bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the autoaccelerated character of the branched oxidation of polyolefins
Authors: Verdu Jacques 
Published: March 2011

AbstractPhotochemical or thermal (at moderate temperatures) oxidation of hydrocarbon polymers is characterised by the existence of a pseudo‐induction period, during which oxidation is autoaccelerated, and a steady state. This latter corresponds to the equilibrium between hydroperoxide (POOH) decomposition and formation processes. All the kinetic schemes of thermal ageing, based on the assumption that POOH decomposition is the only source of radicals (whatever its order), have a common feature : the steady‐state rate is independent of the rate constant of POOH decomposition, as experimentally observed in samples containing variable concentrations of catalytic residues.Experimental data indicate that the duration of the pseudo induction period is proportional to the reciprocal of the POOH decomposition rate constant and independent of any other rate constant. This is an exclusive property of kinetic schemes in which POOH decomposition is unimolecular (whereas termination is bimolecular). The corresponding set of differential equations has been first resolved from the hypothesis of existence of a stationary state for radical concentration. Although this hypothesis is questionable, the corresponding analytical expression appears as a good approximative solution for the general case (no hypothesis of stationary regime). This expression displays interesting predictive properties. Some eventual kinetic implications of spatial heterogeneity of oxidation are examined. Certain variables, for instance the second derivative of the kinetic curve of carbonyl growth (or oxygen absorption), or simply the kinetic curve of mass variation, vary in a non‐monotonous way with exposure time. Consideration of timescale associated to these variations can lead to a quantitative approach of the homogeneity. Schematically, if the characteristic time of non‐monotonous variations is of the order of magnitude of the reciprocal of the rate constant of POOH decomposition or lower, the oxidation can be considered almost homogeneous. In the example under study : experimental data on thermal oxidation of poly(propylene) indicate that these systems are not too far from homogeneous ones.
Stabiliser partitioning and oxidative degradation in rubber‐toughened polypropylene
Authors: Billingham Norman C. , Hoad Oliver J. , Chenard François , Whiteman David J. 
Published: March 2011

AbstractSolubility measurements on an antioxidant and a UV stabiliser in polypropylene and an ethylene/propylene rubber are correlated with partitioning between the two bulk polymers and between the phases of a blend. At low concentrations, partitioning concentrates the additive in the rubber; the effect increases with temperature, so that most of the additive will be in this phase at processing temperatures. Calculations suggest that the additives can diffuse between phases fast enough to compensate for consumption in either at service temperatures. At processing temperatures, diffusion of antioxidant from the more stable rubber phase to the polypropylene phase may be slow enough to limit protection from oxidation.
Chromatic changes in the blends of electroactive polymers with comb‐shaped flexible polymers
Authors: Kim Myoung Soo , Levon Kalle 
Published: March 2011

AbstractThe effect of blending of alkylated polymers, which have different backbone structures, was investigated in order to improve the electronic properties of conducting polymers. Comb‐shaped flexible polymer, poly(octadecyl acrylate) (PODA), was blended with rigid alkylated conducting polymers, poly(3‐dodecyl‐thiophene)(PDDT), and polyaniline emeraldine base (PANI)/p‐dodecyl‐benzenesulfonic acid (DBSA) complex, respectively, to investigate the effect of long alkyl chain of flexible polymer on the conformational mode change of rigid backbones and the effect of intermolecular interaction between these alkylated polymers. Optical microscopy was applied to observe the morphology change and obtain the phase diagrams of these blends. The intermolecular interactions that occurred in these blends were explained for each different characteristic peak obtained with FT‐IR spectra. Solvatochromism (red‐shift) of PDDT/PODA binary blends in solid state due to the planarity change of rigid backbone in the presence of PODA and electrochromism of PANI(DBSA)4/PODA ternary blends due to the hydrogen bonding between the nitrogen cation of PANI complex and carbonyl group of PODA are observed in UV‐Vis‐NIR spectra. Interestingly, the increase of conductivity was observed in the presence of 5 wt% of PODA in PDDT/PODA binary blends and a homogeneous smectic liquid crystalline structure was clearly confirmed by cross polarized optical microscopy in PANI(DBSA)4/PODA ternary blends.
Charge transfer interactions in liquid crystalline polymers probed by fluorescence spectroscopy
Authors: Horie Kazuyuki , Huang Hsuwen , Sone Masato , Watanabe Junji 
Published: March 2011

