Showing papers in "Polymer Bulletin in 2006"
TL;DR: In this paper, the phase behavior and viscoelastic properties of the poly(methyl methacrylate) (PMMA) and poly(styrene-co-maleic anhydride) (SMA) blend systems have been investigated.
Abstract: The phase behavior and viscoelastic properties of the poly(methyl methacrylate) (PMMA) and poly(styrene-co-maleic anhydride) (SMA) blend systems have been investigated. In homogeneous region, the blends of different compositions behave as a classical polymer melt. On the other hand, in phase-separated region, the blends of symmetric and off-symmetric compositions show different characteristic thermorheological responses corresponding to the different morphologies, which has been confirmed by TEM analysis and qualitatively corroborated by utilizing Palierne’s emulsion model. Except for the well-known characteristic deviations of the storage modulus at low frequencies, the curves that describe the relationships between other rheological functions such as master curves obtained through time-temperature superposition (tTS) principle, van Gurp-Palmen Plots, Han Plots, and Cole-Cole Plots, also show significantly different shapes corresponding to symmetric and off-symmetric composition. Based on these findings we propose that such characteristic fingerprints can be used not only for marking phase separation but also for inferring the resulting morphology. It is also shown that van Gurp-Palmen Plots and Cole-Cole Plots are more sensitive than other rheological functions. In addition, on comparing the validity of tTS principle in different blend systems, we argue that the morphology is responsible for whether tTS principle holds or not for polymer blend.
104 citations
TL;DR: In this paper, a protein-based superabsorbent hydrogel was synthesized and its swelling behavior was studied using FTIR spectroscopy, where the graft copolymerization of acrylic acid (AA) onto the hydrolyzed collagen as a protein backbone was carried out in a homogeneous medium.
Abstract: In this work, we synthesize a novel protein-based superabsorbent hydrogel and study its swelling behavior. The crosslinking graft copolymerization of acrylic acid (AA) onto the hydrolyzed collagen as a protein backbone was carried out in a homogeneous medium. Potassium persulfate (KPS) as an initiator and N,N′-methylene bisacrylamide (MBA) as a crosslinker were used. The product’s structure was established using FTIR spectroscopy. We were systematically optimized the certain variables of the graft copolymerization (i.e. the monomer, the initiator, and the crosslinker concentration) to achieve a hydrogel with maximum swelling capacity. Under this condition, maximum capacity of swelling in distilled water was found to be 920 g/g. Morphology of the optimized sample was examined by scanning electron microscopy (SEM). The swelling ratio in various salt solutions was also determined. Additionally, the swelling of superabsorbing hydrogels was measured in solutions with pH ranged from 1 to 13. The synthesized hydrogel exhibited a pH-responsiveness character so that a swelling-collapsing pulsatile behavior was recorded at pH 2 and 8.
90 citations
TL;DR: In this paper, thermoplastic polyetherimide (PEI)-SiO2 nanocomposites were prepared from a soluble PEI, which was synthesized from m-phenylenediamine and bisphenol A dianhydride, in combination with tetraethoxysilane solution via a novel sol-gel process.
Abstract: Thermoplastic polyetherimide (PEI)-SiO2 nanocomposites were prepared from a soluble PEI, which was synthesized from m-phenylenediamine and bisphenol A dianhydride, in combination with tetraethoxysilane solution via a novel sol-gel process. A coupling agent was used to enhance the compatibility between PEI and silica. This approach was compared with PEI-clay nanocomposite in which montmorillonite was modified with ammonium salts of 12-aminododecanoic acid using an intercalation polymerization. The size and dispersion of the silica or clay in the PEI nanocomposites were analyzed by X-ray diffractometer and scanning electron microscopy. It was found that the sol-gel process offered a fine interconnected or co-continuous phase, whereas the clay remained dispersed in nanocomposites. Though the thermal properties of PEI-clay nanocomposites were improved over pristine PEI, physical testing showed that the films become brittle as the organoclay content increased to over 2%. The thermal stability and mechanical properties of the PEI/silica nanocomposites prepared by sol-gel process were improved with silica content up to 10%. The onset decomposition temperatures were 550–600 °C. The dielectric constant decreased with increasing amounts of silica. At higher silica contents, the mechanical properties were reduced as a result of the phase separation.
87 citations
TL;DR: In this article, the enthalpy of a perfect crystal (ΔHf°) of cellulose acetate was determined using differential scanning calorimetry and wide angle X-ray scattering (WAXS).
