bluuebunny/crossref_metadata_2025 huggingface dataset:
In vivo wear of polyethylene glenoid components in total shoulder arthroplasty
Authors: Swieszkowski Wojciech , Frankle Mark , Bersee Harald E. N. , Kurzydlowski Krzysztof J.
Published: August 2014

Loosening of the glenoid component after a total shoulder arthroplasty, leading to pain and the need for a revision operation, accounts for one third of all shoulder replacement complications. It has been shown that glenoid loosening could be a result of osteolysis of periprosthetic bone induced by polymeric wear debris. The aim of this study was to determine the amount and pattern of in vivo wear of polyethylene glenoid components by examining a set of so-called retrievals. Six glenoid components were retrieved and examined (5 all-polyethylene and 1 metal-backed). The average time of functioning of these components in human bodies was 10 years with the shortest time of 7 and longest 14 years. Four components were scanned using a laser scanner. The results of measurements have been used to generate geometrical models of the retrievals using CAD software. These models have been subsequently used to determine the maximum depth and volumetric wear rate for each component. All six retrievals were examined using scanning electron microscopy (SEM). The maximum volumetric wear rate and wear depth for the analyzed retrievals was 30 mm3/year and 0.2 mm/year, respectively. From SEM analysis of the retrievals it was found that at macroscopic level the worn surfaces consist of (a) polished and (b) scratched regions. Intensive wear areas and fine multidirectional scratches were dominant in all retrievals. Random scratches were also observed, most probably due to third body wear (cement particles). In two implants pitting areas and surface micro-cracks have been observed, which most likely result from subsurface fatigue.
Radical crosslinking during polyhydrosilylation between fluorinated and silicone molecules: a model study
Authors: Longuet Claire , Ratsimihety Amédée , Guida-Pietrasanta Francine , Ganachaud François , Boutevin Bernard
Published: August 2014

The present study deals with an explanation for crosslinking reactions that occur during the polyhydrosilylation of telechelic Si-H silicones with divinylperfluoro molecules. For a better understanding of the chemical process, a model reaction was performed and characterized by a full battery of techniques, including the different nuclei NMR analyses. Even if hydrosilylation occurs, side methyl groups on the silicon atoms also react with tert-butoxy radicals. Abstraction of a hydrogen radical from the methyl side group of the silicone chains allows the vinyl fluorinated molecules to add on polydimethylsiloxane and to bridge chains together.
Synthesis, characterization and ring-closing depolymerization of furanic polyesters
Authors: Kamoun Wided , Salhi Slim , Abid Souhir , Tessier Martine , Gharbi Rachid El , Fradet Alain
Published: August 2014

Furanic polyesters were prepared by the bulk polycondensation of 5,5'- isopropylidene-bis(2-furoic acid) with 1,2-ethanediol, 1,4-propanediol and 1,6- hexanediol, and were characterized by size exclusion chromatography, NMR and MALDI-TOF MS. The ring-closing depolymerization of these polyesters was then investigated at 10 g/L concentration in 1-methylnaphthalene at 130 - 240°C. Chain flexibility, the use of zinc diacetate catalyst and, particularly, the presence of hydroxy end-groups were found to be favourable factors for the formation of high yields of cyclic oligoesters. A side reaction leading to the formation of non-reactive furyl-terminated species took place when the reactions were carried out at high temperature (240°C), limiting the yield of cyclic oligoesters.
Rheological characterization of polymer-based nanocomposites with different nanoscale dispersions
Authors: Seong Dong Gi , Kang Tae Jin , Youn Jae Ryoun
Published: August 2014

Polyamide 6 - clay nanocomposites with different nanoscale dispersions were prepared by melt compounding via twin-screw extrusion and their internal structures were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The rheological behaviour of these nanocomposites in shear and extensional flow were investigated using an Advanced Rheometric Expansion System and an Elongational Melts Rheometer in connection with the analysis by XRD and TEM. Nanocomposites with fully exfoliated structure and with poorly dispersed structure showed very different rheological behaviour. In general, addition of clay increased the viscosity and the storage modulus of nanocomposites, but different rheological behaviours were observed depending upon the degree of clay dispersion in the polymer matrix. In shear flow, only the exfoliated nanocomposite showed solid-like plateau behaviour in storage modulus and strong shear-thinning behaviour in shear viscosity. In extensional flow, only fully exfoliated nanocomposites showed strain-hardening behaviour, which is caused by the interaction between nanoparticles as well as between polymer molecules and nanoparticles.
Comparison of two algorithms for calculation of the apparent rate constant in the kinetic modelling of diallyl terephthalate bulk polymerization
Authors: Hace Iztok
Published: August 2014

In the present study a comparison was made of two most frequently used algorithms for calculation of the apparent rate constant in the kinetic modelling of bulk cross-linking diallyl terephthalate (DAT) polymerization with four different peroxide initiators, bis(4-tert-butylcyclohexyl) peroxydicarbonate, dicyclohexyl peroxydicarbonate, benzoyl peroxide and dicumyl peroxide, in the temperature range from 50 to 150°C and at three different initiator loadings. The first algorithm is the CCS algorithm developed by Chiu, Carratt and Soong and the second is the S algorithm developed by Smoluchowski. Only two kinetic parameters had to be found by fitting a previously proposed kinetic model for bulk DAT polymerization, developed by Hace et al., to measured conversion points. Conversions and other necessary physico-chemical properties used for kinetic modelling were obtained from our previous kinetic studies on DAT polymerization.
High-throughput screening of the chemical composition distribution of random styrene-butyl acrylate copolymers
Authors: Romero Iván García , Pasch Harald
Published: August 2014