AbstractRigid‐rod aromatic LC polyester with long alkyl side chains and two thermotropic LC polyesters (PET40/OBA60 and PB‐10) were studied by fluorescence spectroscopy to investigate their charge transfer interactions corresponding to LC configuration and changes during phase transition.
Thermodynamic order and random disorder in liquid crystal elastomers
Authors: Terentjev Eugene M. 
Published: March 2011

AbstractThis article focuses on the continuum aspects of liquid crystal elastomer structure. There are two opposing tendencies, the lack of thermal fluctuations that enhances the order in the system, and the random quenched disorder that leads to a highly frustrated polydomain state in equilibrium. Imposing an external field (mechanical stress) changes the balance between order and disorder, this process being monitored by a polarised light scattering.
Interplay of ionic and nonionic interactions in weakly charged polyelectrolytes
Authors: Khokhlov Alexei R. , Makhaeva Elena E. , Zeldovich Konstantin B. 
Published: March 2011

AbstractWe describe the results of theoretical and experimental studies of the regular heterogeneities on a nanometer scale which are formed in the systems containing weakly charged polyelectrolytes due to the competition of ionic and hydrophobic interactions. In particular, we consider the effect of microphase separation in poor solvent polyelectrolyte solutions and gels and nano‐self‐assemblies emerging in the complexes of polyelectrolyte gels with oppositely charged surfactants. The practically important application connected with metal nanoparticles formation in regular microstructures in polyelectrolyte systems is considered as well.
Influence of crystallinity on the morphology of poly(ethylene oxide) containing diblock copolymers
Authors: Hillmyer Marc A. , Bates Frank S. 
Published: March 2011

AbstractLow‐molecular‐weight poly(ethylene oxide)‐polyalkane (PEO‐PA) diblock copolymers have been examined between the order‐disorder transition and PEO melting temperature using small‐angle neutron scattering (SANS), differential scanning calorimetry (DSC), and dynamic mechanical spectroscopy (DMS). Crystallization imposes layered ordering with polymer stems oriented perpendicular, or tilted, relative to the microdomain interface, thereby disrupting conventional amorphous microdomain morphologies. This effect can be used to switch the high symmetry bicontinuous ordered G phase to lower symmetry cylinders or lamellae.
Ferroelectric block copolymers
Authors: Brehmer M. , Mao G. , Ober C.K. , Zentel R. 
Published: March 2011

AbstractA block copolymer consisting of polystyrene and a side chain ferroelectric liquid crystalline polymer was synthesized using polymer analogous chemistry on a monodisperse poly(styrene‐b‐isoprene). Composition was adjusted to give lamellar microstructure after addition of the mesogenic side groups. If placed in an LC cell without orientation of domains, no ferroelectric response was observed. After shearing the thin film, presumably due to alignment of lamellae, a bistable ferroelectric switching could be detected.
Hybrid materials made from polymeric betaines and low molar mass salts
Authors: Bonte Nelly , Laschewsky André , Vermylen Valérie 
Published: March 2011

AbstractThe blending of polyzwitterions with low molar mass salts, in particular with salts containing bulky, organic ions is studied. In many cases, homogeneous blends are obtained using stoechiometric amounts of salt, and in selected cases, the amounts of salt which can be admixed is even substantially higher. In contrast to inorganic salts, bulky organic salts are efficient plasticizers. Although the fundamental interaction in such blends is of electrostatic nature, the miscibility depends in a subtle way on specific interactions between particular ionic groups as well as on the molecular structures of polymer and salt.
Induction and stabilization of liquid crystal order in H‐bond complexes containing non‐mesogenic species
Authors: Talroze Raissa V. , Kuptsov Sergei A. , Lebedeva Tamara L. , Shandryuk George A. , Stepina Nina D. 
Published: March 2011

AbstractA new approach to create mesomorphic ordered systems is discussed. It is based on the idea to use noncovalent interactions in the designing of thermotropic structures by modelling lyotropic liquid crystal (LC) when the water interlayer is changed by appropriate solid substances that are able to interact with the polar part of an amphiphilic molecule without any strong change in the intermolecular interactions between the non‐polar “tails”.
Length scales in heterogeneous polymers from solid state NMR
Authors: Spiess H. W. 
Published: March 2011