Abstract: The enthalpy of fusion of a perfect crystal (ΔHf°) of cellulose acetate was determined in this work. In order to do so, cellulose samples from different sources were heterogeneously acetylated. The cellulose acetate samples were characterized by differential scanning calorimetry (DSC) and wide angle X-ray scattering (WAXS). The diffractograms were deconvoluted into halos and peaks using the Pseudo-Voigt peak function. From these deconvolutions, the hypothesis that best represented the two-phase model was the one in which the amorphous model was represented by the halos at 11° and 21°, considering an ordered amorphous model. The WAXS crystallinities of the samples were then calculated from these values and plotted against the enthalpy of fusion of the materials, and from this relationship the ΔHf° for the cellulose acetate was determined to be 58.8 J/g.
75 citations
TL;DR: In this paper, the properties of swelling and dye adsorption of poly(acrylamide-sepiolite) (AAm/Sep) composite hydrogel were investigated.
Abstract: Polymer-clay hydrogel composite was prepared on the basis of polyacrylamide (PAAm) gel containing the clay mineral sepiolite. The properties of swelling and dye adsorption of poly(acrylamide-sepiolite) (AAm/Sep) composite hydrogel were investigated. The parameters of swelling and diffusion in water and dye solutions were calculated for the AAm and AAm/Sep hydrogels. It was found that the equilibrium swelling degree of obtained composite higher than that of AAm gel. Spectroscopic analysis of composite and composite-dye systems was done with FT-IR method. Adsorption of monovalent cationic dyes such as Basic Blue 12 (BB-12) Basic Blue 9 (BB-9), and Basic Violet 1 (BV-1), was studied on the composite. In the adsorption experiments, S (Sigmoidal) type for composite gel adsorption isotherms in the Giles classification system was found. Adsorption studies indicated that the amounts of adsorbed dyes on the AAm/Sep composite hydrogel were increased with following order; BB-12 > BB-9 > BV-1. The composite hydrogel may be considered as good candidate for environmental application to retain more water and dyes.
74 citations
TL;DR: A novel easily processable resin, poly(dimethylsilylene ethynylenephenyleneethynylene) [-Si(CH3)2-C≡C-C6H4-C ≥C-]n terminated with phenylacetylene, was developed as discussed by the authors.
Abstract: A novel easily processable resin, poly(dimethylsilylene ethynylenephenyleneethynylene) [-Si(CH3)2-C≡C-C6H4-C≡C-]n terminated with phenylacetylene, was developed. And the properties of the resulting resin were investigated. The resin was a viscous liquid and soluble in a variety of solvents. The cured resin showed high heat-resistant stability and high char yield. The cured resin was sintered at 1450 °C and obtained sintered product was analyzed by FTIR, SEM and X-ray diffraction techniques and the results showed β-SiC were formed in the product.
68 citations
TL;DR: In this article, the microwave absorbing properties of carbon black/silicone rubber blends were investigated in the frequency range 0.2÷6.0 GHz, varying the carbon black contents.
Abstract: In this work the microwave absorbing properties of carbon black/silicone rubber blends were investigated in the frequency range 0.2÷6.0 GHz, varying the carbon black contents. In particular, the permittivity of the samples was measured by a network analyzer and then the experimental data were fitted as function of microwave frequency and carbon black content, e*=e*(f,C).
66 citations
TL;DR: In this paper, elasticity and light scattering measurements were carried out on poly(acrylamide) (PAAm) hydrogels prepared from acrylamides and N,N’methylenebisacrylide (BAAm), under various reaction conditions, and it was shown that the crosslink efficiency of BAAm exl decreases as the initial monomer concentration Co is decreased.
Abstract: Summary Elasticity and light scattering measurements were carried out on poly(acrylamide) (PAAm) hydrogels prepared from acrylamide (AAm) and N,N’methylenebisacrylamide (BAAm) monomers under various reaction conditions. Elasticity tests showed that the crosslinking efficiency of BAAm exl, that is the fraction of BAAm forming effective crosslinks decreases as the initial monomer concentration Co is decreased. At Co = 3 %, exl was found to be 10 -2 – 10 -3 , indicating that 99 to 99.9 % of BAAm used in the hydrogel preparation are wasted in elastically ineffective links. Debye-Bueche analysis of the light scattering data showed that, irrespective of the gel synthesis conditions, the correlation length ξ , that is, the extension of inhomogeneities in the hydrogels is 10 1 nm. The extent of frozen concentration fluctuations in the hydrogels represented by 2 η decreases with increasing crosslinking efficiency of BAAm. The combination of the light scattering and the elasticity data of gels shows a direct correlation between the fraction of wasted crosslinker molecules during gelation and the spatial gel inhomogeneity.
