bluuebunny/crossref_metadata_2025_split huggingface dataset:
Poly(η-caprolactone) layered silicate nanocomposites: effect of clay surface modifiers on the melt intercalation process
Authors: Pantoustier Nadège , Alexandre Michaël , Degée Philippe , Calberg Cédric , Jérôme Robert , Henrist Catherine , Cloots Rudi , Rulmont André , Dubois Philippe 
Published: August 2014

AbstractNanocomposites based on biodegradable poly(e-caprolactone) (PCL) and layered silicates (montmorillonite) modified by various alkylammonium cations were prepared by melt intercalation. Depending on whether the ammonium cations contain non-functional alkyl chains or chains terminated by carboxylic acid or hydroxyl functions, microcomposites or nanocomposites were recovered as shown by X-ray diffraction and transmission electron microscopy. Mechanical and thermal properties were examined by tensile testing and thermogravimetric analysis. The layered silicate PCL nanocomposites exhibited some improvement of the mechanical properties (higher Young’s modulus) and increased thermal stability as well as enhanced flame retardant characteristics as result of a charring effect. This communication aims at reporting that the formation of PCL-based nanocomposites strictly depends on the nature of the ammonium cation and its functionality, but also on the selected synthetic route, i.e. melt intercalation vs. in situ intercalative polymerization. Typically, protonated w-aminododecanoic acid exchanged montmorillonite allowed to intercalate ε -caprolactone monomer and yielded nanocomposites upon in situ polymerization, whereas they exclusively formed microcomposites when blended with preformed PCL chains. In other words, it is shown that the formation of polymer layered silicate nanocomposites is not straightforward and cannot be predicted since it strongly depends on parameters such as ammonium cation type and functionality together with the production procedure, i.e., melt intercalation, solvent evaporation or in situ polymerization.
(9,9-Dialkylfluorene-co-fluorenone) copolymers containing low fluorenone fractions as model systems for degradation-induced changes in polyfluorene-type semiconducting materials
Authors: Scandiucci de Freitas Patricia , Scherf Ullrich , Collon Maximilien , List Emil J. W. 
Published: August 2014

AbstractThis short communication describes synthesis, optical and electronic properties of novel 9,9-dialkylfluorene-co-fluorenone copolymers which function as model systems for degradation-induced changes in polyfluorene-type semiconducting materials. Only very small fractions of incorporated fluorenone building blocks lead to a dramatic change of the solid state properties (photo- and electroluminescence). The results are discussed in terms of intra- vs. intermolecular excitation energy transfer.
Simulation of bubble growth and collapse in linear and pom-pom polymers
Authors: Agarwal Uday S. 
Published: August 2014

AbstractExisting approaches to simulate the bubble growth/collapse in viscoelastic liquids use the integral form of a constitutive equation, that can additionally be analytically integrated over the radial domain. Here we represent the process by a system of simultaneous partial differential equations, with fixed and finite boundaries. This enables a direct computer implementation with commercially available software, with little additional programming effort. The involved co-ordinate transformation preferably does not correspond to the material co-ordinates. The surrounding liquid can be simulated as being a finite film or of infinite extent, with simply a change in one computational parameter. We simulate hydrodynamically induced bubble dynamics in viscolelastic liquids, and estimate the flow strength (elongational strain rate) and its possible role in flow induced scission of polymer chains in liquids experiencing bubble collapse. Calculations are also performed to evaluate the influence of backbone and branch lengths when the surrounding fluid is a branched polymer melt, using the pom-pom model to describe the rheological behavior.
Formation and blood compatibility of thin layers of hyperbranched polymers on polyurethane films
Authors: Park Yong Soon , Kang Yong Soo , Chung Dong June 
Published: August 2014

AbstractTwo kinds of hyperbranched polymers, star-shaped poly(ethylene oxide) and poly(2-ethyl-2-oxazoline)-bound polyamidoamine dendrimer, were immobilized on polyurethane (PU) films using photoreactive azidophenyl groups. Immobilization of the hyperbranched polymers was verified by ATR FT-IR observations and contact angle measurements. Using photoreactive molecules, this study shows a unique method to modify polymer films without functional groups easily through immobilization of other polymers on the film surface. PU surfaces modified with immobilized hyperbranched polymer showed significantly reduced platelet adhesion, i.e. increased blood compatibility, as measured via UV spectrometry and scanning electron microscopy.
Copolymerization of styrene with methyl-substituted styrenes in the presence of titanium monometallocenes
Authors: Oliva Haydée , Leal Gracia , Ismayel Alida , Arribas Guillermo , Bronco Simona 
Published: August 2014