AbstractNew methods for probing structure and dynamics of heterogeneous polymers by multidimensional nuclear magnetic resonance (NMR) are described. On the molecular level high resolution multiple quantum spectroscopy of solids probes connectivities of different functional groups on length scales below 1 nm. On a mesoscopic scale NMR spin diffusion techniques probe phase separation and interfacial effects in polymer blends and block copolymers. On a macroscopic scale NMR imaging techniques allow to spatially resolve differences in order and mobility in the necking region or in shearbands of deformed polymers. The techniques are illustrated with amorphous polymers, elastomers, and core‐shell systems.
The effects of hydrogen bonding on the liquid crystalline behavior of semiflexible poly(urethaneester)s
Authors: Laus Michele , Angeloni Annino Sante , Francescangeli Oriano , Galli Giancarlo , Chiellini Emo 
Published: March 2011

AbstractThe peculiar liquid crystalline behavior of two poly(urethane‐ester)s TDI‐C6C4 and TDI‐C6C8 is reported. Evidence is provided of the formation of two nematic mesophases, a cybotactic nematic and a conventional nematic mesophase, in TDI‐C6C8 and of one cybotactic nematic mesophase in TDI‐C6C4. IR spectroscopy indicates that different hydrogen bonded and non‐bonded structures occur with varying temperature. The transition from the nematic cybotactic mesophase to the nematic mesophase, or to the isotropic phase, is accompanied by a substantial decrease of the strength of the hydrogen bonds. This is also reflected in the dynamic‐mechanical behavior of these poly(urethane‐ester)s which is similar to the one of slightly crosslinked thermoreversible networks.
Hydrogen bonding as the origin of both liquid crystallinity and polymer formation in some supramolecular materials
Authors: Lee Chien‐Ming , Griffin Anselm C. 
Published: March 2011

AbstractThe use of lateral substitution on the aromatic rings of the diacid component of diacid/bispyridyl AABB supramolecular LC polymers is effective at retarding crystallization presumably by introducing a ‘carbuncle’ along the chain which interferes with the requisite efficient close packing of molecular units. We have examined both one and two chloro groups per ring and have observed a glass transition and fiber formation in the least crystalline complex.
Synthesis of block copolymers by oligomer‐coupling reactions in the bulk: Bisimidazoline/cooh and bisoxazolinone/nh2 reactions
Authors: Fischer Thomas , Lefèbvre Hervé , Fradet Alain 
Published: March 2011

AbstractThe polyaddition reaction of bisimidazolines with α, ω‐dicarboxy polyamide‐12 in the bulk at 200–240°C (oligomer coupling reaction) produces high MW polymers, while degradation reactions were observed with aliphatic polyesters. The chain extension of a α, ω‐dicarboxy polyamide‐polyoxytetramethylene‐polyamide oligomer with 2, 2'‐tetramethylene‐bis(imidazoline) yielded a poly(poly‐ether‐block‐polyamide). 4‐substituted and 4, 4‐disubstituted bis(5(4H)oxazolinones) are efficient coupling agents for amino‐terminated oligomers, allowing the rapid synthesis of copolymers containing polyether and polyamide blocks. The chemistry of these chain‐coupling reactions has been studied by NMR. DSC shows the phase separation between the hard (polyamide) and the soft (polyether) blocks.
Structure development and change in properties of polymers during mechanical degradation
Authors: Xu Xi 
Published: March 2011

AbstractThe effects of ultrasonic irradiation, high speed stirring and vibro‐, jet‐ or pan‐milling on structure and change in properties of polymers were studied in hopes of gaining an innovative route to enhance the processability and properties of polymer materials via polymer stress reaction. A brief survey of ongoing research work done by the author and his colleagues is given in this paper.
Influencing polymer properties by regiospecific complexation
Authors: De Witte Inge C. , Bogdanov Bogdan G. , Goethals Eric J. 
Published: March 2011