66 citations
TL;DR: In this article, amine groups were incorporated onto PHMA hydrogels by amination reaction with different diamines, and they were used as sorbent for removal of indigo carmine and Cu(II) ion, as a model dye molecule and metal ion from aqueous solutions.
Abstract: Poly(N-hydroxymethylacrylamide), PHMA, hydrogels were prepared by using N-hydroxymethylacrylamide, HMA, monomer and polyethyleneglycol(400)diacrylate as a crosslinking agent in aqueous medium and then amine groups were incorporated onto PHMA hydrogels by amination reaction with different diamines. The obtained hydrogels were characterized by determination of amine value, hydroxymethyl group content and FTIR spectra. The amine value of hydrogels changed from 2.23 to 4.64 mmol/g by depending on the amine compounds used in amination reaction. Their swelling degree increased at acidic pH values and they showed pH dependent swelling behaviour. They were used as sorbent for removal of indigo carmine and Cu(II) ion, as a model dye molecule and metal ion, respectively, from aqueous solutions. The adsorption properties of the hydrogels were investigated by depending on pH, time and initial indigo carmine or Cu(II) ion concentration. It was seen that the amine group incorporated hydrogels have quite high adsorption rate and adsorption capacity, and their adsorption capacities changed with pH of the solution. Langmuir isotherm model was the best fit for adsorption of both indigo carmine and Cu (II) ion.
61 citations
TL;DR: In this article, the effect of using two different kinds of PP-g-MA (polypropylene-grafted maleic anhydride), with graft efficiencies of 0.1 and 1.0 wt% of MA and with different molecular weight, on clay dispersion and mechanical properties of nanocomposites was investigated.
Abstract: Polypropylene-clay nanocomposites were prepared by melt intercalation in a twin screw extruder using two mixing methods: two-step mixing and one-step mixing. The effect of using two different kinds of PP-g-MA (polypropylene-grafted maleic anhydride), with graft efficiencies of 0.1 and 1.0 wt% of MA and with different molecular weight, on clay dispersion and mechanical properties of nanocomposites was investigated. Three different clays, natural montmorillonite (Cloisite Na+) and chemically modified clays Cloisite 20A and Cloisite 30B were used. The relative influence of each factor was observed from structural analysis by WAXD, TEM, and mechanical properties. X-ray diffractometry (XRD) was used to investigate the intercalation effect in the nanocomposites. The results indicted that the intercalation effect and mechanical properties, specially modulus, tensile strength and impact strength, were enhanced by increasing the content of MA, using maleated PP with higher graft efficiency, and using the two step mixing conditions. Better dispersion and exfoliation were obtained when using clay 20A than 30B and natural Na+ montmorillonite. The results showed that clay dispersion and interfacial adhesion are greatly affected by the kind of maleated PP. The increase in content of polar groups gives as a result better interfacial adhesion and subsequent mechanical performance.
60 citations
TL;DR: In this article, the authors investigated the role of the factors affecting the grafting reaction, such as solvents composition, reaction time, temperature, pH of reaction media, concentration of acrylamide and hydrogen peroxide.
Abstract: Horseradish peroxidase catalyzed grafting of acrylamide (AM) onto Kevlar fibers in mixed solvents of dioxane and water was studied. The factors affecting the grafting reaction, such as solvents composition, reaction time, temperature, pH of reaction media, concentration of acrylamide and hydrogen peroxide were examined. The modified fiber was characterized with IR, scanning electron microscopy (SEM), elemental analysis, XPS, contact angle measurement and the grafting yield. The O/C ratio and N/C ratio on the surface increased after treatment and the surface of the Kevlar fiber became rougher. The contact angle decreased from 80 to 45 after grafting, indicating the wettability of the fiber increased after modification. All the results suggested that AM have been grafted onto the Kevlar surface through HRP-mediated radical initiated grafting reaction. And the probably mechanism of HRP catalyzed grafting of AM onto Kevlar surface was proposed.
