bluuebunny/crossref_metadata_2025 huggingface dataset:
Separation of linear and star-shaped polystyrenes by two-dimensional chromatography
Authors: Gerber Johannes , Radke Wolfgang
Published: August 2014

Investigation of star-shaped polystyrenes using gradient chromatography shows a retention that only depends on the total molecular weight and not on the number or molecular weight of the arms. In contrast, size-exclusion chromatography (SEC) separates according to hydrodynamic volume. For a mixture of a star polymers having an arm molecular weight of 4800 and a linear polystyrene a direct 2-dimensional separation using gradient chromatography as a first dimension and SEC as a second dimension resulted in a clear separation of the different topologies. Star polymers of higher arm molecular weight could not be separated from their linear analogues by direct coupling of gradient chromatography and SEC.
Degradation of polymeric systems aimed at temporary therapeutic applications: Structure-related complications
Authors: Vert Michel
Published: August 2014

The number of degradable or biodegradable polymers that are aimed or claimed as aimed at therapeutic purposes is rapidly increasing in literature. In most cases, contributions deal primarily with synthesis. However it is the matching of degradation characteristics to application requirements that is important. This contribution, based on personal experience, is aimed at discussing some of the structure-related complications that can be expected when a polymeric therapeutic device degrades in an aqueous medium or in an animal organism. It is shown that dramatic changes can be observed because of selective degradation of some parts leading to the formation of undesired degradation by-products or undesired changes of properties.
Thermodynamic and electrochemical study of multicomponent polymer complexes of varying composition
Authors: Sharma nee Chhabra Mamta , Sharma Sandeep
Published: August 2014

Multicomponent complexes of varying composition have been prepared from poly(methacrylic acid-co-acrylamide), poly(ethyleneimine) and poly(vinylpyrrolidone). Stability constants and related thermodynamic parameters have been determined. Interpretations have been sought in terms of secondary binding forces and their magnitude.
Carbon-chain polymers ‘grafting from’ inorganic nanoparticles
Authors: Liu Peng
Published: August 2014

‘Grafting from’ methods can achieve higher percentages of grafting than ‘grafting to’ methods in the preparation of carbon-chain polymer grafted inorganic nanoparticles (CCP-INs). ‘Grafting from’ methods - such as one-pot method, macro-monomer, macro chain transfer agent, macro-initiator, and macro-iniferter methods, used for the preparation of CCP-INs in our laboratory in the recent years - are reviewed and the grafting parameters are compared. Characterization of the CCP-INs is also described.
Antimicrobial activity of polystyrene particles coated by photo-crosslinked block copolymers containing a biocidal polymethacrylate block
Authors: Lenoir Sandrine , Pagnoulle Christophe , Detrembleur Christophe , Galleni Moreno , Jérôme Robert
Published: August 2014

A commercially available poly(ethylene-co-butylene) copolymer, endcapped by a short polyisoprene block and a hydroxyl group (PI-b-PEB-OH), has been derivatized into a macroinitiator for atom transfer radical polymerization (ATRP) by esterification of the hydroxyl end-group by an activated bromidecontaining acyl bromide. Two types of triblock copolymers, PI-b-PEB-b-poly- (dimethylaminoethyl methacrylate) (PDMAEMA) and PI-b-PEB-b-poly[2-(tert-butylamino) ethyl methacrylate] (PTBAEMA), have been synthesized and used to coat polystyrene particles. These coatings have been permanently immobilized by UV cross-linking of the isoprene units. They exhibit a biocidal activity against Gramnegative bacteria either intrinsically in case of the PTBAEMA block or upon quaternization of the PDMAEMA block by octyl bromide. The antimicrobial activity is directly related to the concentration of coated PS particles in the medium.
Curing behaviour of epoxy resins with a diamine bearing an azobenzene group
Authors: Schab-Balcerzak Ewa , Bednarski Henryk , Janeczek Henryk , Sęk Danuta
Published: August 2014

Abstract N,N-Diglycidylaniline (DGA) has been cured with the new chromophore 2,4-diamino-4'-methylazobenzene (DMAB). The curing kinetics of this aminophenyl epoxy resin/DMAB system was studied in isothermal experiments by means of differential scanning calorimetry. Autocatalytic behaviour is seen in the first stage of the cure and can be described by a model proposed by Kamal. The later stage is practically diffusion-controlled (beyond the glass transition). The diffusion effect is introduced into Kamal’s equation. Parameters such as rate constants and activation energies are calculated. Good agreement between calculations and experimental data is found. The curing kinetics of bifunctional DGA is compared with that of trifunctional N,N-diglycidyl-4-glycidyloxyaniline (DGOA) with the same tetrafunctional curing agent DMAB. The rate constants for DGA + DMBA are slightly higher than those for the DGOA + DMAB system. The activation energy for the former (E1 = 64.1 kJ/mol, E2 = 56.2 kJ/mol) is lower than for the latter system (E1 = 71.6 kJ/mol, E2 = 70.5 kJ/mol). DGA needs to be cured at a lower temperature than DGOA. The relationships between glass transition temperature, Tg, and rate of conversion and time of curing is discussed as well. DGA cured with DMAB exhibits a lower Tg (220°C) and thermal stability than DGOA + DMAB (Tg = 240°C) because of the lower functionality of the DGA resin. Preliminary investigations of optical grating recording in the new material were carried out. The presence of azobenzene groups in such epoxy systems enables their application as potential materials for holography.
Kinetics and mechanism of miniemulsion polymerization of a sparingly water-soluble fluoro monomer
Authors: Suzuki Kiyoshi , Yamada Yasutaka , Fujita Kazumi , Nomura Mamoru , Saito Hideya
Published: August 2014