The development of high-throughput liquid chromatographic techniques for the analysis of styrene-butyl acrylate (SBA) copolymers is discussed. The analysis time in size-exclusion chromatography (SEC) can be reduced to about 3 min per sample when high-throughput SEC columns and high flow rates are used. In gradient HPLC, small columns with improved separation efficiencies can be applied. The time requirements can be decreased to less than 2 min per sample. Using the high-throughput HPLC technique, the chemical composition distribution of high-conversion SBA copolymers can be analyzed in a fast and efficient way. The calibration of HPLC separation is conducted by coupling the HPLC system with FTIR through the LC-transform interface. A comparison of the chemical compositions of the copolymers obtained by 1H NMR, off-line FTIR and coupled HPLCFTIR verifies the accuracy of the high-throughput copolymer analysis approach.
Influence of adding poly(vinyl alcohol) fibres to poly(methyl methacrylate) matrix on the fracture behaviour of fibrereinforced composites
Authors: Pavelka Vladimir , Jancar Josef , Nezbedova Eva
Published: August 2014

This paper reports on the relationship between structure and mechanical properties of poly(methyl methacrylate) (PMMA) reinforced with randomly oriented short poly(vinyl alcohol) (PVA) fibres. Special focus was on the effect of fibre content on the impact resistance of PMMA/PVA composites. Instrumented Charpy impact tests were carried out to characterize the impact resistance of PMMA/PVA composites. Linear elastics fracture mechanics was used to determine the dynamic critical strain energy release rate (GId) and the critical stress intensity factor (KId). Fracture surfaces were observed using scanning electron microscopy (SEM). Dynamic mechanical analysis was carried out to describe the viscoelastic response of the material. Finally, the behaviour of PMMA/PVA composites was interpreted using current short-fibre composite models. It was shown that a small amount of added PVA fibres (0.42 - 1.68 vol.-%) led to an increase of elastic modulus and yield stress under impact conditions. GId was also slightly increased, but KId remained unchanged. Good agreement was found between SEM observations and fracture toughness measured under impact loading.
Three-dimensional numerical simulation of viscoelastic flow through an abrupt contraction geometry
Authors: Kwon Young Il , Seo Dongjin , Youn Jae Ryoun
Published: August 2014

A numerical scheme for simulating three-dimensional viscoelastic flow was developed. The three-dimensional finite volume method (FVM) based on a non-staggered grid and the semi-implicit method for pressure-linked equations (SIMPLE) were adopted to solve the continuity and momentum equations. As we used a non-staggered grid, the momentum interpolation method (MIM) was employed to avoid checkerboard type pressure fields. Viscoelastic properties of the fluid were described by the Phan-Thien and Tanner (PTT) model, which was treated by the compressive interface capturing scheme for arbitrary meshes (CICSAM). The elastic viscous split stress scheme (EVSS) was used to decouple the velocity and the stress fields. Algebraic equations obtained by the above schemes were handled by an iterative solver and a multi-grid method was applied to accelerate convergence. In order to verify the scheme developed in this study, Newtonian flow in a rectangular duct was studied and the resulting velocity fields were compared with the analytical flow fields. Then viscoelastic flow in 4:1 contraction geometry, one of the most frequently used benchmarking problems, was predicted by applying the fully three-dimensional finite volume method.
Structure and thermodynamic modelling of Pluronic L64 solutions
Authors: Ghaouar Naoufel , Aschi Adel , Jebari Mohamed Mondher , Gharbi Abedelhafidh
Published: August 2014

The aim of the present work is to model structure and thermodynamic properties of Pluronic L64 solutions (triblock copolymer with hydrophilic ends and a hydrophobic middle). We first determined the micelle size by dynamic light scattering at various temperatures. This helps to understand the particle formation mechanism in solution and the interparticle interactions by following the virial coefficient as well as its temperature dependence. Two semi-empirical intermolecular potentials were tested to predict sample properties. First, we used a pure Lennard- Jones pair potential and then we introduced the Lu and Marlow (LM) contribution in its repulsive part. All quantities of interest were computed using the integral equation scheme with hybridized mean spherical approximation. We found that the LM contribution corrects structure and thermodynamic properties of the system by taking into account the effect of particle size.
COPOINT – a simple computer program to determine copolymerization parameters by numerical integration
Authors: Beginn Uwe
Published: August 2014

A computer program is introduced that evaluates the parameters of binary copolymerizations from comonomer/copolymer composition data as obtained from polymerization experiments with finite monomer conversion. The program numerically integrates a given copolymerization equation in its differential form and can be applied to a broad variety of functions. Copolymerization parameters are obtained by minimizing the sum of square differences between measured and calculated polymer compositions with respect to the copolymerization parameters. Errors of the fitted parameters are estimated from the statistical error of the sum of square differences, as well as from a quadratic approximation of this sum in the vicinity of the optimized values of the copolymerization parameters.
Surface functionalization by smart binary polymer brushes to tune physico-chemical characteristics at biointerfaces
Authors: Uhlmann Petra , Houbenov Nikolay , Minko Sergiy , Stamm Manfred
Published: August 2014

