bluuebunny/crossref_metadata_2025 huggingface dataset:
Solid state NMR of a polymer composite and of a polymer blend
Authors: Veeman W.S.
Published: March 2011

Although nuclear magnetic resonance may not seem the technique of choice to study interfaces between components in a polymer composite or polymer blend because of its inherent low sensitivity, for certain systems solid state NMR techniques can emphasize the signals from these interfaces. In case of a composite material with an inorganic filler (particles, fibers) cross‐polarization or dipolar dephasing techniques from protons in the organic matrix or in the interphase to nuclei in the filler can be used to selectively observe the nuclei in the surface of the filler. Any changes at the filler surface caused by the presence of the matrix or coupling agent can then be detected. An example of glass reinforced nylon modelcomposites is discussed.

The same techniques can also be used to study interphases in polymer blends when one of the components contains a NMR nucleus that is not present in the other component. As an example the blend poly(vinylidene fluoride)‐poly(methyl methacrylate) is studied and it is shown that such techniques can provide very detailed information about the miscibility at a molecular scale.
Electron microscopy and quantitative polymer morphology
Authors: Bassett D. C.
Published: March 2011

The lamellar nature of semi‐crystalline polymers can now be studied systematically using transmission electron microscopy, especially following permanganic etching. In combination with thermal analysis and selective extraction followed by molecular characterisation, this approach allows the distribution of lamellae, thermal stability and molecular constitution to be mapped in real space. Extension of this methodology has allowed the extraction of individual melt‐crystallized lamellae from bulk polymer. Their study is adding to understanding of fundamental processes of crystal growth.
Effect of phase transitions on the rheology of polymers
Authors: Winter H. Henning
Published: March 2011

Polymeric materials near phase transition conditions exhibit some common features in their linear viscoelastic relaxation patterns. This has been shown by comparing several recent experimental studies of our laboratory. A universal pattern seems to evolve in the case of liquid‐to‐solid transitions such as chemical gelation, crystallization of semi‐crystalline polymers, and nematic to smectic transition in thermotropic liquid crystalline polymers. They all exhibit the self‐similar CW‐spectrum at low frequencies (for ω→0) or long times. Phase separating di‐block copolymers and polymer blends also show this same type of relaxation time spectrum, however, it most likely does not extend to ω→0 and it does not seem to be restricted to the close vicinity of the transition.
Developments in optically nonlinear polymers and devices
Authors: Möhlmann Gustaaf R.
Published: March 2011

Polymeric multilayers including optically nonlinear polymers have been used to make polymeric electro‐optic modulating and switching devices such as phase and intensity modulators and space switches with drive voltages around 10 Volts and 15 dB extinction ratio.
Uncommon methods for spectroscopic analyses of polymers
Authors: Brame Edward G.
Published: March 2011

The commonly used spectroscopic analyses of polymers include infrared (IR), nuclear magnetic resonance (NMR), mass(MS), x‐ray(XR), and the rapidly growing near infrared(NIR). The uncommon methods that are not frequently used include nuclear quadrupole resonance(NQR), electron spin resonance, and combination techniques such as gas chromatography‐infrared, thermal‐infrared, gas chromatography‐mass spectroscopy, and even thermal‐gas chromatography‐infrared or mass spectroscopy. The use of two of these methods (thermal‐infrared(TGA‐IR) and NQR is described. Appropriate examples are shown to point out how useful they can be.
Conformation, ordering and mobility of macromolecules in aromatic polyesters as studied by IR and solid‐state NMR spectroscopy
Authors: Koltsov A. I. , Kapralova V. M. , Khachaturov A. S. , Medvedeva D. A. , Shilov S. V. , Purkina A. V. , Volchek B. Z. , Skorokhodov S. S. , Zuev V. V.
Published: March 2011

Thermotropic main‐chain LC polyesters have been studied with the aid of IR and NMR spectroscopy. Rigid mesogens and mesogens with a possibility of conformational isomerism were examined. The dependence of the order parameters of the mesogens and spacers on the chemical structure of the polymer has been determined. The IR spectroscopy data and the data of the calculation of the possible conformations of the mesogen and the spacer confirm the theoretical predictions about the straightening of macromolecules in the anisotropic melt. Solid‐state 2H NMR spectra show that p‐oxybenzoic rings adjacent to a flexible spacer are more mobile than inner terphthalic rings. In decamethylene spacer the contrary holds true: the mobility of inner methylene groups is more marked than that of the α‐methylene groups bound to the mesogen.
Novel chemistry of β‐lactones anionic polymerization
Authors: Jedliński Zbigniew
Published: March 2011

Some examples of novel chemistry of lactones polymerization are presented. New evidences on β‐lactones polymerization by akali metal alkoxides and, also unusual in organic chemistry, C‐C bond scission in β‐lactones polymerization induced by alkali metal supramolecular complexes are discussed. Preparation of functional polyesters and various block polymers exhibiting “tailored” properties are also described.
Thermodynamics and kinetics of ring‐opening polymerization of cyclic alkylene phosphates
Authors: Penczek Stanislaw , Duda Andrzej , Kaluzynski Krzysztof , Lapienis Grzegorz , Nyk Andrzej , Szymanski Ryszard
Published: March 2011

