bluuebunny/crossref_metadata_2025_split huggingface dataset:
Novel structural derivatives of poly‐p‐phenylenevinylene
Authors: Hesemann Peter , Oberski Josef M. , Greiner Andreas 
Published: March 2011

AbstractBlends of oligoarylenevinylenes were prepared with polycarbonate, resp. polystyrene. These blends were investigated by electron microscopy as well as by differential scanning calorimetry (DSC) measurements. Block copolymers with well defined arylenevinylene segments were prepared by polycondensation of OH‐functionalized oligoarylenevinylenes and aliphatic biscarboxylic acid chlorides. Arylenevinylene functionalized polystyrenes were prepared by Pd‐catalyzed coupling reactions.
Living ring opening metathesis polymerization of mesogenic norbornene derivatives
Authors: Pugh Coleen 
Published: March 2011

AbstractA new class of SCLCPs was prepared by polymerizing mesogenic norbornene derivatives using Mo(CHCMe2R)(N‐2,6‐C6H3‐i‐Pr2)(O‐t‐Bu)2 (R = CH3 or Ph). Monomers based on norbornene ring systems were chosen because the rings are highly strained and therefore yield irreversible polymerizations. The Mo‐alkylidene initiators were chosen because they initiate norbornene derivatives relatively fast and quantitatively, and provide stable chain ends which have low reactivity to both the internal double bonds of the polymer backbone and the functional groups present in the monomers. The apparent absence of termination and transfer reactions in ROMP results in polymerizations which appear to be living, and the fast initiation and irreversible chain growth leads to polymers with narrow molecular weight distributions in which the degree of polymerization is controlled by the ratio of monomer to initiator used. The resulting well‐defined polymers were used to determine the most basic structure‐property relationships of this new class of SCLCPs. The thermotropic behavior of both terminally attached and laterally attached SCLCPs based on polynorbornene backbones becomes independent of molecular weight at approximately 25 repeat units. In addition, polydispersity was found to have no effect on the breadth of nematic phase transitions in the terminally attached polymers, with the transition temperature determined simply by the number average degree of polymerization.
Preparation of ordered and crosslinked films from liquid crystalline vinyl ether monomers
Authors: Andersson H. , Sahlén F. , Gedde U. W. , Hult A. 
Published: March 2011

AbstractThermally stable ordered films were prepared by in‐situ photopolymerization of an oriented monomer mixture, consisting of mesogenic monofunctional and bifunctional vinyl ethers. Orientation was achieved by a simple surface treatment, using an unidirectionally rubbed polyimide film. The films restored their orientation when cooled down from temperatures of 200°C. Highly ordered densely crosslinked films have been prepared by polymerization of bifunctional mesogenic vinyl ether monomers. Polymerization from various monomer phases resulted in LC polymer network films with different molecular organizations. It was shown that films with nematic, smectic A and smectic B structures were obtained, the latter having a very high degree of orientation. The films were analyzed with small‐angle X‐ray scattering, polarized light microscopy and infrared‐ dichroism measurements.
Polymers from 4‐(4‐hydroxyphenyl)phthalazin‐1‐one
Authors: Berard Nurit , Paventi Martino , Chan Kwok P. , Hay Allan S. 
Published: March 2011

Abstract2‐(4′‐Hydroxyphenylbenzoyl)benzoic acid is readily available from phenolphthalein by reaction with hydroxylamine. On treatment with hydrazine, 4‐(4‐hydroxyphenyl)phthalazin‐1‐one is formed in high yield. Under conditions conventionally used for the synthesis of poly(aryl ether)s the phthalazinone reacts with 4,4‐difluorobenzophenone or 4,4′‐difluorodiphenyl sulfone to yield high molecular weight linear polymers which are thermooxidatively stable and have Tg's approaching 300°C. The phthalazinone NH groups behave like phenolic OH groups and the resulting polymers contain O‐C and N‐C linkages. Phenyl‐substituted phenolphthaleins have also been synthesized and converted to the corresponding phthalazinone polymers.
Synthesis of polymer networks containing degradable polyacetal segments
Authors: De Clercq R. R. , Trossaert G. G. , Hartmann P. J. , Walraedt S. , Goethals E. J. 
Published: March 2011