Polymer brushes consist of an assembly of polymer chains that are attached by one end to the surface with sufficient grafting density. Binary brushes constituted from two incompatible polymers can be used in the form of ultrathin polymeric layers as a versatile tool for surface engineering to tune physicochemical surface characteristics as wettability, surface charge, chemical composition or morphology, and furthermore to create responsive surface properties. It is also possible to fix surface structures obtained in this way by (photo)crosslinking of the layers. Mixed brushes of oppositely charged polyelectrolytes are representing a special case of responding surfaces, which are sensitive to changes of the pH in aqueous environment. It is shown that structural changes occur in the plateau region of the adsorption isotherm of a model protein and that changes of the pH also cause changes in the structure of the adsorbed protein layer.
Bis(vinylcyclopropane) and bis(methacrylate) monomers with cholesteryl group for dental composites
Authors: Choi SooWhan , Hessamian Anahita , Tabatabai Monir , Fischer Urs Karl , Moszner Norbert , Ritter Helmut
Published: August 2014

Novel bis(vinylcyclopropane)-based monomers with cholesteryl group and high molecular weight were prepared. The phase behaviour of the synthesized monomers was investigated. The obtained macromonomers showed a polymerisation shrinkage that was significantly lower compared to dimethacrylates used in dental composites.
Synthesis and characterization of 4- and 6-arm star-shaped poly(ε-caprolactone)s
Authors: Meier Michael A. R. , Schubert Ulrich S.
Published: August 2014

Star-shaped poly(ε-caprolactone) (PCL) polymers were synthesized and fully characterized by gel permeation chromatography, matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS) as well as 1H NMR spectroscopy. First a series of four-armed PCLs with different molecular weights was prepared and analyzed with the mentioned analytical techniques revealing that the applied ring-opening polymerization was controlled and defined star-shaped polymers could be synthesized. Subsequently, also the synthesis of six-armed PCL polymers was investigated with the conclusion that also these starshaped polymers could be prepared in a controlled fashion.
Characterisation of ‘wet’ polymer surfaces for tissue engineering applications: Are flat surfaces a suitable model for complex structures?
Authors: Safinia Laleh , Blaker Jonny J. , Maquet Véronique , Boccaccini Aldo R. , Mantalaris Athanassios , Bismarck Alexander
Published: August 2014

Tissue engineering scaffolds are 3D constructs that simulate the growth environment in vivo. The present work aims to address the question of whether thin films, i.e., flat surfaces, are a suitable model for more complex 3D structures? With this in mind a complete study of the morphology and surface chemistry of poly(D,Llactide) (PDLLA) substrates, fabricated into two different structures, is presented. The polymer structures studied include a 3D, porous, foam-like scaffold prepared by the thermally induced phase separation (TIPS) method and flat polymer thin films made by solvent casting. Based on the maximum bubble point test, a new method to assess the wettability of wet pore wall surfaces inside highly porous 3D structures was developed and tested. The maximum pore diameter determined using the maximum bubble point test for the total wetting liquids was confirmed through image analysis of scanning electron micrographs. The method allows the determination of the contact angle between the wet pore wall and a contacting liquid. The captive bubble method was employed to characterise the wettability of flat polymer films in contact with water. Both structures were further characterised using zeta- (ζ-) potential measurements to assess the surface chemistry of the polymer. The results demonstrate that PDLLA contains acidic functional groups and is hydrophobic. In order to evaluate the sensitivity of the test methods, the polymer surfaces were modified by protein adsorption using fibronectin and collagen. ζ-Potential and wettability measurements show that proteins indeed adsorb on virgin PDLLA surfaces. Protein adsorption causes the wettability of the PDLLA for water to improve. Our results strongly indicate that flat surfaces are not a suitable model for surfaces in complex 3D structures such as highly porous tissue engineering scaffolds. Such scaffolds must be characterised as a 3D system.
Preparation and release behavior of pH and ionic sensitive chitosan/poly(vinylpyrrolidone) semi-IPN beads for coenzyme A
Authors: Guo Baolin , Yuan Jinfang , Gao Qingyu
Published: August 2014

A series of pH- and ionic sensitive semi-interpenetrating polymer network (semi-IPN) beads of chitosan (CS) and poly(vinyl pyrrolidone) (PVP) were prepared using glutaraldehyde as crosslinking agent and characterized for the release of coenzyme A (Co A). The swelling behavior of the semi-IPN beads and the influential factors, such as the component ratio of CS and PVP, the loaded amount of Co A, the pH and ionic strength of the release medium on Co A release were studied. The results showed that within 48 h the cumulative release rate of Co A decreased with Co A loading content, ionic strength increase or crosslinking time increase; when the weight ratios of CS to PVP in the drug-loaded beads were 100:0, 80:20, 60:40, 50:50, 40:60 and 20:80, the cumulative release rates of Co A at pH 2.1 solution were 95.2, 72.1, 73.2, 74.2, 86.5 and 80.1%, respectively, and they were 22.7, 30.1, 28.0, 33.1, 38.4 and 35.2% at pH 7.4 solution, respectively. All the results indicated that the CS/PVP semi-IPN beads were suitable for drug delivery systems.
Characterization of polydimethylsiloxane rubber upon photochemical, thermal, salt-fog ageings and exposure to acid vapours
Authors: Delor-Jestin F. , Tomer N. S. , Singh R.P. , Lacoste J.
Published: August 2014