In order to clarify the kinetics and mechanism of miniemulsion polymerization of a sparingly water-soluble monomer, the miniemulsion polymerization of 1,1,2,2-tetrahydroperfluorodecyl acrylate was conducted at 50°C using potassium persulfate as initiator and sodium dodecyl sulfate as emulsifier, respectively. It was found that the rate of polymerization was proportional to the 0.65 power of the initial initiator concentration and to the 0.30 power of the number of miniemulsion droplets (latex particles). It is pointed out that the kinetics of this polymerization system may be subject to the modified case III kinetics of emulsion polymerization with predominant bimolecular termination in the aqueous phase.
Monitoring morphology and properties of hybrid organicinorganic materials from in situ polymerization of tetraethoxysilane in polyimide polymer: 1. Effect of the coupling agent on the microstructure and interfacial interaction
Authors: Kaddami Hamid , Becker-Willinger Carsten , Schmid Helmut
Published: August 2014

Transmission electron microscopy (TEM), small angle X-ray (SAXS) and dynamical mechanical thermal analysis (DMTA) were used to characterize the morphology and thermo-mechanical properties of hybrid organic inorganic materials. These materials were based on polyimide (PI) and tetraethoxysilane (TEOS). Polyimide polymer is prepared from 4,4’-oxydianiline (ODA) 2,2-Bis(3- amino-4-hydroxyphenyl) hexafluoro-propane (6F-OHDA) pyromellitic dianhydride (PMDA) polyamic polymer. In one family of hybrid materials 3- isocyanatopropyltriethoxysilane (ICTS) is used as coupling agent in order to enhance the interfacial interaction between polyimide and silica. It was possible to modulate the morphology as well as the optical and thermo-mechanical properties of these hybrid materials depending on the formulation used. TEM and SAXS analysis indicated that silica domains on the nanoscale level are obtained when coupling agent is used in the formulation. Additionally the TEM and SAXS analysis indicated that miscibility of the organic and the inorganic phases on the molecular scale is obtained in the hybrid films when ICTS as coupling agent is added to the polyamic acid. These techniques show a fractal structure of the hybrid materials with coupling agent. This was confirmed with DMTA analysis which shows very high temperature relaxation (more than 450°C). From this result it could be derived that the addition of ICTS causes a morphological transformation from discrete particulate microstructure to fine interpenetrated or co-continuous phases. The intimate miscibility of the phases is accompanied at the same time by the amelioration of thermo-mechanical properties of the hybrid films.
Homopolymerization of a highly polar zwitterionic methacrylate in ionic liquids and its copolymerization with a non-polar methacrylate
Authors: Strehmel Veronika , Laschewsky André , Wetzel Hendrik
Published: August 2014

Free radical homo- and copolymerization of the highly polar 3-(N-[2- methacryloyloxyethyl]-N,N-dimethylammonio)propane sulfonate with the nonpolar n-butylmethacrylate was investigated in the ionic liquids 1-butyl-3-methyl imidazolium tetrafluoroborate and 1-butyl-3-methylimidazolium hexafluoro phosphate, and compared to analogous polymerizations in standard solvents. Higher molar masses are obtained for the zwitterionic homopolymer when the polymerization is carried out in an ionic liquid compared to the classical reaction in water. Although homopolymerization of the sulfobetain monomer as well as of nbutylmethacrylate results in phase separation during the polymerization process, copolymerization of a stoichiometric ratio of the two monomers in the ionic liquids produced transparent gels indicating that no macrophase separation occurs. The use of ionic liquids as reaction medium improved the copolymerization behavior of the two methacrylates significantly. Whereas only minor amounts of n-butyl methacrylate were incorporated in the copolymer when synthesized in acetonitrile, the content of the non-polar monomer units in the zwitterionic copolymer approached increasingly its content in the polymerization mixture when ionic liquids were employed as solvents.
Activation of organoclays and preparation of polyethylene nanocomposites
Authors: Chaiko David J.
Published: August 2014

A dimethyl dihydrogenated tallow ammonium bentonite, edge modified with 1-hydroxydodecane-1,1-diphosphonic acid, was activated by intercalation of polyethylene-block-poly(ethylene glycol). A high-density polyethylene (HDPE) nanocomposite was produced by the gradual dilution of the intercalated organoclay with HDPE, via melt mixing, until a final clay concentration of 0.3 wt% was reached. While polymer crystallinity was unaffected by the addition of the clay, polymer transparency increased dramatically. Microscopic examination of compression molded films verified that polymer nucleation increased to such an extent that the normal spherulitic structure was completely absent. A significant reduction in gas transmission accompanied the increased film clarity. Compared to the pure polymer, oxygen and water vapor permeabilities were reduced by approximately 55 and 70%, respectively. With proper dispersion, significant improvements in both physical and barrier properties are achievable by the incorporation of nanoclays into polyolefins. Additionally, it is significant that these benefits can be realized at clay concentrations consistent with those of common polymer additives, like stabilizers, clarifiers, and colorants.
Characterization and photoinduced properties of photo chromic polymers. 1. Polyesterimides with 4-amino 4´-nitro azobenzene moieties
Authors: Schab-Balcerzak Ewa , Sapich Beate , Stumpe Joachim , Sobolewska Anna , Miniewicz Andrzej
Published: August 2014

