bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis and hydrophobic binding studies on a water‐ soluble tritriptycene
Authors: Webster Owen W. 
Published: March 2011

AbstractThe water soluble tritriptycene 1 was synthesized starting with triptycene trisquinone and anthracene. The hydrophobic binding of substrates to the benzene‐walled cavities in 1 was studied by noting the up‐field shift of substrate protons in the NMR of the substrate in the presence of aqueous 1. Small substrates, negatively charged substrates or substrates larger than the cavities do not bind as strongly as substrates about the same size as the cavities or those bearing a positive charge. Based on differences in AHz'S, the bound substrates position themselves in the cavities so that polar groups are at the water interface.
Recognition and assembly using protein “building blocks”
Authors: McGrath Kevin P. , Kaplan David L. 
Published: March 2011

AbstractA new approach to materials design is presented, utilizing specific recognition and assembly of proteins at the molecular level. The approach exploits the control over polymer chain microstructure afforded by biosynthesis to produce protein‐based materials with precisely defined physical properties. Incorporated into these materials are recognition elements that stringently control the placement and organization of each chain within higher order superstructures. The proteins, designated Recognin A2 through Recognin E2, are recombinant polypeptides designed de novo from both natural consensus sequences and an appreciation of the physical principles governing biological recognition. The synthesis and characterization of the protein recognition elements is briefly described and initial studies on self‐assembly‐recognition patterns using surface plasmon resonance and circular dichroism are presented. A subset of these materials are programmed to spontaneously assembly into complex, multicomponent structures and represent a first step in a rational approach to nanometer‐scale structural design.
Supramolecular architectures from phthalocyanine building blocks
Authors: van Nostrum C. F. , Nolte R.J.M. 
Published: March 2011

AbstractDifferent procedures for preparing columnar stacks and layered structures from phthalocyanine molecules are presented and discussed, including organization of the molecules by one of the following means: (i) with the help of liquid crystallinity, (ii) by using crown ether rings attached to the phthalocyanine core, (iii) by polymerization, and (iv) by Langmuir‐Blodgett film formation.
Helix reversals as bad neighbors to liquid crystal organizations in cholesteric states and thermally reversible gels of poly(ALKYL isocyanates)
Authors: Green Mark M. , Khatri Chetan , Mark Herman F. 
Published: March 2011

AbstractWhile the temperature dependence of the lyotropic cholesteric pitch of the single helical sense poly ((R)‐2,6‐dimethylheptyl isocyanate) is in line with theory, comparable data on this state produced by chiral doping of the lyotropic nematic state of poly(n‐hexyl isocyanate) could suggest an interplay between the supramolecular chirality of the liquid crystal and the dynamic equilibrium of the left and right hand helical blocks in this otherwise racemic polyisocyanate. The exclusion of helix reversals, as undersireable kinks in the liquid crystal organization, could play a role in this effect. Such helix reversal exclusions can also explain the peculiar chiral optical changes associated with the thermally reversible gelation of poly(n‐hexyl isocyanate) copolymers in hydrocarbon solvents. These gels likely arise by entering the broad biphasic region of the Flory phase diagram leading to the formation of liquid crystal aggregates.
Synthesis and physical properties of poly(aryl ether)s containing diphenylacetylene moieties
Authors: Strukelj Marko , Paventi Martino , Hay Allan S. 
Published: March 2011

AbstractPoly(aryl ether)s containing diphenylacetylene moieties in the backbone have been synthesized. When the polymers are heated an exothermic reaction, resulting from reaction of the acetylene units, occurs in the range 380‐ 434°C and the polymers undergo a cross‐linking reaction. Polymers cross‐linked at 340°C exhibit Tg increases from 2°C to complete disappearance of the Tg depending on the concentration of the diphenylacetylene group which has been incorporated into the polymer. In most cases films of the cross‐linked polymers are still flexible and exhibit Young's moduli in the range 1.2‐2.1 GPa at 200°C. The solubility or the amount of swelling of these cross‐linked polymers in solvents depends on the mol % of diphenylacetylene groups incorporated in the polymer backbone. Copolymers have also been synthesized.
Living bimetallic initiators for the preparation of triblock copolymers
Authors: Novak Bruce M. , Deming Timothy J. 
Published: March 2011

