bluuebunny/crossref_metadata_2025_split huggingface dataset:
Second harmonic generation and photochromic grating in guest-host polymer system containing azo amide chromophores
Authors: K. Marański , S. Kucharski , E Ortyl , R. Janik , J.-M. Nunzi , S. Ahmadi-Kandjani , R. Barille 
Published: August 2014

AbstractThe azo sulfonamide chromophores containing long aliphatic chain were used as active nonlinear optical (NLO) materials in films prepared by spin-coating on glass surfaces. The sulfonamides were: N-{4-[{4-[(pyrimidin-2-ylamino)sulfonyl]phenyl}diazenyl]phenyl} decanamide (Amid P); N-{4-[{4-[(1,3-thiazol-2-ylamino)-sulfonyl]phenyl}diazenyl]phenyl} decanamide (Amid T) and N-{4-[(4-nitrophenyl)-diazenyl]-phenyl}undec-10-enamide (Amid N). The host matrix was a copolymer of methyl and butyl methacrylate. The formation of diffraction grating by the guest-host system was successful only in the case of Amid N. The pitch and amplitude of the grating was 930 nm and ca. 45 nm, respectively. Quantum chemical calculations revealed that the chromophores were moderate NLO-fores showing static β values of ca. 110-130 m4/V. Two procedures were involved to align chromophores to determine first order NLO susceptibility: a) corona poling, and b) all-optical poling. The NLO coefficient d33 determined in corona poled film was 25.2, 28.6 and 93.2 pm/V for Amid P, T and N, respectively.
L-Lactide polymerization by calix[4]arene-titanium (IV) complex using conventional heating and microwave irradiation
Authors: Frediani Marco , Sémeril David , Matt Dominique , Rizzolo Fabio , Papini Anna Maria , Frediani Piero , Rosi Luca , Santella Marco , Giachi Guido 
Published: August 2014

AbstractSince the first contributions by Gedye and Giguere in 1986, growing attention has been registered on the use of microwave heating in organic synthesis. However still many aspects need to be clarified especially about the so called “microwave effect” and the possible degradation phenomena that may be recognized during polymer synthesis. In this work the complex cone-25,27- dipropyloxy-26,28-dioxo-calix[4]arene titanium (IV) dichloride (1) has been tested for the ring opening polymerization of L-lactide, comparing the effect of conventional heating with a possible microwave assisted strategy. The polymers obtained were fully characterized (NMR, IR, HPLC-SEC, DSC, MALDI-TOF and WAXD analysis). As expected the use of microwave irradiation induced an increase of the polymerization rate. On the other side the use of microwaves resulted in a slight loss of the control over molecular weight and molecular weight distribution if compared with a conventional thermal treatment.
Preparation and properties of polyurethane foams from hydroxypropoxy derivatives of urea and isocyanates
Authors: Zarzyka-Niemiec Iwona , Rydel Katarzyna 
Published: August 2014

AbstractThe products of hydroxyalkylation of N,N’-bis(2-hydroxypropyl)urea (BHPU) with large molar excess of propylene carbonate (PC) posses enhanced thermal stability. These products and 4,4’-diphenylmethane diisocyanate were used as substrates for obtaining rigid polyurethane foams, which had high thermal stability and low water uptake.
Charge storage and mechanical properties of porous PTFE and composite PTFE/COC electrets
Authors: Ko Wen-Ching , Tseng Chien-Kai , Wu Wen-Jong , Lee Chih-Kung 
Published: August 2014

AbstractRecent futuristic applications of flexible electret loudspeakers have garnered much interest for these novel loudspeakers. To increase the loudspeaker properties, a processing method was developed to improve the electret and mechanical properties of porous PTFE film. Taking a thin porous PTFE film as the base material, a cyclic olefin copolymer (COC) was coated to a base material to form a PTFE/COC composite film. Results show that the composite material improves the advantageous characteristics when used as an electret diaphragm for loudspeakers. By measuring the surface potential decay and the elastic modulus, properties of a standard porous PTFE film were compared to an improved composite PTFE/COC film. Experimental results showed that the composite PTFE/COC possess the following advantages: (1) 80% higher surface potential after 10 days at room temperature, (2) a better thermal resistance of charge storage, and (3) a 643% higher elastic modulus. Therefore, our novel composite material can be used to create a much improved electret diaphragm for flexible electret loudspeakers.
Optimization of chitosan-polyvinylalcohol electrospinning process by response surface methodology (RSM)
Authors: Gholipour A. , Bahrami S. H. , Nouri M. 
Published: August 2014