The changes in the chemical structure and the physical properties of a filled crosslinked polydimethylsiloxane rubber were monitored as a function of various ageing factors. The variables included photochemical, thermal, salt-fog ageings and exposure to acid vapours. Unaged and aged samples were studied by IR spectroscopy, hardness measurements, Differential Scanning Calorimetry (DSC) and thermogravimetric analysis (TGA) coupled with IR spectroscopy. No significant oxidation was detected after all ageings, except for nitric acid treatment. The presence of aluminium trihydrate was clearly identified as responsible for the observed chemical changes. Then an important vulnerability of this filled silicone rubber towards the cross-linking reactions provoked by usual ageings was also detected. The DSC-thermoporosimetry measurements of the mesh size distribution gave a comparison of cross-linking densities for each ageing. The complementary analysis with TGAIR allowed us to differenciate the thermal stability of the formulation after various ageings and to acquire new knowledge about thermal decomposition.
Polyketone Nanocomposites by Palladium-Catalyzed Ethylene-Carbon Monoxide-(Propene) Co(Ter)polymerization Inside an Unmodified Layered Silicate
Authors: Miller Hamish A. , Moneti Simonetta , Vizza Francesco , Passaglia Elisa , Bianchini Claudio , Bronco Simona , Ceriegi Silvia , Sulcis Roberta , Frediani Marco , Ciardelli Francesco , Costa Giovanna
Published: August 2014

Composites from Na-montmorillonite with a content in inorganic material ranging from 3 to 98 wt % were prepared in situ either by copolymerization of ethylene and CO or by terpolymerization of ethylene, propene and CO using a palladium(II) catalyst modified with 1,3-bis(diphenylphosphino)propane. This catalytic system is active in polar media and allowed to produce nanocomposites starting from unmodified Na-montmorillonite in water-methanol solutions. The morphological analysis, performed on samples with less than 40 wt % silicate by XRD and TEM, showed the formation of either intercalated or exfoliated (nanocomposite) structures, depending on the initial amount of the layered silicate in the reactor as well as the presence of propene as comonomer. Improved thermal stability of the hybrid materials, as compared to the corresponding organic polymers, was shown by TGA. A preliminary study of the blending of some polyketone nanocomposites with polyamide (nylon-6) was carried out by melt mixing at high temperature in a Brabender mixer.
Synthesis of cationic flocculants based on acrylamide and [2-(acryloyloxy)ethyl]trimethylammonium chloride co polymers by semicontinuous inverse microemulsion co polymerization. Part I: Criteria for selection of comonomer formulation
Authors: Ochoa G. José R. , Río Francisca , Sasia Pedro M. , Katime Issa A. , Escudero Francisco Javier , Díaz de Apodaca Elena , Mestre Javier Nieto
Published: August 2014

The influence of surfactant blend composition, organic solvent (oil) structure and cationic charge density (CCD) on stability of comonomer inverse microemulsions of acrylamide and [2-(acryloyloxy)ethyl]trimethylammonium chloride has been studied in order to obtain criteria for selecting comonomer inverse microemulsions before copolymerization resulting in copolymer inverse microemulsion useful as flocculants. Results show that optimum HLB can be explained by cohesive energy ratio theory and it increases with CCD; the higher the hydrophobic chain length of surfactants in surfactant blend, the lower the minimum surfactant blend concentrations (SBCm) needed to obtain stable inverse microemulsions; and linear organic solvents allow a decrease of the SBCm required for stabilizing comonomer inverse microemulsions.
Removal of Pentachlorophenol from Water Using Novel Smart Hydrogel Microspheres
Authors: Szczubiałka Krzysztof , Karewicz Anna , Moczek Łukasz , Zomerska Karolina , Nowakowska Maria
Published: August 2014

The thermoresponsive hydrogel microspheres were obtained by copolymerization of N-isopropylacrylamide (NIPAM) and 2-hydroxyethyl methacrylate (HEMA) crosslinked with N,N’-methylenebisacrylamide (BIS). The hydrogel was then functionalized using 1-naphthyl glycidyl ether (NGE) to attach naphthyl chromophores, which absorb UV light and act as photosensitizers. The ability of the functionalized microspheres to photosensitize dechlorination reactions was confirmed using pentachlorophenol (PCP) as a model compound.
Synthesis and characterization of glycosylated nano particles
Authors: Lepoittevin Bénédicte , Masson Sébastien , Huc Vincent , Haut Christian , Roger Philippe
Published: August 2014

Functionalized polymer nanoparticles have been synthesized by emulsifier-free emulsion polymerization of styrene with amino-functionalized monomers. Two monomers were used: the well-known 2- aminoethylmethacrylate and a new monomer with a styrenic polymerizable function, 4-(2-aminoethylthio)methylstyrene. The latexes were characterized by gravimetry, dynamic light scattering and colorimetric titration in order to obtain the styrene conversion, the hydrodynamic diameter, the particle size distribution and the concentration of surface amino groups, respectively. Then, glycosydic molecules such as maltose, lactose, maltotriose and galactopyranosylethanal were covalently grafted to the nanoparticles by amidation or reductive amination.
Impact Modification of Polyoxymethylene (POM)
Authors: Uthaman Nalini , Majeed Abdul ,   Pandurangan
Published: August 2014

Polyoxymethylene (POM) was blended with various weight percentages of ethylene propylene diene terpolymer (EPDM) and ethylene vinyl acetate copolymer (EVA) separately in a twin screw extruder under optimum conditions. The mechanical properties of the blends such as tensile strength, impact strength and % elongation were measured. Increasing content of EPDM and EVA up to 7.5% increases the impact strength of POM. Addition of elastomer beyond 7.5% decreases the impact strength due to the poor adhesion between plastic and elastomer phase. POM/EPDM blends compatibilised with EVA showed improved impact strength. The present study reveals that the impact strength of POM can be improved by blending with EPDM and EVA. The incorporation of EVA as compatibiliser into POM/EPDM causes significant improvement in impact strength. Scanning electron microscopy (SEM) reveals enhanced adhesion of POM and EPDM in the presence of EVA up to the extent 5 parts per hundred of resin (phr) resulting in improved dispersion of the elastomer in the plastic matrix.
Studies on the Odd-Even Effect of Methylene Spacers in Bismaleimides
Authors: Feng J. L. , Yue C. Y. , Chian K. S.
Published: August 2014