Novel photochromic polyesterimides (PEIs) with two different types of azobenzene units as side groups have been synthesized from 2,2’-{4-[(4- nitrophenyl)-azo} phenyl]iminobis(ethyl benzene-1,2-dicarboxylic acid anhydride-4- carboxylate) and diamines: 2,4-diamino-4’-methylazobenzene and 2,4-diamino-4’- (trifluoromethoxy)azobenzene. An analogous polyesterimide with one azobenzene group based on 1,3-phenylendiamine has been prepared to compare with these PEIs. Molecular structural characterization for these polymers has been achieved by FTIR, 1H NMR and UV-Vis spectroscopy. These amorphous polyesterimides are thermally stable up to 260°C as follows from the thermogravimetric analysis (TGA). The glass transition temperatures (Tg) for the resulting polyimides have been determined from DSC thermograms and are in the range of 141-210°C. The irradiation with linearly polarized light of an Ar+ laser results in the induction of optical anisotropy within the initially isotropic films. Light induced optical anisotropy in polymer films has been studied by examining the value of generated dichroism using Ar+ laser (λ = 488 nm) and by holographic polarization grating recording performed at λ = 514.5 nm. The value of photoinduced dichroism is in the range of 0.15-0.26. The induction of dichroism and kinetics of grating inscription have been investigated in relation to the presence of the second type of azobenzene group in the polymer and its substitution.
The Attenuated Total Reflection Infrared Analysis of Surface Crystallinity of Polyhydroxyalkanoates
Authors: Hong Shinn-Gwo , Chen Wei-Ming
Published: August 2014

The surface crystallization of three different polyhydroxy alkanoates (PHAs), poly(3-hydroxybutyrate) (PHB), PHB-co-5 weight percent 3-hydroxyvalerate (PHBV5), and PHB-co-12 weight percent 3- hydroxyvalerate (PHBV12), under different processing conditions is analyzed with depth profiling attenuated total reflection spectroscopy (ATR) and differential scanning calorimetry (DSC). The results of ATR indicate that there is a crystallinity distribution on the outer 2 microns thick surface layer. The degree of crystallinity in different penetration depths follows the order of 0.92μ > 0.41μ > 1.70μ for all three hot-pressed PHAs studied and the outer surfaces have a much greater crystallinity than the bulk. The surface crystallinity of specimens is in the order of PHB > PHBV5 > PHBV12 regardless of the different penetration depths analyzed which is consistent with the DSC results. It is also obtained that the effect of annealing in enhancing the crystallization of PHAs is more significant in the surface layer. The surface crystallinity of PHAs obtained after annealing follows the trend of Petri-dish side of solvent-cast PHB > hotpress PHB > air side of solvent-cast PHB > PHBV5 > PHBV12. The difference in crystallinity between the surface and the bulk of PHAs decreases with the addition of 3-hydroxyvalerate but increases after annealing. It is confirmed that the film forming method and the substrate contacted affect the surface crystalline state of PHAs which is attributed to the changes in crystallization conditions in the surface materials.
Highly Stereospecific Polymerizations of 1,3-Butadiene with Cobalt(II) Pyridyl Bis(imine) Complexes
Authors: Kim Jae Sung , Ha Chang-Sik , Kim Il
Published: August 2014

A series of prototypical Co(II)-based pyridyl bis(imine) complexes {[2- (ArN=C(Me))2C5H3N]CoCl2} (Ar = 2,6-C6H3Me2, 2,5-C6H3Me2, 2,4-C6H3Me2, 2,3- C6H3Me2) bearing two methyl substituents on each imine aryl group are studied as precatalysts for the homopolymerization of 1,3-butadiene. They showed very high polymerization activities associated with ethylaluminum sesquichloride (EAS) as a cocatalyst. The Co(II) catalysts containing less hindered pyridyl bis(imine) ligands, say [2-(2,3-C6H3Me2N=C(Me))2C5H3N]CoCl2 complex, showed highest activity to give high molecular weight polymers. All catalysts yielded cis-1,4-polybutadienes up to 96.4% with cis-1,4 regular structure.
Luminescent polyvinylpyrrolidone/ZnO hybrid nanofibers membrane prepared by electrospinning
Authors: Lu Xiaofeng , Zhang Wanjin , Zhao Qidong , Wang Lifeng , Wang Ce
Published: August 2014

Polyvinylpyrrolidone (PVP)/ZnO composite nanofibers were successfully prepared by a facile method called electrospinning technique. The synthetic strategy involved two steps: (1) Preparation of ZnO sol in ethanol solution. PVP molecules then added into the above sol and achieved the appropriate rheology for electrospinning; (2) Electrospun the above solution to obtain fibers of PVP/ZnO composites. Scanning electron microscopic (SEM) analysis of the composite nanofibers revealed network structures like a spider’s web. Transmission electron microscopy (TEM) showed small nanoparticles of the ZnO component with an average particle size in the range of 3 - 4 nm and a good dispersion. X-Ray diffraction results showed that a pure wurtzite phase was obtained in PVP fibers. XPS spectra proved that the Zn and O elements existed in PVP/ZnO composite nanofibers. FTIR and UV-vis spectroscopy were used to characterize the structure of PVP/ZnO composite nanofibers. The photoluminescence properties of the PVP/ZnO composite nanofibers were also investigated.
Mesomorphic Phase Behavior in Comb-like Polymer- Surfactant Complex
Authors: Akiba Isamu , Masunaga Hiroyasu , Murata Shouichi , Sasaki Kanako
Published: August 2014