TL;DR: In this article, a side chain thioxanthone-containing polymer (PSt-TX) was synthesized and characterized by modification of polystyrene prepared by Atom Transfer Radical Polymerization.
Abstract: Side chain thioxanthone-containing polymer (PSt-TX) was synthesized and characterized by modification of polystyrene prepared by Atom Transfer Radical Polymerization. PSt-TX exhibits absorption characteristics similar to that of the unsubstitued thioxanthone. Its capability to act as initiator for the polymerization of methyl methacrylate was also examined.
TL;DR: The in vitro study of biocompatibility, carried out with the hydrogels containing different types of Bisomers, showed no evidence of cell toxicity nor any considerable hemolytic activity, so these materials have potential as drug carriers or biological glue and sealants.
Abstract: Novel poly(Bisomer/HEMA/IA) hydrogels were prepared by radical copolymerization of poly(alkylene glycol) (meth)acrylates, i.e. short chains Bisomers, 2-hydroxyethyl methacrylate (HEMA) and itaconic acid (IA) in a mixture of water/ethanol as solvent. These hydrogels were characterized in terms of swelling in conditions similar to the biological fluids (pH range 2.20–7.40 buffer solutions), compression-strain measurements, thermal properties and morphology. The influence of the type of Bisomer and of the itaconic acid on swelling and mechanical properties, as well as on morphology and thermal behavior of the resulting hydrogels, were investigated.
TL;DR: In this paper, high density polyethylene (HDPE)/montmorillonite (MMT) nanocomposites were prepared by melt blending using twin screw extruder with two-step process.
Abstract: The highdensitypolyethylene (HDPE)/montmorillonite (MMT) nanocomposites were prepared by melt blending using twin screw extruder with two step process. The master batches were manufactured by melt compounding with maleic anhydride grafted HDPE (HDPE-g-MAH) and MMT. The HPDE/MMT master batches were subsequently mixed with HDPE. The blown nanocomposite films were obtained by a single screw extruder attached film blowing and take-off unit. The MMT dispersion in the nanocomposite films was characterized by X-ray diffraction (XRD) and transmission electron microscope (TEM). The influence of MMT on the crystallinity, thermal properties and mechanical properties as a function of compatibilizer was investigated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and universal testing machine, respectively. X-ray and TEM images showed the partially exfoliated nanocomposites which have the 5:1 – 20:1 ratios of HPDE-g-MAH and MMT. The thermal and mechanical properties of nanocomposites were enhanced by increasing the contents of MMT and in the presence of compatibilizer.
TL;DR: In this article, the characterization of styrene-butadiene-styrene (SBS) block copolymers at molecular level through different techniques was dealt with, such as Gel Permeation chromatography (GPC) in tetrahydrofuran (THF) solvent and using a calibration curve based on mono-dispersed polystyrene standards; the relative molecular weights obtained by GPC were adjusted using a correction factor based on Mark-Houwink-Sakurada parameters for SBS in THF.
Abstract: This paper deals with the characterization of styrene-butadiene-styrene (SBS) block copolymers at molecular level through different techniques. SBS molecular weight distributions (MWD) were measured by Gel Permeation chromatography (GPC) in tetrahydrofuran (THF) solvent and using a calibration curve based on mono-dispersed polystyrene standards; afterwards, the relative molecular weights obtained by GPC were adjusted using a correction factor based on Mark-Houwink-Sakurada parameters for SBS in THF. Quantitative characterization of polybutadiene (PB) structures in SBS was made by solid-state 13C Nuclear Magnetic Resonance (NMR). A novel method using Fourier transform infrared spectroscopy (FTIR) has been developed for characterizing the SBS composition. This method covers the determination of composition in SBS ranging from 20 to 75 wt% of polybutadiene (PB) and was performed based on a FTIR calibration curve, which was prepared using mixtures of polystyrene (PS) and polybutadiene (PB) of known compositions.
TL;DR: In this article, a combination of differential thermal analysis (DTA), thermogravimetric (TG), wide angle X-ray diffraction (WAXD), tension testing, elemental analysis and microscopic examination was performed on polyacrylonitrile (PAN) fibers.