AbstractThis paper investigates the homo- and copolymerization of styrene with p-methylstyrene, m-methylstyrene, 2,4-dimethylstyrene, 2,5-dimethylstyrene and 2,4,6-trimethylstyrene using a Cp*TiCl3 (Cp: cyclopentadienyl) semimetallocene catalyst activated with methylaluminoxane. Syndiotactic homo- and copolymers were obtained only for the monosubstituted monomers. For the di- or trisubstituted monomers, reduced reactivities, stereoregularities, and degrees of polymerization were obtained with respect to the monosubstituted monomers. More specifically, the homopolymerization of 2,5-dimethylstyrene and 2,4,6-trimethylstyrene and their copolymerization with styrene was inhibited. The reason for this are combined steric and inductive effects. The presence of methyl groups in para position seems to inhibit crystallization of the syndiotactic polymers. In contrast, crystallinity was evidenced in the materials produced in the presence of m-methyl substituted monomers.
Flocculation characteristics of organo-modified clay particles in poly(L-lactide) / montmorillonite hybrid systems
Authors: Nam Pham Hoai , Fujimori Atsuhiro , Masuko Toru 
Published: August 2014

Abstract The stacking characteristics of organo-modified montmorillonite particles in poly(L-lactide) / clay hybrids have been investigated through FT-IR measurements and transmission electron microscopy. The clay particles tend to flocculate with hydrogen bonding among the hydroxyl groups of the surfactant, those located at the edge of clay particles, and/or those existing at the ends of polylactide chains.
Optical methods to study the behaviour of supported metallocene catalysts during olefin polymerisation
Authors: Jang Yong-Jun , Bieber Kirsten , Naundorf Corinna , Nenov Nikolay , Klapper Markus , Müllen Klaus , Ferrari Daniela , Knoke Stefan , Fink Gerhard 
Published: August 2014

AbstractIt is demonstrated that modern optical methods allow for a very fast study of the behaviour of supported metallocene catalysts. By videomicroscopy several polymeric supports functionalised with cyclopentadiene units or poly(ethylene oxide) and poly(propylene oxide) chains and loaded with a metallocene were simultaneously studied. In this example it is shown that this method allows for a direct comparison of different catalysts under identical conditions in a single experiment. In addition by this experiment more detailed information on the behaviour of the supports can be obtained by studying the growth kinetics of single grains. As a second tool, laser scanning confocal fluorescence microscopy (LSCFM) was applied. Using dye-labelled supports LSCFM can be used as a very rapid tool to study the fragmentation of supports. This is demonstrated by 3D images showing the distribution of different support fragments in the polyethylene product particles.
Use of mesoporous silica as a reinforcing agent in rubber compounds
Authors: López Betty L. , Pérez León Dario , Mesa Mónica , Sierra Ligia , Devaux Eric , Camargo Mauricio , Campagne Christine , Giraud Stéphane 
Published: August 2014

AbstractMesoporous silica is used as filler for styrene-butadiene rubber (SBR); filler-polymer interactions are compared with those exhibited when Ultrasil silica (VN3) is used. A silane coupling agent is added to improve filler dispersion and its influence on the bound-rubber formation is also investigated. The bound-rubber content is higher for the mesoporous silica and increases further for the sample containing silane. The increase is explained by chemical interactions between filler and rubber and penetration of the rubber chains into the mesopores. This is confirmed by 13C solid-state NMR, IR spectroscopy and differential scanning calorimetry. Dynamic mechanical thermal analysis shows higher storage modulus for the rubber filled with mesoporous silica.
Thermo-responsive polymers and hydrogels in tissue engineering
Authors: Schmaljohann Dirk 
Published: August 2014