It was found that a comb-like complex consisting of poly[2-(N,Ndimethylamino) ethyl acrylate] (PDAEA) and p-dodecylbenzene sulfonic acid (DBSA) formed mesomorphically ordered lamellar phase at room temperature where PDAEA and DBSA are in molten state. The lamellar phase shows optical anisotropy, although the individual components are always isotropic. In addition it is found that the optical anisotropy of the PDAEA-DBSA complex completely disappears with accompanying order-disorder transition of the lamellar morphology with elevating temperature.
Fluorescence Study of Fılm Formatıon From Hard/ Soft Latex Blends
Authors: Uğur Şaziye , Holl Yves
Published: August 2014

The effects of blend composition on film formation is studied using the SSF and UV-visible (UVV) techniques. Latex blend films were prepared from mixtures of two types of particles in dispersion, one composed of a high-Tg (hard) pyrene (P) labeled polystyrene (PS) latex; the other a low-Tg (soft) poly(n-butyl acrylate) (BuA1). Twelve different blend films were prepared in various hard/soft latex compositions at room temperature and annealed at elevated temperatures above glass transition temperature (Tg) of polystyerene for 10 min. Fluorescence intensity (IP) from P was measured after each annealing step to monitor the stages of film formation. The evolution of transparency of latex films was monitored using photon transmission intensity, Itr. Film morphologies were examined by atomic force microscopy (AFM). The results showed that as the amount of hard component in the blend is decreased, a significant change occured in both IP and Itr curves at a certain critical weight fraction (50%wt) of PS hard latex. Above this fraction two distinct film formation stages, which are named as void closure and interdiffusion were seen in fluorescence data. However, below 50%wt PS no film formation stages were observed. Below this fraction, Itr data showed that phase separation process occurs between PS and BuA1 polymers. These results were also confirmed by AFM pictures. Film formation stages for 50-100%wt range of PS were modeled and related activation energies were calculated. There was no observable change in activation energies confirming that film formation behavior is not affected by varying the blend composition.
Synthesis of cationic flocculants based on acrylamide and [2-(acryloyloxy)ethyl]trimethylammonium chloride copolymers by semicontinuous inverse microemulsion polymerization. Part II: influence of initiator addition conditions, initial temperature, pH and comonomer concentration on flocculating performance
Authors: Sasia Pedro M. , Ochoa G. José R. , Río Francisca , Díaz de Apodaca Elena , Nieto Javier , Torrecilla Jesús , Katime Issa , Escudero Francisco J.
Published: August 2014

The influence of initiator concentration, specific flow rate of initiator addition (Qsp), initial copolymerization temperature (Ti), aqueous phase pH and total comonomer concentration (TCC) on flocculating performance of latex particles of acrylamide and [2- (acryloyloxy)ethyl]trimethylammonium chloride copolymers with a cationic charge density of 40%, obtained by inverse microemulsion copolymerization by using a surfactant blend of Arlacel 83 and Softanol 90 as emulsifier and Rolling M-245, a mixture of n-decane and n-tetradecane in about 40/60 weight ratio, as oil phase, has been studied for high TCC, ranging from 28 to 34.5% (w/w). Comonomer inverse microemulsion copolymerizations were carried out in the semicontinuous mode by adding continuously an aqueous solution of sodium metabisulfite as initiator into stirred inverse comonomer microemulsions. Initiator concentration has a strong influence on viscosity, viscometric structuring degree (VSI) and average weight molar mass (Mw) of copolymers in the range from 5 to 25 g/L. Both viscosity and Mw decrease with increasing initiator concentration. Best flocculating performance is obtained from 10 to 20 g/L, values at which VSI shows a minimum. Under the experimental conditions used, Qsp (153 to 310 mL/h/kg of comonomer), Ti (25 to 35ºC) and aqueous phase pH (2.5 to 4.5) have almost no influence on both viscosity and VSI and, hence, on flocculating performance. On the contrary, TCC has a slight influence on copolymer viscosity but a strong one on VSI which increases dramatically with TCC, being the worst flocculating performance obtained at the highest TCC studied (34.5% (w/w)). Flocculating performance results are explained in terms of copolymer structuring degree and collapsed state of copolymer chains inside latex particles as well as in terms of the composition drift with conversion.
Composition distribution of poly(propylene-g-styrene) synthesized by solid-state grafting of styrene onto spherical polypropylene reactor granules
Authors: Deng Qing-tian , Fu Zhi-sheng , Zhang Le-tian , Xun Jun-ting , Fan Zhi-qiang
Published: August 2014

An iPP-g-St graft copolymer synthesized by free-radical initiated solidstate grafting polymerization of styrene in nascent spherical iPP granules was effectively fractionated by temperature gradient extraction fractionation (TGEF) into fractions of different styrene content. The fractions were characterized by FTIR, 1H-NMR, DSC, PLM and WAXD. The fraction extracted at room temperature (25 0C) is homopolymer of styrene, and the fractions collected at 70, 90, and 105 0C are iPP-g-St graft copolymer with decreasing degree of grafting. All the fractions of the grafting product contain a certain amount of styrene, meaning that almost all the iPP chains in the granules are accessible to the grafting monomer. The internal morphology of the iPP granules is highly porous, which enables the grafting monomer and the radicals to reach at each iPP chain during the polymerization. As styrene content of the iPP-g-St fraction increases, its crystallinity decreases, the size of iPP lamella decreases, and the crystalline morphology becomes more irregular.
Effect of degree of substitution on the mechanical and thermomechanical properties of lauroyl cellulose ester films
Authors: Joly Nicolas , Martin Patrick , Liénard Luc , Rutot Delphine , Stassin Fabrice , Granet Robert , Krausz Pierre , Cavrot Jean-Paul
Published: August 2014