Abstract: Thermal stabilization of two kinds of polyacrylonitrile (PAN) fibers was studied by the combination of differential thermal analysis (DTA), thermogravimetric (TG), wide angle X-ray diffraction (WAXD), tension testing, elemental analysis and microscopic examination. The cyclization reaction in fiber P1 occurs at higher temperature with a concentrated heat release, while its incorporation of oxygen is earlier and more rapid than that in fiber P2. Skin-core structure was observed in the as-stabilized fiber of P1, but not in that of P2. During heat treatment, the stress in fiber P1 is about 20 MPa higher than that in fiber P2. The results indicate that crystallinity and content of acidic comonomers in PAN fibers are the essential property indices which influence thermal stabilization significantly. Early initiation and sufficient cyclization are important preconditions for obtaining stabilized fibers with uniform microstructure.
TL;DR: In this paper, the morphology of the hyperbranched shape memory polyurethane (HB-SMPU) films was investigated by the use of wide-angle X-ray diffraction (WAXD), atomic force microscopy (AFM), DSC and dynamic mechanical analysis (DMA).
Abstract: Hyperbranched shape memory polyurethane (HB-SMPU) were prepared from 4,4’-diphenylmethane diisocyanate, poly (butylenes adipate) glycol, and hyperbranched polyester as chain extender via a two-step process. The morphology of the HB-SMPU films was investigated by the use of wide-angle X-ray diffraction (WAXD), atomic force microscopy (AFM), DSC and dynamic mechanical analysis (DMA). It was found that the PBAG soft segments in HB-SMPU with 15–35 wt. % of hard segments were in a crystalline state, however, the PBAG segments were in an amorphous state in the HB-SMPU with 40 wt. % hard segments. The increase of the hard segment content resulted in the decrease of the melt transition temperature of the HB-SMPU. The HB-SMPU with 25 wt. % of hard segment content possessed highest loss tangent. Heat of crystallization was dependent on the content of hard segment in the HB-SMPU. 96–98 wt. % shape recovery could be obtained for the HB-SMPU with 15–35 wt. % of hard segment. The content of hard segments in HB-SMPU was very important in determining their physical properties.
TL;DR: In this paper, the combined effect of stepwise temperature, dwell time and stretching on the properties and structures of PAN fibers was studied by elemental analysis, bulk density determination, tension measurement, FTIR and WAXD.
Abstract: Thermal stabilization parameters are the key factors in the production of carbon fibers. The combined effect of stepwise temperature, dwell time and stretching on the properties and structures of PAN fibers was studied by elemental analysis, bulk density determination, tension measurement, FTIR and WAXD. It is indicated that the whole process of thermal stabilization can be roughly divided into four stages by three temperatures of 220 °C, 240 °C and 270 °C, of which the increment rate of oxygen content, as well as the bulk density of fibers, is different, while the dwell time has no obvious effect on them until about 240 °C. Stretching plays a great role on the tension in fibers at early stabilization stage, while temperature contributes more at later stage. The stretching is also helpful to suppress the growth of crystallite below 220 °C, which has not been reported in published documents.
TL;DR: In this paper, a graft copolymer was prepared by grafting acrylic acid (AA) onto hydroxyethyl cellulose (HEC) using [Ce(NH4)2(NO3)6]/HNO3 initiator system in the presence of poly(ethyleneglycol diacrylate) (PEGDA) crosslinking agent in 1:1 (v/v) mixture of methanol and water at 30 °C.
Abstract: Crosslinked hydroxyethyl cellulose-g-poly(acrylic acid) (HEC-g-pAA) graft copolymer was prepared by grafting of acrylic acid (AA) onto hydroxyethyl cellulose (HEC) using [Ce(NH4)2(NO3)6]/HNO3 initiator system in the presence of poly(ethyleneglycol diacrylate) (PEGDA) crosslinking agent in 1:1 (v/v) mixture of methanol and water at 30 °C. Carboxyl content of copolymer was determined by neutralization of –COOH groups with NaOH solution and sodium salt of copolymer (HEC-g-pAANa) was swelled in distilled water in order to determine the equilibrium swelling value of copolymer. Both dry HEC-g-pAA and swollen HEC-g-pAANa copolymers were used in the heavy metal ion removal from three different aqueous ion solutions as follows: a binary ion solution with equal molar contents of Pb2+and Cd2+, a triple ion solution with equal molar contents of Pb2+, Cu2+ and Cd2+, and a triple ion solution with twice Cu2+molar contents of Pb2+and Cd2+. Higher removal values on swollen HEC-g-pAANa were observed in comparison to those on dry polymer. The presence of Cu2+decreased the adsorption values for Pb2+ and Cd2+ ions on both types of HEC copolymer. However, with further increase in Cu2+ content both dry and swollen copolymers became apparently selective to Cu2+ removal and Cu2+ removal values exceeded the sum of adsorption values for Pb2+ and Cd2+. Maximum metal ion removal capacities were 1.79 and 0.85 mmol Me2+/gpolymer on swollen HEC-g-pAANa and dry HEC-g-pAA, respectively.