AbstractABA block‐copolymers in which the A segments are capable of forming complexes and B is a non‐complexing segment, have been used to prepare polymer materials with properties that can be changed by adding a complexing agent. The complex forming segments were poly(ethylene oxide) (PEO), linear polyethylenimine (LPEI) and poly(N‐tert‐butylethylenimine) (PTBEI).Commercially available liquid ABA block‐copolymers, in which A is PEO and B is poly(propylene oxide), were investigated with high molar mass poly(acrylic acid) (PAA) as the complexing agent for PEO. It was found that the mixtures containing 3 to 7 wt.‐% of PAA, showed a marked shear‐thickening behavior leading eventually to gelation. This was attributed to the transformation of intramolecular polymer complexes, at low shear rates, to intermolecular complexes, at high shear rates, due to the chain stretching of PAA. ABA copolymers in which A is LPEI or PTBEI and B polytetra‐hydrofuran (PTHF), were prepared. Complexation of these copolymers with low molecular weight poly‐acids or PAA in polar and non‐polar solvents as well as in bulk have been investigated. ABA copolymers in which A is PEO and B a PTHF segment were prepared. These block‐copolymers show two melting points: one at appr. 55°C, due to the PEO segments, and one at appr. 30°C due to the PTHF. Upon addition of alkali metal salts such as sodium iodide or sodium thiocyanate, complexes with PEO are formed and as a consequence, the melting point of the PEO segments shifts to appr. 160°C. The complexed materials behave as thermoplastic elastomers up to that temperature.
Functionalization of polyolefins in the melt through reaction with molecules and macromolecules
Authors: Ciardelli Francesco , Aglietto Mauro , Ruggeri Giacomo , Passaglia Elisa , Castelvetro Valter 
Published: March 2011

AbstractFunctionalization of polyolefins with diethyl maleate (DEM) is investigated to improve compatibility with other polar polymers through reactive blending. Functionalization experiments were carried out in the melt with peroxide initiator and mechanical mixers as reactors. The effect of feed composition, reactor type and duration on the functionalization degree, degradation and crosslinking reactions were examined starting with different ethylene polymers. In this way conditions were identified allowing modulation of functionalization with 2‐(diethyl succinate) groups from 0.2 to 2.5% mole, and keep to negligible level undesired by‐reactions such as crosslinking and degradation. The chemical reactivity of these functional groups to form interchain covalent bonds was investigated in case of the reaction of the ester groups on the polyolefin backbone with the amino end group of linear polyamides (in particular PA 6). Evidences of the formation of grafted polymer on the basis of fractionation of the resulting mixture, instrumental analysis and morphological characterization are presented.
Melt memory effects in polymer crystallization
Authors: Alfonso Giovanni C. , Scardigli Paolo 
Published: March 2011

AbstractPolymer melts submitted to local shear flow fields, as well as isotropic solid samples, were treated in the melt at different temperatures and for various duration of time. The effects of thermal history on kinetics and morphological characteristics of subsequent isothermal crystallization was investigated. Results suggest that subcritical pseudocrystalline aggregates, behaving as predetermined athermal nuclei when temperature is brought below melting point, can survive in the melt for long time. Their concentration decays exponentially with a single characteristic relaxation time. For all investigated polymers, temperature dependence of relaxation times can be fitted by an Arrhenius law with high apparent activation energy. Experiments performed with narrow molecular weight fractions of poly(ethylene oxide) suggest that relaxation times relevant to destruction of oriented nucleation precursors are proportional to M1,5.
Modern problems of the theory of macromolecular reactions in polymer blends
Authors: Platé Nicolai , Litmanovich Arkady , Yashin Victor , Kudryavtsev Yaroslav , Govorun Elena 
Published: March 2011

AbstractThe main task of the theory of macromolecular reactions in polymer blends is to describe an evolution of the blend structure under the concerted action of the reaction and interdiffusion. For a polymeranalogous reaction proceeding with autoacceleration in a compatible blend, the task has been solved by methods of linear non‐equilibrium thermodynamics. The set of reaction‐diffusion equations derived permits to describe the blend structure in details, including the parameters characterizing compositional heterogeneity and units' distribution of the reacting chains in any local region of the blend. For incompatible blend of two homopolymers, the competition between a phase separation and the reaction of end‐coupling with a formation of diblock‐copolymer has been considered. The peculiarities of the processes mentioned as well as the actual problems in this field are discussed.
Polymer composites with dual gradient structure
Authors: Choe Chul Rim , Park Min 
Published: March 2011

AbstractFunctionally dual gradient type of carbon fiber reinforced epoxy composites, in which crosslinking density of epoxies and content of carbon fibers are gradually varied through the thickness, were fabricated by using centrifugal force. The spatial variation of fiber content and the crosslinking density change of epoxies were confirmed by checking densities and glass transition temperatures, respectively, along the thickness. The mechanical properties of the polymer composites were also measured.
Polyarylate gas separation membranes
Authors: Paul D. R. , Pixton M. R. 
Published: March 2011