AbstractResponse Surface Methodology (RSM) is a collection of statistical and mathematical techniques useful for developing, improving, and optimizing processes. RSM was used to model and optimize the electrospinning parameters for the spinning of blend CS/PVA nanofibers. In this study, chitosan (CS)/polyvinyl alcohol (PVA) blend solutions (CS (Mw =1 X 106) in 2% acetic acid and PVA (Mw=12 X 103) in deionized water) with different blend ratio ranging from 10/90 to 50/50 were electrospun. CS/PVA (25/75) blend ratio was chosen as base and optimum ratio due to its suitable morphological properties and diameter. In a constant ratio of blend SEM analysis shows that the diameter of nanofibers changed by varying the voltage and extrusion rate in the electrospinning process. Voltage (10-25 KV) and polymer solutions extrusion rate of (0.2-1 ml/hr) from the nozzle were chosen as variables to control the fiber diameter at similar spinning distances (10 cm). Fiber diameter was correlated to production variables by using a second order polynomial function. The predicted fiber diameters were in good agreement with the experimental results.
Poly(ethylene terephthalate)-carbon nanofiber nano composite for fiber spinning; properties and combustion behavior
Authors: Alongi Jenny , Frache Alberto 
Published: August 2014

AbstractCarbon nanofiber (CNF)-polyethylene terephthalate (PET) blends were previously prepared by melt blending and, subsequently, melt spun in order to obtain nanostructured fibers characterized by high flame retardant properties and resistance to the combustion. The morphological analysis showed that CNFs are homogeneously distributed and finely dispersed within PET matrix. The mechanical properties in tensile testing of the fibers change in the presence of CNFs: the elongation at break increases, whereas the tenacity and the tensile strength decrease. The combustion tests by cone calorimetry reveal a relevant decrease of heat release rate, total heat evolved and total smokes released by the nanocomposites as compared to neat PET.
Urbach tail analysis on the defect states of polypyrrole thin films prepared by AC plasma polymerization Urbach tail analysis on the defect states of polypyrrole thin films prepared by AC plasma polymerization
Authors: John Joseph , Sivaraman Sajeev , Jaylekshmi S. 
Published: August 2014

AbstractPolypyrrole is a widely studied conducting polymer with excellent optical and electrical properties. Polypyrrole thin films in the pristine and iodine doped forms have been prepared by ac plasma polymerization. The in situ doping of iodine during the process of plasma polymerization modified the optical absorption behaviour of the thin films due to the incorporation of charged defects in the film structure. Optical band gap and related constants are estimated from optical absorption studies. The Urbach tail analysis of the pristine and doped thin films shows that more defect levels are created, when the polymerization was carried out in the iodine atmosphere. The electrical properties of these thin films were estimated from the conductivity measurements. It is found that in the case of iodine doped films, the optical band gap decreased and electrical conductivity enhanced when compared to the pristine ones. The results are correlated with the structural differences of the pristine and doped thin films with the help of Fourier Transform Infrared Spectroscopy (FTIR) analysis.
Preparation and properties of fluorosilicone and fluorosilicone elastomer with various contents of trifluoropropyl groups
Authors: Cui Yan , Jiang Wenge , Li Dongmei , Niu Chengqun ,   Jiezhang, Feng Shengyu 
Published: August 2014

AbstractPoly(dimethyl-methyltrifluoropropyl-methylvinyl)siloxanes (PFMVS) with various contents of trifluoropropyl groups were prepared by ring-opening copolymerization of 2,4,6-trimethyl-2,4,6-tris(3,3,3-trifluoropropyl) cyclotrisiloxane (D3F), octamethylcyclotetrasiloxane (D4) and 1,3,5,7-tetramethyl tetravinylcyclotetrasiloxane (D4Vi). All the polymers were characterized by IR, 1HNMR, 29SiNMR, gel permeation chromatography (GPC), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) measurements. The results show that methyltrifluoropropyl-siloxane units in the copolymer can disrupt the molecular regularity and lead to noncrystalline copolymers with low glasstransition temperatures. Moreover, the onset temperatures of thermal degradation and the glass transition temperatures of polymers decrease gradually with the content of trifluoropropyl groups increasing. Then the thermal stability and solvent resistance of elastomers based on PFMVSs were measured. The data of TGA indicate that the thermal stability of fluorosilicone elastomers are less than conventional methyl vinyl silicone rubber (MVQ), but the fluorosilicone elastomers have outstanding solvent resistance. The content of the trifluoropropyl groups influences the performances of elastomer to a certain degree.
Polymer composites as sensing materials for liquid organic solvents – preliminary results
Authors: Frackowiak Stanislaw , Maciejewska Monika , Szczurek Andrzej , Kozlowski Marek 
Published: August 2014