TL;DR: In this paper, the synthesis of 3-mono-O-ethyl cellulose via 2,6-di-Othexyldimethylsilyl cellulose was studied.
Abstract: The synthesis of 3-mono-O-ethyl cellulose (EC) via 2,6-di-O-thexyldimethylsilyl cellulose was studied. Treatments with tetrabutylammonium fluoride trihydrate lead to the complete cleavage of the protective group. The structure of the polymer was confirmed by means of one- and two dimensional NMR spectroscopy. 3-mono-O-EC is soluble both in aprotic-dipolar organic media and water and shows thermoreversible gelation. A gelation temperature of 58.5 °C was found, which is about 30 °C higher than the cloud point temperature of conventional water soluble EC.
TL;DR: In this article, the authors investigated the dynamic mechanical properties of hydrogenated acrylonitrile butadiene rubber (HNBR) filled with organophilic layered silicates (OLS).
Abstract: Morphologies and dynamic mechanical properties of hydrogenated acrylonitrile butadiene rubber (HNBR) filled with organophilic layered silicates (OLS) were investigated The results from transmission electron microscopy (TEM), small angle X-ray scattering (SAXS, especially X-ray diffraction on larger structures) and dynamic mechanical analysis (DMA) favor the notion of local filler-filler network-like clusters consisting of exfoliated silicate layers Especially, processing under high shear forces leads to an anisotropic structure of the network Due to the orientation of the clusters the aspect ratio (at small deformations) increases This is in accord with the large reinforcing effect observed for these materials For example, the stress at 50% elongation from tensile test can be increased at 33% with 5 phr OLS compared to the unfilled reference We estimate the activation energy of the immobilized polymer layer around the filler structures and show that the values depend on the spatial direction (the values are between 34 kJ/mol and 4 kJ/mol) As a result, the DMA–analysis could be used as a supporting method to evaluate orientation effects of the filler structures
TL;DR: In this article, super swelling acrylamide (Am)/N-vinylpyrrolidone (NVP)/3-(2-hydroxyethyl carbamoyl) acrylic acid (HECA) hydrogels were prepared by free radical polymerization of quaternary mixtures of Am, NVP, HECA and water.
Abstract: Super swelling acrylamide (Am)/N-vinylpyrrolidone (NVP)/3-(2-hydroxyethyl carbamoyl) acrylic acid (HECA) hydrogels were prepared by free radical polymerization of quaternary mixtures of Am, NVP, HECA and water. The hydrogels were used in experiments on swelling, diffusion and adsorption of some water-soluble monovalent cationic dyes such as Crystal Violet (CV), Malachite Green (MG) and Methylene Blue (MB). In the experiment of the adsorption of dyes from their aqueous solutions type-S adsorption isotherm were found. The diffusion of water within the hydrogel was found to have non Fickian character. The uptake of dyes within the hydrogel increased in the following order: MG > MB > CV. The binding ratio of the hydrogel/dye systems was gradually increased with the increase of HECA content in the AAm/NVP/HECA hydrogel.
TL;DR: In this paper, the influence of chemical polymerization conditions on the yield and thermal behavior of PANI doped Dodecylbenzensulfonic (DBS) was studied by means of a 24 factorial experimental design.
Abstract: Influence of chemical polymerization conditions on the yield and thermal behavior of PANI doped Dodecylbenzensulfonic (DBS) was studied by means of a 24 factorial experimental design. These conditions included temperature, concentration of dopant, concentration of oxidant and stirring rate. It was found that the thermogravimetric behavior was not sensitive to any of the conditions tested. By contrast, the yield was dependent on three of the variables studied. For 10 mmol of aniline, the maximum yield was obtained when temperature, concentration of dopant, concentration of oxidant and stirring rate were 25 °C, 27 mmol, 11.5 mmol and 500 rpm, respectively. The most important effects on the yield are the main effect of oxidant (APS), the interaction dopant concentration-stirring rate and the three-factor interaction effect of dopant concentration-oxidant concentration-stirring rate. The prediction equation is:
TL;DR: In this article, the qualitative content of TiOTi group and TiOH was monitored by FTIR spectrum, and the thermal stability and film surface were characterized by TGA, DSC and AFM, respectively.