AbstractThe molecular design of polymers for membrane separation of gases is illustrated for the oxygen/nitrogen pair by a series of polyarylates. The use of tetrabromo ring substitutions combined with a fluorene connector group on the bisphenol with or without a t‐butyl group on the isophthalic acid monomer leads to state‐of‐the‐art productivity‐selectivity combinations.
In‐situ complex membrane: Dehydration of pyridine aqueous solution by pervaporation
Authors: Lee Young Moo , Oh Boo‐Keun 
Published: March 2011

AbstractIn this study, we proposed in‐situ complex(ISC) membrane as a new type of PIC. We adapted simple acid/base reaction to invent the ISC membrane and applied to the dehydration of pyridine aqueous solution. ISC forms from the interaction of pyridine in feed and acid moiety in membrane and enhances the water transport through the membrane because of its hydrophilic nature. We compared the separation results by using ISC concept with those of non‐ISC membranes and investigated the effect of the concentration of acid moiety in the membrane on the dehydration of pyridine/water mixture.
Synthesis and thermal modification of n‐substituted functional polymaleimides
Authors: Chung Chan‐Moon , Ahn Kwang‐Duk 
Published: March 2011

AbstractSyntheses, advantageous thermal modification and properties of variously N‐substituted functional polymaleimides are described. Specific thermal properties of the polymers monitored by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) are summarized. The facile modification of the functional polymaleimides by thermal or acid‐catalyzed deprotection offers versatile means in functional transformation and lithographic application of the polymers.
Development of a multideveloping photoresist and its application to make liquid crystal display color filter
Authors: Tseng C. H. , Liu J. M. , Cheng H. C. , Hsieh P. J. 
Published: March 2011

AbstractThis paper reports the fabrication of a single expose multideveloping positive Diazonaphthoquinone (DNQ) /Novolak photoresist capable of simplifying the fabrication process of color filter plates composed of red, green, blue pixels and black matrix. Film thickness retention was measured on multideveloping photoresist(MDPR) containing novolak resins made from various phenolic compounds including cresols, xylenols, trimethylphenol, resorcinol and their copolymers. It was found that there were suitable combinations of phenolic compounds to exhibit appropriate thermal stability, wide process window as well as compatibility to electrodeposition of color films.
Bioconjugate polymer materials that control cell functions
Authors: Imanishi Yukio , Ito Yoshihiro 
Published: March 2011

AbstractSeveral examples of controlling cell functions in serum‐free culture media containing immobilized growth factor are reported. First, the growth and adhesion of cultured STO cells was regulated by insulin conjugated with thermo‐responsive polymers. Second, a photo‐immobilization technique was applied to insulin immobilization, and the photo‐immobilized insulin accelerated the growth of CHO cells. Third, photo‐immobilized EGF affected the differentiation of PC‐12 cells. Finally, a patterned artificial juxtacrine stimulation of CHO cells by insulin covalently immobilized by photo‐lithography is discussed.
Synthesis and characterization of biocompatible and biodegradable polymers
Authors: Sung Yong Kiel , Song Dae Kyung 
Published: March 2011

AbstractNew polyesters were synthesized using Krebs cycle acids. Poly(1, 4‐butanediol dilactate succinate)(PBDS) and poly(1, 4‐butanediol dilactate 2‐acetoxy succinate)(PBDAS) were prepared by the polycondensation of 1, 4‐butanediol dilactate with succinic anhydride and 2‐acetoxy succinic acid, respectively. Poly(1, 4‐butanediol succinate)(PBS) was also synthesized from 1, 4‐butanediol and succinic anhydride. PBS/PBDS and PBS/PBDAS blends were prepared by the method of solvent casting. The effects of crystallization time and temperature onto melting behavior of PBS/PBDS and PBS/PBDAS blends were investigated by differential scanning calorimetry. The compatibility of each blend system was discussed using equilibrium melting point depressions. The biodegradation behavior was studied using PBS, PBDS, and PBDAS as the sole carbon source by Aspergillus niger. The molecular weights of the polymers which were obtained from GPC analysis decreased after degradation in five weeks.