AbstractFour different routes for the production of polyacetal containing networks are described : (1) free radical copolymerization of α,ω‐(meth)acrylate terminated polyacetals, (2) hydrosilylation reactions of α,ω‐allyl terminated poly‐ (1,3‐dioxolane) with a multifunctional silane, (3) modification of α,ω‐hydroxy terminated poly(1,3‐dioxepane) through reaction with 3‐isocyanatopropyl‐triethoxysilane and subsequent cross‐linking under influence of H2O and (4) cross‐linking of multifunctional hydroxy‐terminated polyacetals by reaction with a diisocyanate.
Simultaneous hydrosilation and ring‐opening polymerization as a route to novel polymer architectures
Authors: Crivello James V. , Fan Mingxin 
Published: March 2011

AbstractTypical platinum, rhodium and cobalt hydrosilation catalysts have been found to catalyze the ring‐opening polymerization of many different types of heterocyclic monomers. In particular, epoxide monomers undergo especially rapid polymerization with these catalysts. Investigations have shown that in the case of platinum and rhodium catalysts these polymerizations proceed at the surface of the metal colloids by means of a novel cationic mechanism. In contrast, polymerizations with octacarbonyldicobalt take place by a homogeneous cationic mechanism. In all cases, polymerization appears to proceed by the formal attack of a positively charged silicon species on the heteroatom with the formation of a silicon‐oxygen bond. Interesting comb, graft, block and network polymers can be prepared by carrying out simultaneous epoxide ring‐opening and hydrosilation reactions using these catalysts.
The influence of polymer structure and component ratios on blend miscibility
Authors: Cowie John M. G. 
Published: March 2011

AbstractThe mean field, rigid lattice treatment as applied to polymer mixtures has been used to estimate segment‐segment interaction parameters for a wide range of polymers. These parameters incorporate, without distinction, contributions from non‐combinatorial entropy effects, dispersion forces and any specific interactions that operate in the polymer blend. Thus while these parameters can be used to predict successfully the nature of the phases in untested polymer blends, structural effects may also play a role in determining miscibility, and these may have to be assessed individually. Examples of structural effects are described using chlorine‐containing polymers and blends of copolymers with an anhydride ring attached in two different ways to the polymer chain. The extension of binary interaction parameters to the prediction of phase behaviour in complex ternary copolymer blends and the effect on the phase behaviour of changing the component ratios in the blends, is also illustrated.
Effects of polymer‐polymer interactions in multiphase blends or alloys
Authors: Paul D. R. 
Published: March 2011

AbstractThe interaction energy between two polymers determines whether they form a miscible blend or a phase separated one. In the latter, these interactions also determine the nature of the interface between phases which in turn influences stress transfer between the phases in the solid state and morphology generation during formulation. Estimates of polymer‐polymer thermodynamic interactions are used to rationalize the behavior of polycarbonate/ABS materials and a series of polyamides toughened by reactive blending with a functionalized elastomer.
Miscibility of poly(butyl methacrylate‐CO‐methacrylic acid) or poly(styrene‐CO‐methacrylic acid) with poly(styrene‐CO‐4‐vinylpyridine) or poly(butyl methacrylate‐CO‐4‐vinylpyridine)
Authors: Djadoun Said , Karasz Frank E. , Metref Farid 
Published: March 2011

AbstractThe miscibility of blends of copolymers of different compositions of butyl methacrylate‐co‐methacrylic acid or styrene‐co‐methacrylic acid with styrene‐co‐4‐vinylpyridine or butyl methacrylate‐co‐4‐vinylpyridine was studied by differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR) spectroscopy. It was found that these blends were miscible in part as a result of specific favorable interactions between the carboxylic acid and pyridine groups within the polymer chains. Evidence of such interactions was obtained from the single composition‐dependent glass transition temperature and the FTIR results.
Dynamic light scattering by non‐ergodic media
Authors: Pusey P. N. 
Published: March 2011

AbstractThe theory of dynamic light scattering (DLS) by non‐ergodic media, systems such as polymeric gels whose density fluctuations are partially “frozen”, is discussed. We derive the relationship between the time‐averaged time correlation function of the scattered intensity, the quantity measured in a single DLS experiment, and the ensemble‐averaged correlation function of the sample's density fluctuations. The connection between DLS, speckle and the reciprocal‐space structure of the medium is also discussed.
Diffusing‐wave spectroscopy and interferometry
Authors: Pine David J. , Weitz D. A. , Zhu J. X. , Durian D. J. , Yodh A. , Kao M. 
Published: March 2011