The synthesis of a series of bismaleimides based on diamines containing flexible units of variable length is presented. These structures were characterized by FTIR and NMR. The changes in spectra are dominated by the CH2 stretching and deformation vibrational bands. The wavenumber of methylene provides a sensitive measure for the chain packing geometry. An attempt has been made to explain the odd-even effects at the molecular level on the basis of the article results. DSC was used to monitor the thermal properties of the samples. The melting points of the bismaleamic acids and bismaleimides are affected by odd-even effect. The reactivity of maleimide group was analyzed. Positions of signals in FTIR and NMR spectra show that BMI should be more stable as the chain length increase.
Synthesis and evaluation of pH-sensitive glycopolymers for oral drug delivery systems
Authors: Mahkam Mehrdad , Mohammadi Reihaneh , Ranaei Siadat Seyed Omid , Ranaei-siadat Seyed Ehsan
Published: August 2014

Sucrose esters (SE) are surfactants with potential pharmaceutical applications because of their low toxicity, biocompatibility, and excellent biodegradability. Biodegradable and biocompatible copolymeric hydrogels based on glucose-6-acrylate-1, 2, 3, 4-tetraacetate (GATA) and methacrylic acid (MAA) were designed and synthesized. Because of the growing importance of sugar-based hydrogels as drug delivery systems, these new pH-responsive glucose-containing copolymeric hydrogels were investigated for oral drug delivery. The GATA monomer was synthesized and characterized. The copolymeric hydrogel was synthesized by free-radical polymerization. Azobisisobutyronitrile (AIBN) was the free-radical initiator employed and Cubane-1, 4-dicarboxylic acid (CDA) linked to two 2-hydroxyethyl methacrylate (HEMA) group was the crosslinking agent (CA) used for hydrogel preparations. The hydrogels were characterized by differential scanning calorimetry and FT-IR. Equilibrium swelling studies were carried out in enzyme-free simulated gastric and intestinal fluids (SGF and SIF, respectively). A model drug, olsalazine [3, 3-َazobis (6-hydroxy benzoic acid)] (OSZ) an azo derivative of 5-aminosalicylic acid (5-ASA), was entrapped in these gels and the in vitro release profiles were established separately in both enzyme-free SGF and SIF. The drug release was found to be faster in SIF. The drug-release profiles indicated that amount of drug release depends on their degree of swelling and crosslinking.
Synthesis and Characterization of the Bismaleimides Containing Aliphatic-ether Chain for Microelectronics Application
Authors: Feng J. L. , Yue C. Y. , Chian K. S.
Published: August 2014

This project aims to develop and characterize a series of bismaleimide (BMI) polymers based on maleic anhydride and aliphatic-ether diamines. The effects of varying the chain length of aliphatic-ether diamines on the resultant bismaleimide systems were evaluated so that their suitability for microelectronics applications could be evaluated. The synthetic reaction and properties of the bismaleimide materials were investigated using Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), Thermo- Gravimetric Analysis (TGA), Dielectric Thermal Analysis (DEA) and rheometry. Results showed that thermal, dielectric and rheological properties were all affected by the main chain length of BMI. The magnitude of the dielectric constant at 100 kHz increases with the increasing chain length. The curing peak temperature, curing heat and degradation temperature of BMI, all decrease with the increasing chain length.
The influence of 4,4’-bis(6-hydroxyhexoxy)biphenyl moieties on properties of polyurethanes based on 4,4’-methylenebis(cyclohexyl isocyanate)
Authors: Łazarewicz Tymon , Haponiuk Józef T. , Balas Adolf
Published: August 2014

Two series of polyurethanes (PUs) were synthesized from a low molecular weight diol - 4,4’-bis(6-hydroxyhexoxy)biphenyl (BH6), a high molecular weight diol - poly(1,6-hexylene adipate)diol (PHA) and 4,4’-methylenebis (cyclohexyl isocyanate) (HMDI) using two fractions of different trans,trans isomer content (uT), respectively: 16%, 46%. The effect of low molecular diol content (uB) in the total mass of the diols used for synthesis on properties of PUs was investigated by DSC, DTA, TGA, polarization microscopy, WAXS, DMTA and tensile testing. For segmented PUs microphase separation is observed and melting temperatures of hard segment (HS) microphases are almost constant within the series for uB≥ 40%. The growth of hard segment content (uHS) induces rectilinear growth of crystallization enthalpy of HS microphases. PUs of uT= 46% show birefringence of HS microphases at uBB ≥ 40%. Glass transition temperatures of HS microphases shift towards lower values with a decrease of uB. PUs of u B = 80 and 100% are stiff, for 20 - 60% elastomeric properties are observed, and in absence of low molecular diol moieties (uB= 0%) plastic behaviour is shown when stretched. Phase inversion is observed between u B BB = 60 and 80%. Thermal stability of PUs (by TGA and DTA) does not depend on uBand uT.
Synthesis of highly sulfonated polystyrene-based block copolymers soluble in tetrahydrofuran
Authors: Janata Miroslav , Kůdela Vlastimil , Gromadzki Daniel , Štěpánek Petr , Nallet Frédéric , Diat Olivier , Vlček Petr , Toman Luděk
Published: August 2014