Abstract: UV curable, transparent acrylic resin/titania organic–inorganic hybrid films were prepared by controlled hydrolysis of titanium tetrabutoxide (TTB) in Span85/Tweeen80 reverse micelles and subsequent in situ photopolymerization of acrylic monomers. The qualitative content of TiOTi group and TiOH was monitored by FTIR spectrum, and the thermal stability and film surface were characterized by TGA, DSC and AFM, respectively. TGA data show that TiO2-hybrid films can upgrade the decomposition onset temperature and the temperature at which there is a maximum mass loss rate (Tmax). DSC data show that prolonged exposure to UV light and post-thermal treatment can decrease the Tonset and Tpeak of the exothermal peak and the condensation temperature between TiOH, and increase ΔH of the exothermal peak. FTIR spectra show the presence of two νs(COO-) modes with the νa-νs splitting magnitude (Δν∼87 cm-1 and 148 cm-1, respectively), suggesting that acrylic acid acts as a bidentate coordination mode and therefore chemical linkages exist between inorganic and organic phases. AFM phase images showed the presence of inorganic domains, with mean size of 21.6 nm–28.8 nm, were uniformly dispersed in the polymeric networks.
TL;DR: In this paper, a thermally initiated free radical precipitation polymerization in ethyl acetate was investigated, and the structure and morphology of the microparticles were evaluated using Fourier transform infrared spectroscopy and scanning electron microscopy.
Abstract: Microparticles composed of (meth)acrylic acid, potassium (meth)acrylate, and trifunctional pentaerythritol were prepared using a thermally initiated free radical precipitation polymerization in ethyl acetate The particle synthesis method was investigated, and the structure and morphology of the microparticles was evaluated using Fourier transform infrared spectroscopy and scanning electron microscopy Results indicate that the physicochemical properties of the microparticles are dependent on the crosslinking ratio and type of carboxylic acid monomer employed in the polymerizations The glass transition temperature behavior is significantly affected by the monomer type and the amount of crosslinking agent employed The swelling dynamics of the microparticles are also pH, monomer, and crosslinking ratio dependent
TL;DR: In this article, a large-scale polyaniline nanorod was synthesized by one-step electrochemical deposition on aluminium electrode without the aid of any templates, and the morphologies and molecular structures of the film were characterized by field-emission scanning electron microscopy (FE-SEM), UV-vis and Fourier transform infared (FTIR).
Abstract: Large-scale of oriented Polyaniline nanorods have been synthesized by one-step electrochemical deposition on aluminium electrode without the aid of any templates. The diameters and lengths of polyaniline nanorods are in the range of 50–60 nm and 150–250 nm, respectively. The morphologies and molecular structures of the film are characterized by field-emission scanning electron microscopy (FE-SEM), Ultraviolet-Visual (UV-vis) and Fourier transform infared (FTIR). The effects of synthetic parameters, such as the concentration of aniline and electric current intensity, on the morphologies of polyaniline films are investigated.
TL;DR: In this article, the I-V characteristic curves for both pure and doped polypyrrole were found to be linear and the dependence of conductivity on temperature, in order to understand the application of these systems.
Abstract: Pure polypyrrole and polypyrrole in salt form were synthesized using NaOH as reducing agent in aqueous HCl, respectively. Electrical conduction in these pure and doped polypyrrole samples was studied through the I-V characteristics of these materials. I-V characteristic curves for both pure and doped polypyrrole were found to be linear. The conductivity of chlorine-doped polypyrrole is about 104 times that of pure polypyrrole. An attempt has been made to study the dependence of conductivity on temperature, in order to understand the application of these systems. It has been observed from the variation of conductivity vs. temperature curve in both the samples that the conductivity increases with the increase in temperature. This behaviour is indicative of semiconducting nature of the samples with a variation in electrical conductivity of each, which is a strong function of doping and temperature of the environment. Activation energies for both the samples have been found to be in millielectron-volt range, 101.94 meV and 121.68 meV for pure and doped polypyrrole, respectively. An effort has also been made to understand the charge transport in these conductive polymers through models.