Cellulose-based plastic films were prepared in homogeneous media with a range of lauroyl fatty acid attachments by ester formation, expressed as the degree of substitution (DS). The esters were cast to form films and their mechanical properties studied. This study showed a surprising relationship between DS and elastic modulus as well as DS and tensile strength, where a peak was observed at DS 2.4. The unexpected variation of static elastic modulus (E) was confirmed by dynamic mechanical analysis (DMA) and this trend was also observed for glass transition temperature (Tg). These results are discussed in relation to sample cohesion.
Poly(styrene/α-tertbutoxy-ω-vinylbenzyl-polyglycidol) micro spheres for the preparation of novel photonic crystals
Authors: Basinska Teresa , Kergoat Loïg , Mangeney Claire , Chehimi Mohamed M. , Slomkowski Stanislaw
Published: August 2014

We report on the preparation of a novel photonic crystal assembled from poly(styrene/α-tertbutoxy-ω-vinylbenzyl-polyglycidol) microspheres. The latex particles were fully characterized in terms of size (271 nm, Dw/Dn=1.004), electrophoretic mobility (-3.79x10-8 m2V-1s-1) and surface chemical composition (evidence for a PGL-rich particle surface). They were then assembled into 3D colloidal crystal showing an optical stop band in the visible region. The λmax for the Bragg diffraction peak is 570 nm. As the particles under study are highly hydrophilic and biocompatible, this work opens up new opportunities for the design of photonic crystal-based biosensing devices.
Synthesis and cellular uptake of superparamagnetic dextran-nanoparticles with porphyrinic motifs grafted by esterification
Authors: Lucas Romain , Granet Robert , Sol Vincent , Le Morvan Caroline , Policar Clotilde , Rivière Eric , Krausz Pierre
Published: August 2014

This paper describes new superparamagnetic nanoparticles bearing dextran-grafted porphyrins with effective cellular uptake properties. They average 110 nm in diameter and are composed of a 5 nm iron oxide core coated with protoporphyrin-grafted dextrans. These particles show good magnetic properties, are avidly incorporated into cultured cancer cell lines, and thus present a great potential for cellular imaging and photodynamic therapy applications.
Self-Assembly of Methacrylic Nanostructured Copolymers Containing Polyhedral Oligomeric Silsesquioxanes
Authors: Molina D. , Levi M. , Turri S. , Penso M.
Published: August 2014

Two hybrid copolymer series obtained by free-radical copolymerization of methacrylcyclohexyl Polyhedral oligomeric silsesquioxane (POSS) with butyl methacrylate or 2-ethylhexylmethacrylate were characterized by 1H-NMR spectroscopy, gel permeation chromatography (GPC), X-rays Diffraction (XRD), differential scanning calorimetry (DSC) and thermo-gravimetric analysis (TGA). Reactivity ratios were calculated by low yield composition data suggesting the formation of random copolymers with low probability of poly-POSS sequences. XRD studies showed the crystallization behaviour of the inorganic phase independently on the POSS content; however sample processing by solvent casting effectively hindered the copolymer self-assembling ability. DSC suggests the formation of polyphasic structures with Tg increasing with POSS content, and with endothermal peaks occurring at higher temperature. Finally TGA shows an improved thermal stability of hybrid copolymers with char yield correlated to the level of inorganic phase.
Non-isothermal crystallization kinetics of Poly(phenylene sulfide)/hyperbrtanched Poly(phenylene sulfide) blends
Authors: Yan Bo , Chen Yanmo , Zhu Meifang , Liu Ting
Published: August 2014

The non-isothermal crystallization behaviour of poly(phenylene sulfide) (PPS) in blends with hyperbranched poly(phenylene sulfide) (HPPS) was studied by means of differential scanning calorimetry (DSC). It was observed that the PPS crystallization temperature was found to decrease upon addition of the HPPS. It suggested that the crystallizability was reduced. The Ozawa equation was valid not only for neat PPS, but also for the blends. A notable reduction in Avrami exponents for the PPS/HPPS blend systems suggested that the nucleated process leads to rodshaped growth with thermal nucleation. The cooling crystallization function, which represents the rate of non-isothermal crystallization, was found to decrease with increase in HPPS content. The Ea value increases with the increase in HPPS content. Our results indicated that crystallization of the PPS was hampered by content of hyperbranched poly(phenylene sulfide).
Infinite dilution diffusion coefficients of organic solvents in nascent polyethylene particles by inverse gas chromatography measurements
Authors: Yan Xiaowei , Wang Jingdai , Shan Yibin , Yang Yongrong , He Chao
Published: August 2014