AbstractVarious aspects of synthetic polymers and hydrogels in tissue engineering are discussed. A series of graft copolymers based on either N-isopropylacrylamide or N,N-diethylacrylamide as polymer backbone, and on poly(ethylene glycol) as side chain were prepared and characterized. These polymers were then used for the preparation of surface-immobilized hydrogels. The thermo-responsive behaviour was studied on model substrates by ellipsometry. The use of thermoresponsive polymers for in vitro studies allows the control of surface properties and thus the stimulation of cell adhesion and detachment through temperature changes. The cellular response was investigated by cultivation of mouse fibroblasts on surface-immobilized, thermo-responsive hydrogels. It was demonstrated that mouse fibroblasts adhere and detach as a function of the temperature, which then could be related to the change in surface properties. The concept is finally extended to the preparation of patterned hydrogels, which were studied by imaging ellipsometry.
Poly(vinyl alcohol) nanofibres by electrospinning: influence of molecular weight on fibre shape
Authors: Jun Zeng , Hou Haoqing , Wendorff Joachim H. , Greiner Andreas 
Published: August 2014

AbstractPoly(vinyl alcohol) (PVA) nanofibres were obtained by electrospinning of PVA/water solutions. Formation of beaded fibres combined with decreased fibre diameters was observed for low PVA concentrations. Electrospinning of blends of PVA of different molecular weight resulted in less bead formation and smaller fibre diameters as compared to corresponding homopolymers of similar viscosity.
Development of high-temperature separation techniques for the chemical composition analysis of ethylene - methyl methacrylate block copolymers
Authors: Heinz Lars-Christian , Graef Sven , Macko Tibor , Brüll Robert , Balk Sven , Keul Helmut , Pasch Harald 
Published: August 2014

AbstractEthylene - methyl methacrylate block copolymers are semicrystalline polymers that dissolve in organic solvents only at high temperatures. Accordingly, microstructure analysis by solution methods must be conducted at temperatures above 130°C. For the analysis of block copolymers of different compositions several analytical techniques were used, including high-temperature size-exclusion chromatography (SEC), hyphenated SEC-FTIR, and CRYSTAF (crystallisation analysis fractionation). While SEC with refractive index detection indicated a certain multimodality of the samples, SEC coupled with FTIR revealed that the samples were chemically inhomogeneous and may contain homo- and copolymer fractions. The presence of polyethylene and poly(methyl methacrylate) homopolymers in the copolymer samples was confirmed by CRYSTAF analysis, when the total concentration as well as the carbonyl group distribution were monitored separately. Chromatographic separation of the different sample components was achieved when liquid chromatography at critical conditions (LC-CC) was used. For the first time, true high-temperature LC-CC methods were developed operating at a column temperature of 140°C. As the stationary phase, silica gel was used. Suitable mobile phases were binary mixtures of 1,2,4-trichlorobenzene or 1,2- dichlorobenzene with cyclohexanone. Using LC-CC, the samples were separated into the copolymer and the homopolymer fractions.
Effect of organoclay impurities on mechanical properties of EVA-layered silicate nanocomposites
Authors: Bellucci F. , Camino G. , Frache A. , Ristori V. , Sorrentino L. , Iannace S. , Bian X. , Guardasole M. , Vaccaro S. 
Published: August 2014

AbstractThe purification process of commercial organoclays and the beneficial effect of the impurities removal on the mechanical properties of the EVA exfoliated and intercalated nanocomposites are described in this paper. Mechanical properties such as Young modulus are improved, without any change in morphology in the exfoliated nanocomposites and an improvement of intercalation degree in the intercalated nanocomposite as demonstrated by rheological test is observed.
Modification of NR/BR blend with unsaturated thermo plastic polyurethane; polyurethane synthesis, blend morphology, vulcanization, and vulcanizate properties
Authors: Šebenik Urška , Poljanšek Ida , Krajnc Matjaž 
Published: August 2014

AbstractThe unsaturated polyurethane (PU) was synthesized, characterized, and used in rubber compound. To study the effect of PU incorporation in the blend a systematic approach was used where PU was added to the natural rubber (NR), butadiene rubber (BR), and NR/BR blends. Different un-vulcanized and vulcanized compounds were characterized and the vulcanization process was investigated. It was observed that the synthesized PU was able to crosslink with the rubber compounds during the vulcanization process. The lowered temperature of melting indicated a better processability of the composites containing thermoplastic PU which melted at processing temperature, thereby allowing improvement in blend viscosity mold flow and to some extent in its homogeneity, although the mechanical properties such as hardness, tensile strength, modulus, and elongation at break did not differ significantly from the properties of elastomer blends without PU. The thermal stability of compounds with PU did not significantly worsen.
Hyperbranched Polymers from Maleic Anhydride and Diethanolamine: Synthesis, Characterization and Solution Rheology
Authors: Song Weiqiang , Song Qinghuan , Wu Chengxun 
Published: August 2014