AbstractThe compound [(η‐C3H5)Ni(OC(O)CF3)]2 (I), which has been used extensively as a butadiene polymerization catalyst and more recently as an isocyanide polymerization catalyst, has been successfully used in the preparation of polyisocyanide ‐ polybutadiene block copolymers. Since both monomer polymerizations are living, this block copolymer synthesis is highly versatile with respect to polymer segment chain lengths and the types of monomers used. Because non‐reciprocal end‐group activities prevent the preparation of triblock copolymers of the type polyisocyanide‐butadiene‐polyisocyanide, bimetallic initiators possessing two allylnickel moieties linked through a central core have been prepared and used to synthesize these desirable triblock copolymers. These materials have been characterized by using gel‐permeation chromatography, differential scanning calorimetry, 13C NMR and scanning electron microscopy.
Towards a molecular theory of polymer blends
Authors: Freed Karl F. , Dudowicz Jacek 
Published: March 2011

AbstractThe importance of including specific monomer structures, local correlations, and “equation of state effects” into the statistical thermodynamics of polymer blends is accomplished by developing and applying the lattice cluster theory. This new theory provides systematic corrections to Flory‐Huggins theory from local correlations and describes polymers as containing structured monomers that extend over several lattice sites.
Association of macromolecules and its influence on polymer miscibility
Authors: Kuleznev Valery N. 
Published: March 2011

AbstractExperimental data are shown which confirm the existence of increased macromolecules association in a polymer mixture. The increase of association is revealed in the increase of light scattering intensity and the increase of density (local ordering increase). The grown up association degree determines the peculiarities of network formation through cross‐links in the solution of polymer mixtures. Macromolecules associates degrade under mechanical stresses or after addition of slight amounts of substances which are able to interact intensively intermolecularly (solvating) with macromolecules of one of the polymer components in the mixture. Representation of associates formation and degradation in polymer mixture help to explain many experimental data on thermodynamics, structure and properties of polymer mixtures.
Non‐equilibrium thermodynamical description of heterogeneous polymer systems (viii): New concept for understanding brittle‐to‐tough transition in polymer blends
Authors: Wessling Bernhard 
Published: March 2011

AbstractA new model for impact modification in polymer blends is being presented. The new model is derived from the new non‐equilibrium thermodynamical description of heterogeneous polymer systems and is interpreting crazing fracture energy dissipation and fracture mechanism in a new way: on the basis of dissipative structures in polymer blends and their dynamics.
Interface formation between compatible polymers as determined by neutron reflectometry: PMMA and PVC
Authors: Kunz Klaus , Stamm Manfred 
Published: March 2011

AbstractInitial stages of interdiffusion at the interface between two films of poly(methylmethacrylate) (PMMA) and poly(vinyl chloride) (PVC) have been determined by neutron reflectometry. Experiments are performed at temperatures between the glass transition temperatures of the homopolymers. PMMA chains are thus not mobile, but are dissolving in PVC. The growth of the interface width with time follows a power law, which depends on temperature, and the position of the interface moves in the direction of the immobile component. With a PVC film on top, the enrichment of PMMA at the free surface is observed at later times.
Phase diagram and thermal and mechanical properties of isotactic polypropylene/hydrogenated oligo(cyclopentadiene) blends
Authors: Cimmino Sossio , Martuscelli Ezio , Silvestre Clara 
Published: March 2011

AbstractThe system formed by isotactic polypropylene (iPP) and hydrogenated oligo(cyclopentadiene) (HOCP) is investigated in order to study the influence of the composition and thermal history on the morphology, phase structure, miscibility and thermal and mechanical properties of the blends. A phase diagram presenting both the lower and the upper cloud point curves is proposed. It is shown that these blends assume different morphologies and consequently present diverse thermal and dynamic‐mechanical behaviours depending on quenching processes from one‐phase region or two‐phase region. From the analyses of the results of optical microscopy, WAXS, DSC and DMTA techniques it is found that: blend films, quenched from the melt of one‐phase region to room temperature, contain one amorphous phase and iPP in smectic form; moreover they are transparent and possess a reduced permeability to oxygen and aroma; conversely when the samples are quenched from the melt of two‐amorphous phase region there is the formation of two amorphous phases (the iPP‐rich phase and the HOCP‐rich phase) and at room temperature the iPP crystallizes in the monoclinic α form.
Polyolefins ‐ poly(ethylene oxide) blends: Structure and properties
Authors: Kryszewski Marian , Morawiec Jerzy , Pluta Miroslaw , Uznański Pawel 
Published: March 2011