Diffusion coefficients of four organic solvents: dichloromethane, trichloromethane, tetrachloromethane and n-hexane in polyethylene particles at infinite dilution were determined by use of inverse gas chromatography (IGC). The polymer particles were used as supplied by the producer to pack the chromatographic columns. This allowed a direct measurement of the interested properties in a particle with the same morphology obtained at the reactor outlet. The particle morphology was investigated and classical mathematical model for chromatographic process was adopted based upon the analysis of particle microstructure. It was found that the limitation step for mass transfer was in the polymer matrix rather than in macropores, and when interpreted in terms of diffusion coefficients for spherical particles, the measured diffusion coefficients compared favourably with predicted values from literature relationships and free volume theory.
Synthesis and characterization of methoxy poly(ethylene glycol)-b-poly(DL-lactide-co-glycolide-co-ε-caprolactone) di block copolymers: Effects of block lengths and compositions
Authors: Baimark Yodthong , Srisa-ard Mangkorn , Threeprom Jirasak , Molloy Robert , Punyodom Winita
Published: August 2014

Methoxy poly(ethylene glycol)-b-poly(D,L-lactide-co-glycolide-co-ε- caprolactone) diblock copolymers, designated as MPEG-b-PDLLGCL, with different MPEG block lengths and DLL:G:CL ratios were synthesized via ring-opening polymerization in bulk using MPEG and stannous octoate as the initiating system. The diblock copolymers were characterized using a combination of FT-IR, 1HNMR, GPC and DSC. The percentage yields of the diblock copolymers were in excess of 90%. 1H-NMR analysis confirmed that the PDLLGCL blocks contained at least some random character. From their DSC curves, the diblock copolymers were amorphous in morphology. Their glass transition temperatures decreased as the MPEG block length increased and as G and CL units were incorporated.
Synthesis and bharacterization of poly(vinyl alcohol)-boric acid beads from PVA with several hydrolysis degrees
Authors: Melo Adriana de , Borges Daniel L. G. , Debacher Nito A. , Curtius Adilson J.
Published: August 2014

This work describes the synthesis and characterization of poly(vinyl alcohol)-boric acid (PVA-BA) sphere-like beads. The PVA-BA beads were prepared by the dropwise addition of PVA aqueous solutions to a boric acid solution under constant stirring and controlled temperature. Different temperatures for bead formation as well as PVA with several hydrolysis degrees were used and tested. PVA with several hydrolysis degrees were characterized regarding molecular mass and intrinsic viscosity, while characterization of PVA-BA beads was carried out using thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). The results obtained with TGA have shown that structural changes occurs in PVA following the reaction with boric acid and that the spheres formed are thermally stable, whereas SEM analysis demonstrated that symmetric sphere-like beads were formed, with considerable porosity, which are requisite for solid supports when applied to effluent treatment. Trace element extraction tests were carried out using inductively coupled plasma mass spectrometry (ICP-MS). Without the addition of a chelating agent, no significant extraction occurred from acidic solutions, while after the addition of ethylenediaminetetracetate, less than 10% of the trace element content was extracted from the aqueous phase by the PVA-BA beads. However, after the addition of ammonium O,O-diethyldithiophosphate (DDTP), over 10% of As, Co, Cr, Fe, Sr and Zn, 40% of Cd and 70% of Pb were extracted from acidic solutions, even without any further optimization. The results have shown that the synthesized PVA-BA beads are potential alternatives for trace element extraction in effluent treatment.
Study of the effect on conductivity and its uniform distribution in injection molded composite polymer bipolar plate
Authors: Shia-Chung Chen , Ming-Yi Shih , Yi-Chang Lin
Published: August 2014

In this study, PPS blended with as high as 50 wt% carbon fiber were injection molded. Effects of molding conditions as well as the melt flow condition parallel and perpendicular to fluid channel on the surface conductivity was investigated. It was found that mold temperature affects the surface conductivity of molded parts significantly. Using a variable mold temperature control system based on electromagnetic induction heating, the conductivity of the molded part increase by about 152% when the peak mold temperature increases from 120 °C to 210 °C. The channel layout also helps the fiber to orient more randomly leading to an increase in the conductivity. The channel design parallel to melt flow increases the conductivity by 152% and when it is perpendicular to melt flow, the conductivity increases by 95%. Channel layout perpendicular to melt flow direction provides more influence on the fiber reorientation than that of the parallel design.
Flexible Fluid Pump Using Magnetic Composite Gels
Authors: Mitsumata Tetsu , Horikoshi Yuki , Takimoto Jun-Ichi
Published: August 2014

A flexible fluid pump made of magnetic composite gels has been developed. The magnetic composite gel was sodium alginate or poly(vinyl alcohol) gel in which barium ferrite particles were dispersed. The pump consisted of a magnetic gel-rotor and a driving magnet. The rotor demonstrated the rotational motion in response to a rotational magnetic field generated by the driving magnet. The gel-rotor had the shape of a screw so as to deliver water efficiently. The diameter of the rotor was varied from 3.8 to 5.5 mm and the diameter of the tube for delivering water was kept as 6 mm. Flow rates pumped by the rotor increased with increasing the diameter, length, and rotation speeds of the rotor. The maximum flow rate of 34 ml/min was achieved when the rotation speeds was 5000 rpm. The rotor with a diameter of 300 μm was also successfully synthesized, however the rotor did not deliver water in a microtube with a diameter of 500 μm. Processing of the gel-rotor, and the efficiency of the water delivery are presented.
Simple Derivation of the First Cumulant for the Rouse Chain
Authors: Lisy Vladimir , Brutovsky Branislav , Tothova Jana
Published: August 2014

