CHCl3 and a much higher isotacticity (m = 91%) in toluene.The molecular weight and polydispersity of PAM and PDMAA show identical resultswhether polymerized in the presence or absence of Lewis acids. The combined Lewisacids showed great isotacticity in a lower polar solvent and the stereochemistry of thepolymerization was clearly affected by the molar ratio of combined Lewis acids (AlCl3-FeCl2). The polymerization of AM in the presence of 0.03-0.03 mol/L AlCl3-FeCl2composite system gave a polymer with dyad tacticity of 59/41 (m/r), the polymerizationof DMAA in the presence of 0.015-0.015 mol/L AlCl3-FeCl2 composite system gave apolymer with dyad tacticity of 95/5 (m/r). Furthermore, the isotactic specificity ofcombined Lewis acids on AM and DMAA were also influenced by aging temperatureand aging time. The optimum aging temperature of polymerization was 80°C, and theoptimum aging time was 1 h.

Structural composite latex particles were prepared via a two-stage emulsion polymerization.In the first stage, partially cross-linked poly(n-butyl acrylate) (PBA)cores were prepared, and in the second stage, a poly(vinyl acetate-co-methylmethacrylate) abbreviated as P(VAc-co-MMA), shell was grafted onto the rubber cores.In this case, a starved feed of shell monomer(s) was applied to avoid further formationof secondary particles in the aqueous phase. The effects of shell chemical compositionand MMA/VAc ratio, on the characteristics and morphology of the resulting emulsionparticles have been investigated. The resultant particles were characterized bydynamic laser light scattering (DLLS), transmission electron microscopy (TEM) anddifferential scanning calorimetry (DSC). TEM Micrographs showed that, the increase ofmethyl methacrylate (MMA) content level in the shell structure of above 50% (byweight) led to composite latex particles with more separated core and shell regions. Inaddition, the structural rubber particles with various shell structures were used totoughen the cured styrene/unsaturated polyester alkyd (ST/UPA: 75/25) resin. Theresults showed that the incorporation of rubber core-shell structured particles withVAc/MMA (50/50 wt/wt) copolymer shell improved the impact fracture energy of theST/UPA resin (UP) considerably. Scanning electron microscopy (SEM) and TEM micrographs revealed dispersed particles as singlet inside the above blend sample, whichshowed the highest impact fracture energy. Further increase of MMA units of above50% (by weight) in the shell composition resulted in significant increase in rubberparticles agglomeration as big clusters within the UP matrix. However, the particle shellcomposition and subsequently the particle/resin interfacial adhesion seem to have acrucial role on the dispersion state and toughening efficiency of the rubbery particlesinside the UP matrix.