Polystyrene-block-polyisoprene with hydrogenated polyisoprene block (Shellvis 50) was sulfonated to a high degree (up to 42 mol% of styrene units) using acetyl sulfate as sulfonation agent in various chlorinated solvents. Membranes were prepared from the tetrahydrofuran solution of the sulfonated copolymer by casting. The membranes were characterized by conductivity and SAXS measurements.
A Novel Approach For Synthesizing Composite Polymer Electrolytes with a Stereocomplex Poly(methyl meth acrylate) for electrochromic devices
Authors: Ahmad Shahzada , Ahmad Sharif , Agnihotry S.A.
Published: August 2014

A novel approach has been adopted for synthesizing composite polymer electrolytes with a blend of atactic poly(methyl methacrylate) (a-PMMA) and isotactic PMMA (i-PMMA) owing to their ability to form stereocomplex structures, especially double helix like structures. Nanocomposite polymeric electrolytes based on gel polymeric electrolyte (GPE) consisting of stereocomplex PMMA, propylene carbonate (PC) and LiClO4 has been synthesized. For the stabilization of polymer electrolytes and for good processability, fumed silica nanoparticles have been added in different proportions up to 6 wt% to GPE resulting in composite polymeric electrolytes (CPEs). Thermally stable, low volatile CPEs without the cost on electrochemical stability can thus be obtained, being promising candidates as polymeric electrolytes in many electrochemical devices in general, and in particular electrochromic windows.
Functionalization of poly(vinyl alcohol) by addition of methacryloyl groups: characterization by FTIR and NMR and optimization of reaction conditions by RSM
Authors: Crispim Edson G. , Piai Juliana F. , Schüquel Ivânia T. A. , Rubira Adley F. , Muniz Edvani C.
Published: August 2014

The modification of poly(vinyl alcohol) (PVA) with glycidyl methacrylate (GMA) in DMSO catalyzed by TEMED is reported in this paper. PVA was dissolved in DMSO and reacted with GMA at 30 ºC in a closed vessel under N2 gas bubbling for 24 hours. The reaction was characterized by FTIR and NMR (1H, 13C/DEPT and HETCOR) spectroscopies. The reaction occurs by transesterification through the insertion of methacryloyl groups into PVA chains and probably with the formation of glycidol as a by-product. The degree of substitution (DS) that represents the number of methacryloyl groups inserted was determined through 1H NMR spectra based on the ratio between the averaged area due to the vinyl hydrogen from methacryloyl groups at δ̣ 5.6 ppm and δ 6.0 ppm and the total area of the vinyl hydrogen and hydroxyl hydrogen of PVA. By use of response surface methodology the experimental conditions were optimized. The optimum conditions were 62 ºC with a reaction time of 6 hours. In these optimized conditions, the reactions using the molar ratios [-OH(PVA)/GMA] equal to 1/0.10, 1/0.25, 1/0.50, 1/0.75 and 1/1 were investigated. The response surface was based on the model DS= −19.70 + 6.09x10−1T +1.93 t − 3.89x10−3 T2 − 5.21x10−2t2 − 2.14x10−2 T * t, where T is the temperature (°C) and t the reaction time (hours). This model explained 99.20 % of the 99.64 % explainable statistical data. Using the optimized conditions, it is possible to produce a desired modified PVA, (or PVA-Ma), because DS raises linearly to the ratio [-OH(PVA)/GMA] up to 25 mol-% and the respective yield ranged from 83 to 92 %. It is difficult to obtain more than 50 mol-% substitution of PVA hydroxyl by methacryloyl groups even in these optimized conditions due to increased steric hindrance by the large number of the methacryloyl groups inserted into PVA.
Preparation and characterization of post-derivatives from functional polystyrene (ATRP) with p-nitroanilineazomethine phenol and their thermal and optical study
Authors: Yu Xifei , Zhang Guo , Shi Tongfei , Dutta P.K. , An Lijia
Published: August 2014

The functional polystyrene, (Cl-PS)2-CHCOOCH2CH2OH (designated as XPSt and coded P2) was prepared by ATRP at 1300C using CuCl and bipyridine as catalysts, 2,2-dichloro acetate-ethylene glycol (DCAG) as multifunctional initiator and THF as solvent. 4-Nitoroaniline azomethine-4’ phenol (P1) as chromophores were covalently linked to the functional end groups of the polymer by using simple displacement reaction. The functional polystyrenes, namely XPSt (P2) and (PS)2-CHCOOCH2CH2OH, designated as X-PSt and coded P3 and their post-derivatives, namely, DXPSt (P4) and DX-PSt (P5) respectively were characterized by IR, NMR and UV spectroscopies, gel permeation chromatography (GPC) and thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), polarising optical microscopy (POM) and XRD studies. DSC showed that incorporation of chromophores in the side chains of polymers towards the polystyrene moiety increases the rigidity of the polymer and subsequently, its glass transition temperature; however the incorporation of side chain towards the alcoholic functional group decreases the glass transition temperature. The post derivatives do not play any significant role to increase the thermal stability (TGA). There was evidence for liquid crystalline properties in the resulting polymer derivative DXPSt (P4) as observed from POM study, which defines the alignment of chromophores into the polymers. The XRD study shows crystalline behaviour of the polymer derivative, P4. The polymer derivative, DXPSt (P5) does not show such behaviour and this may be due to the bonding of azomethine towards the short chain alcoholic telechelic alcoholic sides of the copolymer.
Modification of poly(L-lactic acid) with L-lactic acid / citric acid oligomers
Authors: Jiang Yan , Bai Yun , Chen Man , Yao Fanglian , Zhang Haiyue , De Yao Kang
Published: August 2014