AbstractDiffusing‐wave spectroscopy and interferometry, the extensions of dynamic light scattering to materials which exhibit a very high degree of multiple scattering, have been used to measure the early‐time, short length scale motion of Brownian particles. The transition from “ballistic” to “diffusive” motion is observed. In very dilute samples, this transition is described very well by theories which explicitly account for the time‐dependent hydrodynamic interaction between a Brownian particle and the surrounding fluid. For particle volume fractions exceeding a few per cent, the data deviate from the theory for dilute suspensions, but exhibit a remarkable scaling with the suspension viscosity.
Dynamic light scattering by polyelectrolyte solutions
Authors: Schmitz Kenneth S. 
Published: March 2011

AbstractA generalized expression for the apparent diffusion coefficient (Dapp) for macroions as a function of scattering vector (q) is developed. Mathematica®, a system of doing mathematics on a computer, was used to obtain the eigenvalues for a select set of polyion‐electrolyte systems. It is shown that under the conditions of low electrolyte concentration Dapp exhibits a marked q‐dependence. The second part of this communication focuses on the so‐called “ordinary‐extraordinary” transition observed in some polyelectrolyte systems. The characteristic Dapp versus electrolyte profile for this transition is compared with the “splitting” of relaxation times reported for many other polyelectrolyte systems. General problems associated with dynamic light scattering studies on macroion systems are discussed.
Domain growth and wetting in phase‐separating fluid mixtures
Authors: Wiltzius Pierre , Cumming Andrew W. , Shi Bill Q. 
Published: March 2011

AbstractWe present light scattering results from two different fluid mixtures undergoing phase separation next to a glass interface. We observe a characteristic length scale L, which coarsens as a function of time L ∼ t3/2. This growth is faster than any observed previously in bulk samples. The physical process responsible for it is the formation of a wetting layer of one of the two coexisting phases next to the interface. We discuss recent theoretical attempts to explain the fast kinetic mode.
Diffusive relaxation mode in diblock copolymer melts
Authors: Fytas George , Anastasiadis Spiros H. , Semenov Alexander N. 
Published: March 2011

AbstractPhoton correlation spectroscopy in the polarized light scattering geometry can be employed to study the dynamics of composition fluctuations in disordered diblock copolymer melts near the order‐to‐disorder transition. The origin of a diffusive relaxation mode, very recently measured on a series of undiluted copolymers, can be rationalized in terms of composition polydispersity effects rather than relaxation of equilibrium composition configurations of the fluctuation theory.
Luminescence studies of the conformational behaviour of hydrophobically‐modified, water‐soluble polymers
Authors: Ebdon John R. , Lucas David M. , Soutar Ian , Swanson Linda 
Published: March 2011

AbstractA range of hydrophobically‐modified water‐soluble polymers, based upon acrylic acid and methacrylic acid as hydrophilic components, has been studied using various luminescence techniques. Time‐resolved anisotropy measurements, on fluorescently labelled macromolecules, have been used to quantify the extent to which the conformational behaviour of a given polyelectrolyte affects its segmental mobility, and to gauge how such behaviour can be controlled by hydrophobic modification. Room‐temperature stabilized phosphorescence from the labels and/or occluded guests and energy transfer experiments have been used to investigate the nature of the hydrophobic domains formed in these polymers. Hydrophobic modification of polyelectrolytes can be used to enhance the scope of water‐soluble macromolecules as solubilizing media for photochemical and spectroscopic applications.
Brillouin scattering from polymers and gels
Authors: Mallamace Francesco , Micali Norberto , Vasi Cirino , Bansil Rama , Pajevic Sinisha , Sciortino Francesco 
Published: March 2011

AbstractWe report results from Brillouin scattering on highly swollen and crosslinked polymeric gels, i.e. methyl methacrylate (MMA) gels crosslinked with ethylene dimethacrylate (EDMA). The study is performed varying the crosslink amount of the gels from 0 to 6%. The Brillouin spectra are measured at different scattering wavevectors in the angular ranges 90°–150°. Ve also measured the spectra at constant wavevector (90°) changing the scattering volume, in particular we select the size and the positions of the sample scattering volume. The wavevector dependence of the measured quantities confirms that in our system a micro—phase separation phenomenon takes place. In particular, for samples with crosslink contents higher than 3%, Brillouin data (studied in terms of the group velocity) give information about the existence of well defined solid‐ and liquid‐like islands (heterogeneities in the gel structure) with an extent of several hundred Angstroms (as confirmed by elastic scattering data). Furthermore, selecting different spatial positions of the scattering volume (of micrometric sizes) and the overall sizes of the same, and performing the measurements at different times, we are able to observe (for the first time with Brillouin scattering) the non–ergodic behavior typical of this system. We report here preliminary results of such a study.
Macromolecular metal compounds in cancer research: Concepts and synthetic approaches
Authors: Neuse Eberhard W. 
Published: March 2011