A simple analytic expression for the first cumulant of the dynamic structure factor of a polymer coil in the Rouse model is derived. The obtained formula is exact within the usual assumption of the continuum distribution of beads along the chain. It reflects the contributions to the scattering of light or neutrons from both the internal motion of the polymer and its diffusion, and is valid in the whole region of the wave-vector change at the scattering.
Stability and particle size of polypyrrole dispersion using sodium dodecylbenzenesulfonate as surfactant
Authors: Xing Shuangxi , Zhao Guoku
Published: August 2014

Polypyrrole (PPy) dispersion was prepared using FeCl3·6H2O as oxidant in the presence of sodium dodecylbenzenesulfonate (SDBS) as surfactant. The formation of the micelles and the electrostatic interaction between PPy and SDBS were considered the driving forces for the formation and stability of the dispersion. UV/Vis/NIR, FTIR spectra and SEM images were studied to confirm the structure and morphology of the PPy dispersion, respectively. Polymerization of pyrrole under different preparation conditions including the concentration of the surfactant, the pyrrole monomer and the oxidant and also the addition of acid were carried out in order to investigate their effects on the stability and average particle size of the dispersions. The conductivity of the resulting PPy particles was measured and a comparison between the PPy and polyaniline dispersion formed with SDBS as surfactant was also given.
Fracture toughness of controlled-rheology polypropylenes
Authors: Salazar Alicia , Rodríguez Susana , Navarro José Manuel , Ureña Alejandro , Rodríguez Jesús
Published: August 2014

The rheological, thermal, tensile and fracture properties of controlledrheology polypropylene processed via organic peroxides have been evaluated. Different concentrations of di-tert-butylperoxide (DTBP) were used in this work. Both melt flow index and the crystallinity index increased slightly with the peroxide content while the melting temperature tend to decrease. This was attributed to the decrease in the molecular weight which mainly affects the amorphous region, especially the entanglement density of this semycrystalline polymer. As a consequence, the tensile stress and strain at break reduced as the peroxide content increased. The elastic-plastic response of the different polypropylenes at room temperature promotes the use of J-integral to determine the fracture toughness. A multiple specimens method was utilized. The crack initiation resistance and the crack propagation resistance were influenced by the molecular weight, decreasing as the peroxide content increased. The micromechanisms of failure were analyzed via scanning electron microscopy.
Electrical performance and stability of polypyrrole coated PET fibres
Authors: Varesano Alessio , Ferrer Anna Ibarzabal , Tonin Claudio
Published: August 2014

PET non-wovens were treated with intrinsically electro-conducting polypyrrole (PPy) produced by chemical oxidative in situ polymerization from pyrrole aqueous solution, using Fe3+ or S2O82- as oxidant, and different dopants. The resulting materials have different electrical performances and thermal properties depending on the thickness of the PPy coating, the amount and the type of dopant embedded into the polymer layer, the type of oxidant used and the pH of the polymerization bath. Samples were maintained at different temperatures and humidity with the aim of gathering information about the electrical performance stability in different environmental conditions. Generally, PPy shows conductivity decay when maintained at high temperature, whereas the conductivity slightly decreases when stored for a long time at cold or room temperature. Moreover, the PPy coating enhances the resistance to heat of the PET fibres (i.e. increase in melting temperature).
Effects of chemical structure and plasma treatment on the surface properties of polysulfones
Authors: Ioan Silvia , Filimon Anca , Avram Ecaterina , Ioanid Ghiocel
Published: August 2014

The correlation between surface tension parameters and the chemical composition of polysulfone, chloromethylated polysulfone and quaternized polysulfone membranes, before and after plasma treatment, was investigated. Calculations are based on the geometric mean approach of Owens, Wendt, Rabel and Kälble, as well as on the theoretical methods involving quantitative structureproperty relationships on the basis of the group contribution techniques. The chemical modifications of polysulfone membranes and the low pressure plasma treatment affect the contact angle corresponding to different liquids. Consequently, the total surface tension and the polar component increase with the substitution degree of chloromethylated polysulfone and with the quaternization degree of the ammonium groups, in quaternized polysulfone samples. The plasma treatment modifies the surface energy of the samples, increasing their surface polarity and wettability. Surface wettability trends were also studied by means of the free energy of hydration between compounds and water.
Rheological properties of grafted maleic anhydride based polypropylene composites filled with organoclay and glass fibers
Authors: Lee Seung Hwan , Youn Jae Ryoun
Published: August 2014

Exfoliated polypropylene/layered silicate nanocomposites and chopped glass fiber reinforced composites were prepared by a melt compounding process using maleic anhydride modified polypropylene (PP-g-MAH). The effect of fillers on morphological and rheological properties in melt mixing of polypropylene matrix with compatibilizer was investigated and compared with various measurements. It was observed that polypropylene/layered silicate nanocomposites exhibited remarkable reinforcement compared with the conventional composites filled with glass fibers which were dispersed at micrometer scale. The nanocomposites had larger storage modulus at low frequency region and outstanding strain hardening behavior than those of pure polypropylene or glass fiber reinforced composites. It was shown that glass fiber reinforced composites had lower elastic properties and steady state elongational viscosities than pure polypropylene melt. Contrary to glass fiber reinforced composites, it was confirmed that 3-dimensional network structure due to strong intermolecular bonding between polypropylene matrix and layered silicates affected particular rheological properties of nanocomposites.
Synthesis, Characterization, and Performance Evaluation of Polymeric Hindered Amine Light Stabilizers (HALS) in EPDM
Authors: Rana Sravendra , Singh Raj Pal
Published: August 2014