AbstractStructure and properties of polyolefins‐poly(ethylene oxide) (PEO) blends were studied by combination of thermal analysis, light microscopy and fluorescence probe technique. Mixing and preparation conditions influence the calorimetric behavior, changing heat and temperature of melting and crystallinity degree of blended polymers. Values of the static mechanical parameters as well as flow characteristic parameters of the blends are lower for the higher PEO fraction in the samples. Fluorescence investigation of pyrene (changes in the vibrational fine structure) showed a nonhomogeneous distribution of the probe molecules between polyolefin and PEO environment. From these data the partition coefficient between polyolefin and PEO phase can be calculated and correlated with the crystallinity changes of the mixture composition.
Dynamic‐mechanical behaviour in the molten state of iPP/HOCP blends
Authors: Demma Giovanbattista , Acierno Domenico , Martuscelli Ezio 
Published: March 2011

AbstractDynamic‐mechanical data at various temperatures and for different blend compositions are presented for the system iPP/HOCP. The data, in all cases corresponding to the molten state, are relevant not only in view of the processing but especially because they allow some considerations on the blend structure. The data, looked at in different ways (namely the complex viscosity as a function both of frequency and temperature and in the form of Cole‐Cole plots), seem to indicate that the system is always in a single phase. This appears somehow in contrast to some microscopic observations recently reported in literature: the discrepancy may be, however, also due to changes in the miscibility due to the applied stress.
In situ polyolefin alloys
Authors: Cecchin Giuliano 
Published: March 2011

Abstractthrough sequential copolymerization of appropriate ethylene‐propene mixtures into a preformed polypropene, or sligthly modified polypropene matrix (PP), it was possible to achieve and optimize some important property balances of the resulting multiphase copolymers, by finely tuning both the nature of the various phases and their volume and viscosity ratios. Thus, optimum stiffness/impact strength was achieved acting on the stereoregularity and molar mass distribution (MMD) of the polypropene matrix; transparency/impact strength by adjusting heterophase to matrix viscosity or density ratios and, finally, softness/transparency by generating large concentrations of highly amorphous ethylene‐propene bipolymers (EPM).
Blends of the β‐modification of polypropylene
Authors: Varga József , Schulek‐Tóth Ferenc , Mudra István 
Published: March 2011

AbstractPreparation, crystallization and melting characteristics of blends of β‐nucleated isotactic polypropylene with different elastomers and polyethylenes were studied. Blends of β‐polypropylene can be prepared if the polymer additive is amorphous or has negligible α‐nucleating effect during the crystallization of polypropylene.
New polyamide ‐ based blends
Authors: Speroni Franco 
Published: March 2011

AbstractAmong polyamide based blends, PA/PP alloys show interesting technological properties due to low moisture absorption. A model class of PA6/PP homopolymer blends, compatibilized through the addition of PP‐g‐MA is described in the present work; the experimentally obtained morphologies are related to predictive equations for co‐continuity, at given rheological conditions. PP/compatibilizer ratio = 4/1 is found to impart an optimum level of phase dispersion. Moisture absorption, dimensional stability, mechanical properties and morphology are related with blend composition.
Specialties production by an innovative extrusion system
Authors: Addeo A. , Morandi C. , Vezzoli A. 
Published: March 2011

AbstractThe role of reactive extrusion (REX) appears more and more important in the future industry of polymeric materials. This process involves the design of special equipments and sofisticated process monitoring systems to allow complex chemical reactions and diversificated additivation at same time. In this paper, after a description of a specialized equipment designed for REX processing, some examples of experimental studies carried out using this line, are shortly addressed.
Controlled swelling of polymer brushes
Authors: Brochard‐Wyart F. , De Gennes P. G. 
Published: March 2011