AbstractThe anticancer activity of metal compounds has been a topic of major interest in drug research for two decades. Platinum compounds, in particular, includingcisplatin(cis‐diamminedichloroplatinum(II)) and second generation derivatives, have for many years been among the leading drugs administered in clinical cancer therapy, although excessive toxicity, induction of drug resistance, and other formidable, detrimental side effects continue to militate against efficacious utilization and achievement of satisfactory cure rates. Adding to the toxicity problem, most bioactive metal complexes dissolve poorly, if at all, in aqueous media, possess low stability in solution, undergo rapid depletion from central circulation, and often times are prevented from smooth cell entry by molecular charge or polarity. The concept of polymer‐drug conjugation, designed to overcome the pharmacokinetic barriers to satisfactory clinical chemotherapy with present‐day anticancer drugs, is finding increasing acceptance in biomedical research. The concept has been utilized in our laboratory for the purpose of enhancing the effectiveness of metal‐containing carcinostatic agents. In the present communication we demonstrate the practicability of synthesizing platinum‐, iron‐, and tin‐containing polymer conjugates that are biodegradable, dissolve completely in water, and are structurally designed so as to permit release of the active metal compound in the biological environment. Following a brief review of initial results, we discuss selected synthetic approaches and obtained conjugates, in which the metals are bound to polymer‐attached ligands as dichloroplatinum(II), di‐η5‐cyclopentadienyliron, and diorganotin(IV) moieties.
Perconjugated polymer salts a new concept for drug release
Authors: Naarmann Herbert 
Published: March 2011

AbstractPerconjugated polymer salts were prepared from pyrrole and counterions by an electrochemical anodic oxidation process. The counterions, e.g. heparin, penicillin‐monobactam, camphorsulfonic acid, are incorporated in the pyrrole polymers and can be specifically released. The preparation conditions, morphological structure and properties of the polymer salts are described.
Formation, characterization and catalytic activity of PD‐polyheteroarylenes complexes
Authors: Rusanov Alexandre L. , Vol'pin Marc E. , Beliy Alexandre A. , Chigladze Lina G. 
Published: March 2011

AbstractHigh molecular weight polybenzimidazoles, poly[(N‐phenyl)benzimidazoles], polynaphthoylenebenzimidazoles and poly(naphthoylene‐s‐triazoles) were obtained using well‐known polycyclodehydration processes as well as new reactions for their preparation ‐reductive polyheterocyclization and “activated” poly‐cyclocondensation. Treatment of polymers obtained with PdCl2 led to the formation of Pd‐containing polyheteroarylenes complexes. PdII bound to the polymers was reduced to Pd° by treatment with hydrogen or NaBH4. Pd‐polyheteroarylenes complexes obtained may be used as catalysts for the hydrogenation of alkenes and alkynes, for the selective hydrogenation of the triple bonds of unsaturated hydrocarbons in the presence of double bonds etc. Of especially great interest is the utilization of Pd‐polybenzimidazole as catalyst for carbonylation of nitrobenzene and different halogen‐substitited nitrobenzenes in the presence of alcohols leading to the formation of carbamates.
Polyethylene‐bound complexes in carbon monoxide catalytic reactions
Authors: Karakhanov Edward A. , Runova Elena A. , Berezkin Grigori V. , Neimerovets Evgenia B. 
Published: March 2011

AbstractCatalytic reactions of carbon monoxide are investigated in presence of polyethylene‐bound palladium and rhodium complexes and it was shown that such catalysts with temperature‐dependent solubility are applicable for carbonylation of organic halides and hydroformylation of alkenes due to high activity and recoverability.
Synthesis and chemistry of metallo poly(phenylene diacetylenes)
Authors: Neenan Thomas X. , Callstrom Matthew R. , Schueller Olivier J. A. 
Published: March 2011