Polymeric hindered amine light stabilizer (HALS), wherein the hindered amine functionality was attached to the brominated ethylene-propylene-diene terpolymer (EPDM) was synthesized. The brominated EPDM was synthesized as an intermediate for the synthesis of a new polymeric hindered amine light stabilizer. The grafting and functionalization reactions were characterized by FTIR and 1HNMR spectroscopy. The photostabilizing efficiency of this polymeric HALS was studied and compared with conventional HALS under accelerated weathering conditions. The results of the study give evidence for superiority of polymeric HALS over that of melt blended conventional HALS.
Residual Stress and Rheological Behavior of Polymeric Nanocomposites
Authors: Song Young Seok
Published: August 2014

Rheological and mechanical characterizations were carried out for carbon nanotubes/poly(ethylene oxide) (PEO) nanocomposites to examine the effect of surface modification of carbon nanotubes on the CNT dispersion state. Residual stress in the gap-wise direction of the nanocomposites was measured using the layer removal method. It was found that the different chemical treatments for CNT surface make a big difference in the dispersion state of the CNTs and that the nanocomposites filled with better dispersed CNTs possess higher storage and elastic moduli. From the rheological observations, rheological percolation structure was found to exist in the nanocomposites, which was confirmed by morphological experiments. The residual stress data showed that stronger residual stress is developed in the PEO nanocomposites by non-isothermal cooling than in pure PEO.
Thermal Stability and Aging Characteristics of HNBR/Clay Nanocomposites in Air, Water and Oil at Elevated Temperature
Authors: Anmin Huang , Xiaoping Wang , Demin Jia , Yanmei Li
Published: August 2014

Hydrogenated nitrile rubber (HNBR)/clay nanocomposites are prepared using conventional two-roll mill mixing technique. The structure and morphology of nanocomposites are characterized using wide angle X-ray diffraction (WAXD) and transmission electron microscopy (TEM). Both intercalated and exfoliated clay structures are observed in HNBR/clay nanocomposites. The thermal stability of the nanocomposites is studied using thermogravimetric analysis (TGA) and TGA-Fourier transform infrared (FTIR) spectroscopy. The effect of organoclay on physical and mechanical properties of HNBR vulcanizates before and after aging in air, water and oil at 178 °C is also investigated. It is found that adding organoclay in HNBR elastomer greatly improves material thermal stability and aging performance in different medium at elevated temperature.
Storage Modulus of Poly(vinyl alcohol) Gels Loaded with Polyelectrolyte Particles
Authors: Mitsumata Tetsu , Nagata Mitsuaki , Taniguchi Takashi , Kawaguchi Seigou
Published: August 2014

We have investigated the viscoelastic properties of poly(vinyl alcohol) (PVA) gels loaded with a polyelectrolyte particle of poly(styrene-co-sodium styrene sulfonate) to find the effect of electric charges on the storage modulus of the gel. The storage modulus decreased with increasing volume fraction of particles, and it was independent of the strain, indicating linear viscoelasticity. The viscoelastic properties of PVA gels containing non-charged particles of aluminium hydroxides were also studied. While the degree of swelling kept a constant value, the storage modulus largely increased with the volume fraction. PVA gels containing noncharged particles underwent a large nonlinear viscoelastic response suggesting the particles connect each other in the gel. Viscoelastic properties of the PVA gel loaded with charged and non-charged particles have also been discussed.
Synthesis and characterization of thermosensitive hydrogels with both supramolecular and hyperbranched structures
Authors: Ping Zhang , Qunfeng Liu , Yanxun Lan , Jianbo Shi , Mangeng Lu
Published: August 2014

New novel kinds of thermosensitive hydrogels with supramolecular structures were synthesized by reversible addition fragmentation chain transfer (RAFT) polymerization of N-isopropylacrylamide (NIPAM) and polypseudo rotaxanes in the presence of N,N- methylenebisacylamide (BIS) as a cross-linker. The polypseudorotaxanes were prepared by supramolecular self-assemblies of α- cyclodextrins threaded onto (4A-PEG) polymers. The structure of the hydrogels were characterized in detail with FTIR techniques. The analytical results demonstrated that a channel-type crystalline structure of inclusion complexes (ICs) remains in as-obtained hydrogels. Their swelling behavior was measured gravimetrically in the temperature range from 20 to 60 °C. The supramolecular structured hydrogels by RAFT polymerization (RAFT gels) showed accelerated shrinking kinetics to conventional hydrogel (CG), surprisingly.
Concrete + polyester + CaCO3: Mechanics and morphology after gamma irradiation
Authors: Martínez-Barrera Gonzalo , Espinosa-Pesqueira Manuel Eduardo , Brostow Witold
Published: August 2014

We have studied effects of gamma radiation on mechanical performance of polymer concrete (PC) containing varying concentrations of an unsaturated polyester resin and calcium carbonate. The compressive strength values increase from the zero dose (non-irradiated PC) to 10 kGy; afterwards we find a periodical change as a function of the resin concentration. The highest compressive strength corresponds to the highest resin concentration but the changes are not too large. Compressive strain values also go symbiotically with the resin concentration. All our composites - including irradiated and non-irradiated - have higher strength values than those reported for earlier polyester + concrete materials. The compressive modulus values follow the same pattern as the compressive strength and strain.