AbstractVery long chains with molecular weights up to 600000 can be grafted on a solid surface. We discuss here some specific features of these grafted systems: a) the climbing of a liquid along a vertical plane covered with long grafted polymer chains: because of a minute difference in chemical potential, the brushes can show color variations over an altitude ∼ 1 cm! b) swelling of brushes by elongated solvent molecules: this type of solvent can induce swelling in the isotropic phase, but when they become cooperatively ordered (nematic) we usually expect a collapse of the brush.
Brownian dynamics in strongly scattering porous media ‐ dynamic light scattering with single‐mode matching
Authors: Rička Jaroslav 
Published: March 2011

AbstractBrownian motions in porous media represent a challenging problem not only from a theoretical but also from an experimental point of view. A very powerful technique for the measurement of Brownian motions is Dynamic Light Scattering (DLS). For our problem, however, the classic version of DLS is useless because the porous matrix scatters very strongly and the particles to be measured are completely masked. Sometimes it is possible to suppress the background scattering by matching the refractive indices of the matrix and the confined liquid, but this restricts the applicability to a handful of suitable model systems. We have introduced a new technique which overcomes this difficulty: The keyword issingle‐mode matchingand the idea is to select from the complicated random light field generated by the strongly scattering medium only a single mode so that the contribution from the matrix to the selected mode vanishes because of destructive interference. The first experimental results on the dynamics of latex particles in aqueous suspensions confined in a packing of glass beads are very promising. Their quantitative analysis demonstrates clearly the feasibility of measuring the diffusion coefficient within an opaque strongly scattering porous medium.
Static and dynamic light scattering of a random coil polymer in rodlike polymer solution
Authors: Jamil T. , Russo P. S. , Daly W. H. , Negulescu I. 
Published: March 2011

AbstractWe have studied ternary solutions of rodlike and random coil polymers in a common solvent. In these solutions, the rods scatter weakly, and almost all scattering comes from the coil component. From light scattering measurements, we gained information about the thermodynamic and hydrodynamic properties of the coil in rodlike polymer solutions.
Diffusion, rheology, and flow birefringence in block copolymer liquids near the ordering transition
Authors: Lodge T. P. , Xu X. , Jin X. , Dalvi M. C. 
Published: March 2011

AbstractMeasurements of the diffusion and relaxation of block copolymer chains near the order‐disorder transition (ODT) are reported. Forced Rayleigh scattering has been used to determine the diffusivities parallel and perpendicular to the lamellar planes, for poly(ethylene‐propylene)‐poly(ethylethylene) (PEP‐PEE) melts. The anisotropy is relatively weak (i.e., less than a factor of 4), but increases steadily as temperature is decreased. Rheology and flow birefringence have been employed to examine the conformational dynamics in block copolymer solutions. For PEP‐PEE in squalane, the stress‐optic relation is approximately valid, but the stress‐optic coefficient increases in the ordered state. The location of the ODT is consistent with the dilution approximation. For polystyrene‐polyisoprene (PS‐PI) diblock and triblock copolymers, the stress‐optic relation fails completely. There is evidence that the fluctuation regime (i.e., in the disordered state but near the ODT) may be considerably broader in block copolymer solutions than in melts. Furthermore, the onset of structure in the solution is accompanied by substantial form birefringence. In general, the optical signals are more complicated than the Theological ones, but also much more sensitive to small changes in temperature or concentration.
Dielectric studies on the dynamics of polymer chains in various environments
Authors: Kotaka Tadao , Adachi Keiichiro 
Published: March 2011

AbstractStockmayer's type‐A chain such as cis‐polyisoprene (PI) having dipole moments aligned parallel to the chain contour exhibits slow dielectric response, reflecting fluctuation of the end‐to‐end vector of the chain (dielectric normal modes). This article intends to review our own work on dielectric spectroscopy using PI as a probe for studying dynamics of large scale motion of the probe chain in binary blends with polybutadiene (PB) and in block copolymers with PB or with polystyrene. Through such studies we were able to see the features of polymer chain dynamics in various environments: Rouse‐Zimm‐like dynamics in overlapping‐but‐unentangled regimes, reptation with and without accompanying constraint release, behaviour of a subchain incorporated into block copolymers with miscible segments, and dynamics of polymer brushes in strongly segregating block copolymers in bulk and in solutions.
Synthesis and structure of metal complexes with organic polymers or inorganic supports
Authors: Ciardelli Francesco , Altomare Angelina , Conti Giuseppe , Arribas Guillermo , Mendez Bernardo , Ismayel Alida 
Published: March 2011