AbstractNovel hyperbranched polyesteramides have been synthesized from diethanolamine and maleic anhydride with ethylene glycol as a core monomer. No gelation occurred in the melt polymerization when diethanolamine and maleic anhydride were used in equimolar amount in the feed and when content of ethylene glycol was varied. Obtained products were soluble in water and in organic solvents such as NMF. The obtained polymers were characterized by using IR and NMR spectroscopies as well as GPC. It was suggested that the hyperbranched polyesteramides formed via a mechanism of a combination of esterification and addition reactions. The addition of a hydroxyl group to the - CH=CH- in maleic anhydride unit results in a formation of CH methine group. The ratio of -CH=CH- to CH in the polymers were estimated from 1H NMR spectrum as 0.140, 0.155, 0.175, 0.190 and 0.204 for polymers P1 to P5, respectively as the content of ethylene glycol charged decreased. The molecular weights and their polydispersities showed reverse dependences on the feed ratio of ethylene glycol to diethanolamine. The rheological properties of the polymers in aqueous solution were also examined. The polymers exhibit a steady increase of intrinsic viscosity with increasing molecular weight, and the Mark-Houwink exponent for these polymers is 0.26, which is much lower than 0.5 and suggested that these polymers possess a highly branched architecture. The polymer solutions showed a Newtonian behavior with steady shear viscosities independent of shear rate, which indicated the absence of a physical entanglement.
Variable morphologies of poly(vinyl acetate)–montmorillonite nanocomposites obtained by emulsion polymerization in the presence of poly(vinyl pyrrolidone)
Authors: Corobea Mihai-Cosmin , Uricanu Violeta , Donescu Dan , Deladi Szabolcs , Radovici Constantin , Serban Sever , Constantinescu Elena 
Published: August 2014

AbstractNanocomposites containing poly(vinyl acetate) and montmorillonite (MMT) were prepared using a one-batch emulsion polymerization recipe, assisted by poly (vinylpyrrolidone). The relative clay concentration with respect to the other reaction partners influences drastically the morphological units in the end-products. For low [MMT], well-defined, spherical PVAc particles are formed. At the other extreme, for high [MMT], production of polymeric, water-swollen aggregates is favored. Depending on the MMT/PVP ratio, the clay will be dispersed in the final polymer matrix in variable forms, from individual platelets to agglomerates of reformed tactoids.
Synthesis and characterization of new phenanthrolinetriether copolymers with rotaxane architecture
Authors: Farcas Aurica , Harabagiu Valeria 
Published: August 2014

AbstractThis paper is devoted to the preparation and characterization of new phenanthroline-triether copolymers with rotaxane architecture by reaction of complexes of α- or β- cyclodextrin and tri(ethylene glycol) ditosylate with 2,9-di(4-hydroxyphenyl)-1,10- phenanthroline, which is large enough to prevent dethreading of cyclodextrin molecules. Comparative 1H-NMR analysis of tri(ethylene glycol) ditosylate complexes and of rotaxane copolymers evidenced the lower cyclodextrin content in rotaxane copolymers as compared to the calculated values. The rotaxane copolymers present bimodal molecular weight distributions attributed to the separation of the fractions with different content of cyclodextrin threaded on the copolymer chain. As evidenced by thermogravimetric analysis, the rotaxane copolymers show higher thermal stability than its non-complexed homologue.
Synthesis and characterization of carboxyl endfunctionalized poly(methylidene malonate 2.1.2)
Authors: Studer Peggy , Riess Gérard 
Published: August 2014

Abstractα-Carboxyl end-functionalized poly(methylidene malonates 2.1.2) were prepared by free-radical polymerization in the molecular weight range 5 000 - 10 000 by using 4,4'-azobis(4-cyanopentanoic acid) as a functional initiator. A functionality of one carboxyl group per chain could be obtained. On the contrary, it was demonstrated that chain transfer functionalization with mercaptans is not applicable in this case. A Michael addition reaction between the mercaptan and the monomer becomes the predominant side-reaction. The corresponding mercaptanmonomer adduct was characterized in detail by 1H and 13C NMR.
The free volume in two untreated, pressure-densified, and CO2 gas exposed polymers from positron lifetime and pressure-volume-temperature experiments
Authors: Dlubek Günter , Pionteck Jürgen , Shaikh Muhamad Qasim , Häußler Liane , Thränert Stefan , Hassan E. M. , Krause-Rehberg Reinhard 
Published: August 2014