The surface modification of polymeric biomaterials can be achieved by surface immobilization of bioactive molecules, increased hydrophilicity, and balanced hydrophilicity and hydrophobicity. Poly (L-Lactic Acid) (PLLA) is hydrophobic and possesses no reactive groups in the structure. In the present work, an effort has been made to blend PLLA with functionalized L-lactic acid / citric acid oligomer (PLCA) in order to improve the hydrophilicity of the PLLA. The compatibility of PLLA and PLCA was studied by using differential scanning calorimetry (DSC). The blends were also characterized for their water absorption, contact angle, tensile strength and hydrolytic degradation. The DSC results showed that PLLA/PLCA blends exhibited a single glass transition temperature (Tg), which lies in between that of PLLA and PLCA, thus asserting compatibility at the molecular level. The studies on water absorption, contact angle and hydrolytic degradation showed that addition of PLCA to PLLA enhanced the hydrophilicity of PLLA.
Effect of Nematic Order Coupling on the Phase Diagrams of Side-Chain Polymer Gels with Liquid Crystal Solvent
Authors: Vendamme Richard , Maschke Ulrich
Published: August 2014

We have explored the influence of nematic order coupling on the swelling and phase diagram of polymer networks in nematogenic low molar weight LC solvent, in view of the increasing importance of such systems in advanced optical devices. Firstly, one isotropic polyacrylate network and one nematic sidechain polyacrylate network is prepared. Immersing these two networks in nematic LC solvent lead to the formation of well-defined polymer gels with LC solvents and allow us to establish the phase diagram of these relatively new materials in the concentration-temperature frame. Results were critically analysed as a function of temperature and network nature (isotropic or nematic). We demonstrate that in the case of gel made from an isotropic polymer network, the LC solvents fails to form a nematic phase inside the gel due to the lack of anisotropic coupling. Moreover, in that case the gel shrinks below TNI Solvent because of a strong “entropic” incompatibility between the isotropic flexible coils and the LC nematogens. However, the situation is drastically different in the case of LC side-chain network due to a strong coupling of the nematic order between the mesogens of the solvents and those of the polymer backbone. In that case, tremendous distortions appear in the phase-diagram, in which we especially emphasize the apparition of a stable nematic gel phase and a miscibility gap between TNI Solvent and TNI Gel. Finally, results are critically examined and compared to the few studies found in the literature.
One-pot synthesis of PMMA/montmorillonite nanocomposites
Authors: Kiersnowski Adam , Trelinska-Wlazlak Maria , Dolega Justyna , Piglowski Jacek
Published: August 2014

This article describes simple preparation methods of poly(methyl methacrylate) (PMMA)/synthetic montmorillonite nanocomposites by single-step insitu polymerizations. Compatibility between PMMA and the silicate was ensured by an addition of (3-acrylamidepropyl) trimethylammonium chloride (AAPTMA). The work also compares how different synthetic routes, namely emulsion and solution polymerization, affect the structure as well as thermal and mechanical properties of obtained nanocomposites. The results of structural investigations clearly show, that both the techniques lead to intercalated nanocomposites, but emulsion polymerization allows more effective deflocculating and intercalating of the clay with acrylic copolymers. The addition of small amounts of layered silicates causes an increase in thermal stability and stiffness of the materials. It is demonstrated that at 5 wt. % of the filler, the temperature of 10 % weight loss was shifted up by nearly 50 K in comparison to the neat PMMA. In the same sample, the Young’s modulus of the material was found to be increased by 26 %.
Dynamic Simulation and Modelling of Bulk Polymerization of Ethylene Using Bi-functional initiators
Authors: Gharagheizi Farhad
Published: August 2014

A dynamic simulation and modelling of ethylene bulk polymerization in an autoclave reactor are presented in this paper, based on a kinetic model. This simulation is done for mono- and bi-functional initiators, and results show that application of the bi-functional initiators cause an increase in ethylene conversion. The presented model shows very good results for high temperature and low temperature, in comparison with experimental data in the literature.
Surface-Ionized thermosensitive poly(N-isopropylacryl amide) hydrogels with faster response
Authors: Xin-Cai Xiao
Published: August 2014

Poly(N-isopropylacrylamide) hydrogels have been successfully modified by concentrated sulfuric acid for the first time. The modified hydrogels displayed faster, larger magnitude and hydration/dehydration dynamic response to temperature cycling without increasing the lower critical solution temperature (LCST). These contributions were attributed to sulphate ester groups resulting from terminal hydroxyl groups of poly(N-isopropylacrylamide). These results may lead to technological application for temperature-responsive thin film and microgel particles with higher surface-to-volume ratio.
Synthesis and characterization of poly(ethylene-vinyl alcohol)-g-poly(phenyl ethyl methacrylate) copolymers by a grafting onto method
Authors: Azam M. , John V. Dawkins
Published: August 2014

Graft copolymers of poly(ethylene-vinyl alcohol)-g-poly(phenyl ethyl methacrylate) copolymers were prepared by a grafting onto method in two steps. In the first step carboxyl terminated poly(phenyl ethyl methacrylate) (PPHETMA) were prepared by solution radical polymerization using 4,4-azobis(cyanovaleric acid) (ACVA) as initiator and thioglycolic acid (TGA) as matched chain transfer agent and then converting carboxyl groups into acid chloride terminated prepolymer by reacting with oxalyl chloride. In the second step acid chloride terminated prepolymers were reacted to the ethylene-vinyl alcohol (EVOH) backbone. Grafting was confirmed by Size Exclusion Chromatography (SEC), Fourier Transfer Infrared spectroscopy (FTIR) and Nuclear Magnetic Resonance (NMR) spectroscopy. Thermal properties of the graft copolymers were studied by Differential Scanning Calorimetery (DSC) and Dynamic Mechanical Thermal Analysis (DMTA).
Dynamics of Complexation of a Charged Dendrimer by Linear Polyelectrolyte: Computer Modelling
Authors: Lyulin Sergey , Darinskii Anatolij , Lyulin Alexey
Published: August 2014