AbstractMacromolecular ligands have been widely used in the past two decades with the objective of preparing structurally defined heterogeneous catalysts from soluble organometallic complexes. This activity has been largely reconsidered and focused on few specific systems. In this connection the present paper reviews recent data concerning the preparation of macromolecular metal complexes derived from transition metals which can produce active catalytic complexes for olefin polymerization and oligomerization and comparison is made about the suitability of both organic resins (crosslinked polystyrene) and inorganic materials (silica, alumina and zeolites).
Conduction in polymeric macrocyclic complexes
Authors: Hanack Michael 
Published: March 2011

AbstractBridged macrocyclic transition metal complexes using phthalocyanine and naphthalocyanine macrocycles e.g. [PcM(L)]n with M = Fe, Ru, Co and L = e.g. pyz, dib, tz, SCN−, CN− have been synthesized and their electrical properties studied in detail. Regardless of the bridging ligand stable semiconducting compounds are formed after doping with iodine. Some of these e.g. [PcM(tz)]n, M = Fe, Ru or e.g. [PcM(L)]n, M = Fe, Co; L = CN−, SCN− exhibit good semiconducting properties without additional doping. Substituted phthalocyanines (R4PcM where R = t‐Bu, Et, CH2OC12H25, C5H11‐C8H17) were also synthesized and were found to be more soluble in organic solvents. The characterization of the phthalocyanines prepared were carried out by IR, UV, 1H‐NMR and Mößbauer (Fe) spectroscopy.
Polymer‐supported pd(II) wacker‐type catalysts
Authors: Sherrington David C. , Tang Hui‐Gong 
Published: March 2011

AbstractSeven polymer‐supported Pd(II) catalysts have been prepared employing polymers carrying nitrile (cyanomethyl) ligands. Five of these involve polybenzimidazole backbones, one a polystyrene skeleton and the last a polyacrylonitrile backbone. The supported complexes have been used with CuCl2 co‐catalyst to oxidise dec‐1‐ene primarily to the methylketone under normal Wacker oxidation conditions. In some instances the supported complexes are more active than the (CH3CN)2PdCl2 model. The most active species is a highly rigid ‐ cyanomethylated polybenzimidazole and at least some of these metal centres may be coordinatively unsaturated. This catalyst also displays remarkable thermo‐oxidative stability up to ∼400°C. The effect of solvent, temperature and co‐catalyst ratio have been examined. The polymer‐supported species remain very active at high temperature (∼120°C) and require addition of no hydrochloric acid to avoid irreversible precipitation of Pd(O) species. This is a complete contrast to homogeneous PdCl2 which is rapidly deactivated under similar conditions with copious Pd black formation. Pd(O) complexes immobilised on the polymer seem to be “site isolated” and unable to aggregate. Re‐oxidation therefore remains facile. The polymer‐supported species have been recycled seven times. An initial fall in activity levels after 3 cycles and thereafter remains essentially constant. Appreciable Pd leaching also occurs in the first reaction but is rapidly arrested. After ∼6 cycles Pd loss is only ∼1 ppm per cycle. Following use of CuCl2 co‐catalyst in the first cycle, no additional Cu(II) needs to be added, and sufficient co‐catalyst appears to be carried through with the isolated polymer‐supported Pd(II) species.Starting with alk‐1‐enes isomerisation to the more thermodynamically stable internal alkenes is very much faster than oxidation. Indeed after only a short time no alk‐1‐ene is detectable e.g. by nuclear magnetic resonance analysis. Almost certainly, however, traces of the alk‐1‐ene do exist in equilibrium. Irrespective of whether the starting alkene is oct‐1‐ene, t‐oct‐2‐ene or t‐oct‐4‐ene the same three products are obtained: octan‐2‐one, ‐3‐one and ‐4‐one. In the case of oct‐1‐ene and t‐oct‐2‐ene the composition of the ketone product mixture is very similar, although with t‐oct‐4‐ene a significant increase in the proportion of the 4‐one is observed. The major product in all cases however in the 2‐one. The latter almost certainly arises from rapid oxidation of a small stationary concentration of alk‐1‐ene, with shift of the alkene equilibria maintaining the latter. Direct oxidation of the higher alkenes to the higher ketones occurs more slowly, but contrary to other reports in the literature this is significant.