AbstractCarbon black-filled polymer composites were investigated as sensing materials for organic liquids. Polypropylene and polystyrene which were selected as matrices and various amounts of carbon black were considered as the main factors influencing sensitivity of the composites in view of the percolation theory. Disposable filaments were produced of these materials. Change in their electrical resistivity was measured upon immersion in benzene, toluene, xylene, ethylbenzene and their mixtures. It has been found that studied materials were sensitive to the composition of liquid mixtures of organic solvent. Relationships between the filament response and volumetric fraction of the components were presented. The studied materials have shown promising sensing properties, which suggest their applicability for identification and quantification of multicomponent organic liquids.
Synthesis of thermotropic polyurethanes containing ester mesogen units and their mesophase behavior
Authors: Ban Jian-Feng , Lu Shao-Rong , Zhang Chenxi , Liu Ting , Huang Zhiyi 
Published: August 2014

AbstractA series of novel thermotropic liquid crystalline was synthesized from bi(p-hydroxyl benzoic acid)hydroquinone ester (PHQ), triethylene glycol and 2,4- toluenediisocyanate (2,4-TDI) by altering the molar ratio of PHQ and diol, and PHQ was prepared by using hydroquinone and p-hydroxybenzoic acid as raw materials. The thermotropic mesophase behavior, the melting point temperature (Tm) and the isotropization temperature (Ti) of the synthesized polyurethanes were characterized by FT-IR, DSC and POM. It showed that all of the polyurethane polymers exhibited nematic textures at temperature of 110~230 °C. The shift of the melting and isotropization temperature (Tm, Ti) to lower temperature is discussed to be a consequence of the increasing amount of diol content.
Preparation of polyacrylonitrile via AGET ATRP initiated by CCl4
Authors: Ma Jing , Chen Hou , Zong Guangxi , Wang Chunhua , Liu Delong 
Published: August 2014

AbstractA commercially available alkyl halide carbon tetrachloride (CCl4) was used as the initiator for activator generated by electron transfer atom transfer radical polymerization (AGET ATRP) of acrylonitrile (AN) in N,N-dimethyl formamide (DMF). Environmentally benign ascorbic acid (VC) was chosen as the reducing agent and copper bromide (CuBr2) as the catalyst precursor together with iminodiacetic acid (IDA) as the ligand. The polymerization proceeded in a controlled manner as evidenced by kinetic of AGET ATRP of AN, a linear increase of number-average molecular weight (Mn) with monomer conversion and low polydispersity index (PDI) throughout the reactions. The monomer (AN) conversion increased with the increase of VC and CCl4. The value of PDI increased with the increase in concentration of VC. For an increase of CCl4, the value of PDI decreased first and then increased. 1H-NMR spectrum of PAN further confirmed the “living”/controlled feature of AGET ATRP of AN.
Modification and shaping of carbon nanotubes with an electron beam
Authors: Xu Zhiwei , Wang Rui , Wang Chunhong , Liu Liangsen , Chen Lei , Chen Guangwei 
Published: August 2014

AbstractThe paper reviews the modification and shaping of electron beam irradiation on carbon nanotubes (CNTs), as well as how this could be potentially useful for electron beam modification of nanotubes. The influence of irradiation on the mechanical property, electrical property and field effect of CNTs is discussed. Several examples are given with particular emphasis on the cutting, shaping and welding of CNTs by the electron beam in an electron microscope. It is shown that the change of incident electron energy and ambient temperature will lead to the different irradiation results. It is expected that electron irradiation studies will continue to play an important role in the research on CNTs.
Thermal stability, crystallization and mechanical properties of nylon11/montmorillonite nanocomposites
Authors: Li Yingchun , Hu Guosheng , He Bin 
Published: August 2014