AbstractWe describe the synthesis and characterization of metallopolymers comprising poly(phenylene diacetylenes) containing platinum and cobalt species coordinated to the triple bonds of the diacetylene moities. Thermal treatment of these polymers as thin films results in their conversion to hetero glassy carbon (HGC). The coordinated metals are retained within the matrices of the glassy carbons as small metallic clusters (∼10‐30 Å for Pt and 50‐1000 Å for cobalt). The platinum doped glassy carbon shows remarkable activity for the reduction of both H+ and O2, a result that has important implications for the development of fuel cell electrodes. At both pH 0 and 7, the platinum Pt‐HGC reduced the overpotential for O2 reduction by ∼800 mV, and resulted in a voltammetric response similar to that of pure platinum.
Photochemical hole burning in macromolecular complexes
Authors: Horie Kazuyuki 
Published: March 2011

AbstractPhotochemical hole burning (PHB) of free‐base porphyrins in host polymers as a site‐selective spectroscopy reveals the existence of vibronic structure in a porphyrin Q‐band peak and low‐energy excitation modes of host polymers. A new mechanism of photon‐gated PHB by two‐color sensitization of photoreactive polymers with a zinc porphyrin is also presented.
Universal aspects of polymer diffusion in random media
Authors: Schäfer Lothar , Ebert Ute 
Published: March 2011

AbstractWe discuss statics and dynamics of an excluded volume polymer moving in a Gaussian distributed random one body potential. Stressing the intimate connection of universality and renormalizability we point out which features can be expected to be universal. We in particular note that universality holds only as long as the excluded volume in some sense dominates over disorder. Whereas universal static properties up to a trivial redefinition of the excluded volume interaction coincide with those found for the standard excluded volume problem, we find highly nontrivial results for universal dynamic quantities. We in particular discuss our recent results on the center of mass motion.
A monte carlo model of network formation by step‐growth: Star‐shaped structures developed at an isolated crosslink site
Authors: Fawcett Allan H. , Hamill Tony , Mcbride Frederick V. , Mee Richard A. W. 
Published: March 2011

AbstractA Monte Carlo lattice model of step growth network formation from systems of divalent and multivalent molecules has been used to investigate the manner in which the latter function as nodes when diluted considerably be the former. Star molecules develop in the simulation, giving nodes that have pendent tails and loops. We show how the number and size of tails and loops is rather insensitive to the valency, f, of the nodes, and examine the distribution functions for the numbers of tails and loops present in the systems at the end of the reaction. Topological considerations created by a high number of valencies that might be expected to enhance molecule size are frustrated by the presence of adjacent segments of chains from developing the full structural potential.
The influence of disorder on a microphase separation of cross‐linked polymer mixtures
Authors: Stepanow S. 
Published: March 2011

AbstractWe generalize the de Gennes' theory of the microphase separation of cross‐linked polymer mixtures to take into account the spatial fluctuations of the elasticity constant c(r) obeying a Poisson distribution. Within a meanfield analysis we found that for weak fluctuations of c(r) the free energy possesses a minimum corresponding to a microphase separation. The size of the domains is enlarged in comparison to the homogeneous case.
Monte carlo simulations of polymer surfaces in a cubic lattice, 1 development of a simulation algorithm and first results
Authors: Olaj Oskar Friedrich , Petrik Thomas , Zifferer Gerhard 
Published: March 2011

AbstractA method is presented which allows to simulate surface properties of a model polymer system (in addition to bulk properties). The decisive parameter which controls the equilibrium concentration of empty sites within the bulk phase as well as the surface properties is the attractive energy operating between nonbonded neighbouring polymer segments. In effect, by varying this parameter between ‐0,5 and ‐1,5 the volume fraction of vacancies in the bulk phase changed from 0,183 to 0,003. All the parameters defined in order to characterize the “roughness” of the surface indicate that the surface gets smoother and smoother with increasing attractive segment‐segment interaction and, accordingly, also with decreasing bulk equilibrium concentration of vacancies.
Polymer brush in mixed solvent. The role of flory interaction parameter χAB of the solvent components
Authors: Birshtein T. M. , Lyatskaya Yu. V. 
Published: March 2011

AbstractThe properties of polymer brush in binary solvent are considered on the base of the mean‐field theory. The role of the interaction parameter χAB of the two components on the brush parameters was specially considered. The mixture of two precipitants was shown to be a good solvent for the polymer brush provided that their interaction parameter χAB is sufficiently great.