TL;DR: Glycidyl methacrylate (GMA) random copolymers were synthesized by solution free radical polymerization, at 70±1 °C using α,α'-azobis(isobutyronitrile) as an initiator as mentioned in this paper.
Abstract: Glycidyl methacrylate (GMA) random copolymers with methyl acrylate (MA), ethyl acrylate (EA), n-butyl acrylate (BA), methyl methacrylate (MMA), ethyl methacrylate (EMA) and n-butyl methacrylate (BMA) were synthesized by solution free radical polymerizations, at 70±1 °C using α,α’-azobis(isobutyronitrile) as an initiator to give the copolymers I – VI in good yields. The copolymer compositions were obtained using related 1H NMR spectra and the polydispersity indices of the copolymers determined using gel permeation chromatography (GPC). Tris(trimethylsilyl)methyl (Tsi=trisyl) groups were then covalently attached to the obtained copolymers as side chains by ring opening reaction between excess of TsiLi and expoxide groups of GMA units to give the copolymers ITsi – VITsi in good yields. In the coupling reaction, the TsiLi reacted selectively with the epoxy groups of the backbone polymer rather than with the carbonyl groups of the backbone. This method of preparing functionalized silanes is limited by the readiness with which TsiLi abstracts a proton, if one is available, rather than attacks at carbon. In addition in the reaction with epoxides, the product alkoxide can transfer a silyl group from carbon to oxygen or ring opening polymerization. However these were shown not to occur at the conditions of interest here. The epoxy group possesses a higher reactivity for the TsiLi than the ester and chloromethyl groups. The ring opening reaction between the epoxy group and the TsiLi is simple and fast. All the resulted polymers were characterized by FT-IR and 1H NMR spectroscopic techniques. The glass transition temperature (Tg) of all copolymers was determined by differential scanning calorimetry (DSC) apparatus. All the polymers containing trisyl groups showed a high glass transition temperature in comparison with unmodified copolymers (I – VI). Attaching the tris(trimethylsilyl)methyl group to macromolecular chain should lead to important modifications of polymer properties such as gas permeability and perm selectivity parameters.
TL;DR: An aliphatic polycarbonate, terpolymer of carbon dioxide, propylene oxide and e-caprolactone(PPC-CL-PPO-CL), was synthesized by using a polymer supported bimetallic complex as a catalyst as discussed by the authors.
Abstract: An aliphatic polycarbonate, terpolymer of carbon dioxide, propylene oxide and e-caprolactone(PPC-CL-PPO-CL),was synthesized by using a polymer supported bimetallic complex as a catalyst.The terpolymers prepared were characterized by FTIR, 1H NMR, 13C NMR, DSC and WAXD measurements. The influences of various reaction conditions such as molar ratio of the monomers, reaction time and reaction temperature on the terpolymerization progress were investigated. The results showed that e-caprolactone (e-CL) was inserted into the backbone of poly(propylene carbonate)-poly(propylene oxide) (PPC-PPO) successfully. The viscosity and glass transition temperature of the terpolymers were much higher than PPC-PPO. e-Caprolactone offered an ester structural unit that gave the terpolymers remarkable degradability. And the degradation rate of the backbone increased with the e-CL inserted into the terpolymers.
TL;DR: Chitosan membranes of three types: i) dried in ammonia atmosphere (CSA), ii) double layer crosslinked with glutaraldehyde (CSG), and iii) prepared from aqueous-ethanolic solution and dried in the presence of ammonia vapor (CSE) were developed by casting chitosans solutions onto a glossy paper used as a support in the process of filtration under high pressures as mentioned in this paper.
Abstract: Chitosan membranes of three types: i) dried in ammonia atmosphere (CSA); ii) double layer crosslinked with glutaraldehyde (CSG); and iii) prepared from aqueous-ethanolic solution and dried in the presence of ammonia vapor (CSE) were developed by casting chitosan solutions onto a glossy paper used as a support in the process of filtration under high pressures. All the membranes were characterized by infrared spectroscopy, scanning electron microscopy and by permeation experiments. Addition of ethanol to the chitosan solution decreased the time of membrane preparation and of the filtration process. The performance (solute rejection) of these membranes was found to be efficient with organic compounds such as methylene blue, truncated hemoglobin and bovine serum albumin (BSA) with molecular weights of 319.8 Da 17.7 kDa and 66.4 kDa respectively, since it retained practically 100% of the sample.