AbstractNylon 11 nanocomposites with different montmorillonite loadings were successfully prepared by melt compounding. XRD and TEM show the exfoliated nanocomposites are formed at low montmorillonite concentration (less than 2 wt%) and the intercalated nanocomposites are obtained at higher montmorillonite contents. TGA shows that the thermal stability of the nanocomposites is improved by 27 °C when the montmorillonite content is only 2wt%. At the same time, The crystallization behavior of nylon11/montmorillonite nanocomposites has been studied by means of XRD, DSC.The Avrami equation described well the isothermal crystallization behavior of nylon11 and nylon11/montmorillonite nanocomposites. The results showed that the montmorillonite acted as the nucleating agent and facilitated the crystal growth rate of nylon 11 matrix. The incorporation of montmorillonite did not change the crystal morphology of nylon 11 but increased the crystallization temperature and decreased the crystallization activation energy, which lead to a easy crystallization of nylon11. Mechanical testing shows that the Izod impact strength of all nanocomposites are higher than that of the neat nylon 11, but the tensile strength of the nanocomposites decrease at low nanofiller concentrations (less than 8wt%) and then increased, when the montmorillonite content is 10wt% ,the tensile strength of the nanocomposite is 5% improved than neat nylon 11. This is may be due to the strong interaction between the nylon 11 matrix and the montmorillonite interface.
Tribological behavior of an ultrahigh molecular weight polyethylene in lubricated environments
Authors: Kahyaoglu O. K. , Unal H , Mimaroglu A , Yetgin S.H. 
Published: August 2014

AbstractThe wear and friction performance of GUR 1020 grade ultrahigh molecular weight polyethylene (UHMWPE) polymer was studied in distilled water, HASS (Hank’s balanced salt solution) and several protein lubrication environments. Wear tests were carried out using polymer pin -on AISI 304L stainless steel disc apparatus. Tests conditions were room temperature, 40N, 80N and 120N applied loads and 0.5 m/s sliding speed. For the range of load and speed value of this work, the coefficient of friction and wear rate for UHMWPE polymer decreases with the increase in applied load values. The coefficient of friction is highest and the specific wear rate values is lowest under HASS +HA solution lubricant. The average specific wear rate values for UHMWPE polymer under distilled water and HASS+HA (Hank’s balanced salt solution with Hyaluronic acid) lubrication conditions are in the order of 9x10-15 m2/N and 3x10-15 m2/N respectively. The wear mechanism includes abrasion and adhesive processes.
Copolymerization of acenaphthylene with methacrylic monomers
Authors: Navarro L. , Bilbao E. , Laza J.M. , Vilas J.L. , Garay M.T. , Rodríguez M. , León L.M. 
Published: August 2014

AbstractThe copolymerization of acenaphthylene with methylmethacrylate, ethylmethacrylate, butylmethacrylete, iso-butylmethacrylate and cyclohexylmethacrylate has been carried out in tetrahydrofuran at 323 K and the composition of the copolymers has been determined by size exclusion chromatography using a double RI-UV detector system. Several methods have been applied to obtain the reactivity ratios of the copolymerization process. The glass transition temperature of the copolymers has been obtained by DSC and the thermal stability has been studied by thermogravimetry. Analysis of the degradation volatile products reveals that copolymers degrade mainly by depolymerization.
Hypercrosslinked polystyrene microspheres by suspension and dispersion polymerization
Authors: Šálek Petr , Horák Daniel 
Published: August 2014

AbstractTo determine the influence of particle size on the specific surface area of hypercrosslinked poly(styrene-co-divinylbenzene) (PS) microspheres, two methods were chosen for preparation of particles, suspension and dispersion polymerization. While the former method produced hundred micrometer-sized PS-S microspheres, the latter yielded PS-D particles of ca. 1-μm size. Dispersion copolymerization of styrene (St) and divinylbenzene (DVB) in ethanol was stabilized by (hydroxypropyl)cellulose (HPC) and initiated with dibenzoyl peroxide (BPO). Monodisperse 1.4-μm PS-D microspheres were prepared only in the presence of 3.6 wt% HPC. All microspheres were chloromethylated with chloromethyl methyl ether (CMME), chloromethyl ethyl ether (CMEE) or chloromethyl octyl ether (CMOE) to investigate the effect of the chloromethylation agent on the specific surface area of microspheres. Chloromethylated microspheres were hypercrosslinked in 1,2-dichloroethane (DCE) in the presence of a Lewis acid (SnCl4). The effects of the crosslinker (DVB) and DCE/microsphere ratio on properties of the product were studied. The specific surface area, pore volume and pore size distribution of the microspheres were analyzed by dynamic desorption of nitrogen, cyclohexane regain and mercury porosimetry.
Synthesis, characterization and properties of novel thermally stable copoly(amide-imide)s containing dimethylsilane moieties
Authors: Kolahdoozan Majid , Ghoreishi Monir S. 
Published: August 2014