Brownian-dynamics simulations have been performed for complexes formed by a charged dendrimer and a long oppositely charged linear polyelectrolyte when overcharging phenomenon is always observed. After complex formation the orientational mobility of the individual dendrimer bonds, the fluctuations of the dendrimer size, and the dendrimer rotational diffusion have been simulated. Corresponding relaxation times do not depend on the linear-chain length in a complex and are close to those for a single neutral dendrimer. At the same time fluctuations of the size of a complex are completely defined by the corresponding fluctuations of a linear polyelectrolyte size. Adsorbed polyelectrolyte practically does not feel the rotation of a dendrimer; simulated complexes may be considered as nuts with light core (dendrimer) and heavy shell (adsorbed linear polymer); the electrostatic contacts between dendrimer and oppositely charged linear polymer are easily broken due to the very fast dendrimer-size fluctuations.
Kinetics modeling of the reaction for an Epoxy/PMMA/MMT ternary system
Authors: Hernandez Marcelo , Dupuy Jérôme , Duchet Jannick , Sautereau Henry
Published: August 2014

The effect of thermoplastic PMMA and clay Cloisite 30B addition on the cure kinetics of an epoxy/amine thermosetting system was investigated using differential scanning calorimetry (DSC) and modelled using a single kinetic model. For obtaining a good agreement between the experimental results and theoretical modeling, it was necessary to separate the ternary system in two formulations: matrix/PMMA and matrix/clay systems. It appeared that the addition of PMMA delays the reaction up to the phase separation phenomenon due to a dilution effect of the reactive species. In opposition, the presence of clays accelerates the reaction (probably due to a catalytic effect of some metals ions introduced with the clay) but it has no sensitive effect on the cloud point conversion in the presence of PMMA. The modeling results are in good agreement with those experimentally obtained.
Polyaniline-modified Montmorillonite Nanocomposite as an Actuator
Authors: Golmohammadi Masumeh , Kokabi Mehrdad , Entezami Ali Akbar
Published: August 2014

Polymer actuators have received much attention due to their vast potential applications. In this work the preparation of polyaniline nanocomposite actuator is studied. The main objective is to overcome the disadvantages of pristine polyaniline in thermal, mechanical and electroactive properties. Montmorillonite is the best candidate for this purpose. Various polyaniline/modified montmorillonite nanocomposite films were prepared using solution method. The properties of nanocomposites are characterized by X-ray diffractometry, transmission electron microscopy, thermal gravimetric analysis, dynamic mechanical analysis, conductivity measurement and cyclic voltammeter. The effects of actuator length and applied scan rate as well as the response of applied potential in actuating applications were investigated. The results show that the structure of nanocomposite is exfoliated. Adding organoclay to polyaniline matrix regardless of decreasing its conductivity; increases the stiffness of the actuator resulting in lower bending level in a linear manner. It reduces the required time to reach the maximum bending, also recovery bending time, i.e. actuator response. Increasing the applied scan rate decreases the actuator bending. Also increasing the length of actuator increases the amount of nanocomposite actuator bending in a linear manner.
Static light scattering and transmission microscopy study of dilute Nafion solutions
Authors: Wen-Hong Liu , Ting-Yi Yu , Yu T. Leon , Hsiu-Li Lin
Published: August 2014

Nafion, an ionomer composed of perfluorocarbon backbone and vinyl ether side chains terminated with -SO3 - groups, has dual solubility parameters, i.e. δ1= 9.7 (cal/cm3)1/2 relating to perfluorocarbon backbones and δ2 = 17.3 (cal/cm3)1/2 relating to sulfonated vinyl ether side chains. It had been reported that Nafion molecules aggregated in dilute and semi-dilute water and alcohol solutions. In this study, we report static light scattering (SLS) measurements of dilute Nafion in N,N’- dimethyl formamide (DMF, solubility parameter δ =12.2 (cal/cm3)1/2, dielectric constant ε=36.7) and N,N’-dimethyl acetamide (DMAc, δ =10.8 (cal/cm3)1/2, ε=37.8) solutions with Nafion concentrations ranging from 0.2 mg/ml to 1.0 mg/ml. The DMF and DMAc solvents have δ closing to δ1 of Nafion perfluorocarbon backbones and ε much lower than water (ε =78). Thus DMF and DMAc are compatible with Nafion perfluorocarbon and few Nafion molecules aggregate in DMF and DMAc solvents when [Nafion]< 1.0 mg/ml. The lower ε of DMF and DMAc led to low polyelectrolyte effect of Nafion in these two solvents. The obtained Mws of present work were in good agreement with the Mw obtained from Nafion in dilute dimethyl sulfoxide (DMSO, δ =12.0 (cal/cm3)1/2, ε=46.6) solutions, reported by Lousenberg, using size exclusion chromatography incorporating static light scattering detection. The  data obtained from SLS measurements were compared with the particles sizes of transmission electron microscope (TEM) observations of freeze dried Nafion thin films prepared on copper grids with 0.6 mg/ml Nafion solutions. Comparable results were obtained from these two observations.