AbstractChanges in the microstructure of the free volume and its temperature dependence in ethylene-norbornene copolymer and bisphenol-A polycarbonate due to densification under pressure and swelling with CO2 gas have been examined using positron annihilation lifetime spectroscopy (PALS) and pressurevolume- temperature (PVT) experiments. Employing the Simha-Somcynsky equation of state the specific hole free and occupied volumes were estimated. From the PALS spectra analyzed with the new routine LT9.0 the size distribution of subnanometre holes and its mean and mean dispersion were calculated. Above Tg, the dispersion mirrors the thermal fluctuations in the free volume. From comparison of PALS and PVT data the specific number of holes was estimated. It was found that the occupied volume has a constant and identical compressibility in the glassy and rubbery state. It shows no memory for the history of the glass and mirrors only the pressure and temperature during the measurement. The change in the total volume due to the pre-treatments of the polymers occurs exclusively in the hole free volume Vf and the relative change in Vf is one order of magnitude larger than in the total volume. PALS data show that the mean hole size and its dispersion in the glassy state is decreased due to densification and increased due to swelling. PVT data show that the volume changes are frozen in the polymer glasses and that, when heating the samples, the volume begins to recover at temperatures ca. 50 K in gas swollen and 20 K in densified polymers below Tg. The PALS data show a corresponding behaviour.
Solvency effect of the dispersion medium on the radical polymerization of styrene in non-aqueous dispersion media
Authors: Ahmad Hasan , Chaki Bijan Mohon , Rahman M. Mahbubor , Miah M.A. Jalil , Tauer Klaus 
Published: August 2014

AbstractRadical dispersion polymerization of styrene in a non-aqueous media in the presence of a solvent for polystyrene was carried out to study the effect of the solvency of the continuous phase on the polymerization kinetics, the particle morphology, the size and the particle size distribution. Either ethylacetate or cyclohexanone was used as solvent in combination with ethanol as non-solvent. The polymerization kinetics is strongly influenced by the solvency of the continuous phase. The rate of polymerization is reduced in the ethanol-cyclohexanone mixture almost by a factor of two relative to the value obtained in the ethanol-ethylacetate system. On the contrary, variations in the initiator and stabilizer concentration have negligible effects on the polymerization kinetics.
Modelling leading to water entrapment point in thermally driven hydrogelation of methyl cellulose
Authors: Joshi Sunil C. , Lam Y.C. , Bin Chen 
Published: August 2014

AbstractDevelopment of descriptive models for thermally-driven gelation process for methyl cellulose (MC) solutions is presented in this paper. The available heat absorption profiles obtained using a micro-differential scanning calorimeter (μDSC) during the gelation of MC (SM4000) aqueous solutions with various concentrations were examined. Different mathematical models were considered for fitting the experimental data. Necessary constants for the proposed mathematical formulations were obtained based on the DSC measurements to achieve the most promising fit. Further, analysis based on the mathematical models was performed to describe influence of various parameters for the gelation process, including the total heat, the degree, and the state of gelation. The effect of variations in MC concentrations on these parameters was investigated and the possible mechanisms were highlighted. Proposition was made towards the existence of a water entrapment point on the degree of gelation plots of MC hydrogels and its significance was discussed.
Polypropylene based carbon nanotubes composites: structure and properties
Authors: Tabuani Daniela , Granelli Walter , Camino Giovanni , Claes Michael 
Published: August 2014

AbstractIn the field of polymer nanocomposite materials, carbon nanotubes have attracted lots of research interests in the recent past for their potentialities in improving a wide range of polymer properties. We present here a comprehensive study on polypropylene/carbon nanotube composites evaluating the morphology as well as the thermal behaviour of the prepared systems. Pristine as well as -COOH functionalised carbon nanotubes were taken into account and melt mixed at different weight fractions with PP; the crystallisation characteristics of the material were evaluated by means of DSC and XRD and the thermal behaviour was assessed through TGA analyses. The nanotubes appear to affect significantly the properties of the matrix in a way notably dependent on the functionalization and on the filler amount.