AbstractNew type of poly(amide-imide)s were prepared based on novel diacid monomer containing softening siloxane groups. Bis(p-aminophenoxy) dimethyl silane (3) was prepared by the reaction of dimethyl dichlorosilane with paminophenol in toluene. N,N'-Bis(4-trimellitimidophenoxy) dimethylsilane (5) as a novel aromatic dicarboxylic acid containing silicone moiety was synthesized by condensation of bis(p-aminophenoxy) dimethylsilane with trimelitic anhydride in acetic acid. The structure of diacid 5 was confirmed using various spectroscopy methods. The direct polycondensation technique was used for the polyamidation of monomer 5 with several aromatic diamines using pyridine / 2-methylpyrrolidone / triphenyl phosphite / CaCl2 as condensing agent. The resulting novel poly(amideimide- siloxane)s were obtained in high yields and inherent viscosities. These polymers were characterized using FT-IR, 1H-NMR, thermogravimetric and elemental analysis techniques. The results show that silicone modified poly(amideimide) s show high solubility and excellent thermal stability.
A predictive model for the synthesis of polylactide from lactic acid by response surface methodology
Authors: Agarwal P. , Mondal A. , Mishra P.K. , Srivastava P. 
Published: August 2014

AbstractThe present work describes the statistical process optimization of a lowcost production process of PLA using organometallic (stannous octoate) compounds. The process optimization for both lactide and polylactide, was developed by factorial design and response surface methodology. The influence of different experimental parameters such as reaction temperature, time, concentration of catalyst and co-initiator concentration on the yield of lactide and polylactide has been evaluated. There are many studies reported on the synthesis of polylactide but no earlier study exists for the application of statistical analysis in determining the interactions among the process variables for lactide and polylactide production. Central composite experimental design with multiple linear regression has been used to estimate the coefficients of the polynomial model equation for the yield(s) of both lactide and polylactide. The statistical significance of polynomial model equation was validated by F test (ANOVA). Determination coefficient (R2) values found to be 0.913 and 0.958 for lactide and polylactide respectively, states that predicted values were in good agreement with the experimental values. Results of the statistical analysis showed that the model fits in all cases. Above synthesised polymer was characterized by FT-IR, 1H-NMR, DSC and GPC to confirm the polymer structure and properties.
Preparation and characterization of poly(acryl amide-coacrylic acid)/nay and Clinoptilolite nanocomposites with improved methylene blue dye removal behavior from aqueous solution
Authors: Zendehdel M. , Barati A. , Alikhani H. 
Published: August 2014

AbstractThe nanocomposites of poly(acryl amide-co-acrylic acid) with NaY and Clinoptilolite were prepared using ammonium persulfate as an initiator and N,N′- methylene bis acryl amide as the cross-linker. The morphology was characterized by SEM and the structure of nanocomposite materials was studied with XRD and FT-IR that showed the interaction between porous materials and poly(AAm-co- AAc). Thermo gravimetric analyzer (TGA) curve shows that all the chain-extended poly(AAm-co-AAc) are stable up to 250 °C and maximum weight loss occurs at 890 °C. The TGA results indicated higher stability for poly(acryl amide-co-acrylic acid)/NaY and Clinoptilolite composites than poly(AAm-co-AAc). The adsorption and desorption behavior of methylene blue were investigated for nanocomposites. It was shown that poly(AAm-co-AAc)/NaY and Clinoptilolite nanocomposites have higher adsorption than NaY, Clinoptilolite and poly(AAm-co-AAc) alone. This effect was attributed to good interaction between the hydroxyl group in porous materials and carboxylic group in poly(AAm-co-AAc) with methylene blue.