Polymerization of cyclic compounds containing phosphorus has been used to prepare models of chains of nucleic acids and teichoic acids. Polymers of high molecular weight (M̄n≥105) have been prepared in the past in this laboratory by ring‐opening polymerization. These processes have a number of particular features, related to the low ring strain of the involved monomers (the majority of six‐membered esters are strainless) and to the presence of the labile exocyclic groups. Results of the studies of these polymerizations contributed to the understanding of general phenomena of ring‐opening polymerizations related to these features. In this review paper the thermodynamics of strainless rings is discussed. It is shown that for the same monomer, polymerization can either be exothermic (δHSS<0, δSSS<0) or endothermic, driven by positive change of entropy (δHSS>0, δSSS>0). The presence of the labile exocyclic groups introduce a potential possibility of chain transfer. It is shown that in the cyclic, non‐strained six‐membered monomers kP/ktr is relatively low for cyclic triesters but much higher (≈300) in the polymerization of cyclic amides, since the alcoholate is a better leaving group then the amide group. The importance of these findings for other classes of monomers (cyclic amines, siloxanes, orthoesters) having also labile exocyclic groups is discussed.
Ring opening polymerization of cyclic organosilicon compounds: Recent progress
Authors: Boileau Sylvie
Published: March 2011

A novel initiator, i.e. trimethylsilylmethyllithium has been successfully used for the ring opening polymerization of cyclosiloxanes in toluene, in the presence of the cryptand [211]. Suitable conditions have been found in which monomodal distributions of molecular weights of polysiloxanes are observed by GPC, even in the case of D4 and 1,3,5,7‐tetramethyl‐1,3,5,7‐tetravinyl cyclotetra siloxane (D4Vi) polymerizations. Moreover, kinetics of propagation and of formation of cyclosiloxanes can be followed by 29Si or 13C NMR spectroscopy on living polymer solutions. The rate of propagation of hexaethylcyclotrisiloxane is 120 times lower than that of the corresponding dimethylated analog D3, under the same conditions.
Effect of ammonium polyphosphate on combustion and thermal degradation of aliphatic polyamides
Authors: Levchik S. V. , Costa L. , Camino G.
Published: March 2011

Chain fragments with amide and imide groups are the most abundant degradation products of aliphatic polyamides (APA) which derive from scission of the N‐alkylamide bond (‐CH2‐NH‐). In the case of polyamide 6.6 (PA‐6.6), also carbodiimide structures and methyl chain ends are formed, which derive from scission of ‐CH2‐C(=O)‐ bond. Cyclic compounds can be formed besides chain fragments, depending on the type of APA.

Ammonium polyphosphate (APP) reacts with APA on heating forming phosphoric esters which decompose giving products similar to those obtained from pure APA. APP increases the yield of carbodiimides from PA‐6.6 which trimerise to triazine structures. The fire retardant mechanism of APP is discussed on the basis of the thermal degradation of the mixtures.
Flame‐resistant polynaphthoylenbenzimidazoles
Authors: Rusanov A. L. , Serkov B. B. , Bulycheva E. G. , Kolosova T. N. , Lekae T. V. , Ponomarev I. I. , Matvelashvili N. G.
Published: March 2011

Polynaphthoylenebenzimidazoles, copolynaphthoylenebenzimidazolophenylquinoxalines and copolynaphthoylenebenzimidazolonaphthylimides were obtained by high‐temperature catalytic polycyclocondensation in phenolic solvents. All polymers obtained demonstrate high oxygen index values depending on polymers structure and naphthoylenebenzimidazole rings content in copolymers.
Polymer blends based on epoxy resin and polyphenylene ether as a matrix material for high‐performance composites
Authors: Venderbosch R. W. , Nelissen J.G.L. , Meijer H.E.H. , Lemstra P. J.
Published: March 2011

The application of poly(2,6‐dimethyl‐1,4‐phenylene ether), PPE, as a matrix material for continuous carbon fibre reinforced composites has been studied. Due to the intractable nature of PPE melt impregnation is not feasible and a novel impregnation route, using epoxy resin as a reactive solvent, was developed. The introduction of epoxy resin results in enhanced flow and a reduced processing temperature, enabling the processing of PPE and the preparation of high quality composites. Upon curing, phase separation is initiated and epoxy resin is converted into a second phase. In composites, epoxy resin preferentially accumulates at the polar fibre surface, resulting in an epoxy layer around the fibres, providing a high level of interfacial adhesion. For a high fibre volume fraction (> 50%) this results in the ultimate morphology of epoxy coated fibres in a neat PPE matrix. Due to this unique morphology the composite materials reveal outstanding mechanical properties in terms of interlaminar toughness and impact performance.
Crosslinked polyolefins as matrices for two‐phase materials
Authors: Chodák Ivan , Chorváth Igor
Published: March 2011

This paper gives a review of the results of investigation of the effect of crosslinking on the properties of LDPE/PPa) blends and LDPE filled with particulate silica. Tensile and impact properties, crystallization behaviour, crosslinked portion formation and crack growth rate have been investigated.

Crosslinking results in an increased compatibility of originally incompatible LDPE/PP blends apparently due to an in situ formation of a compatibilizer, leading to improved deformability and better impact resistance. Changes in the morphology as revealed by crystallization behaviour, and the increased number of tie molecules in amorphous region due to crosslinking result in better impact resistance of LDPE/silica mixtures, as well as to the improvement of other properties of two‐phase materials, so as resistance to grack growth.
Synthesis of bisoxazolines and their application as chain extender for poly(ethylene terephthalate)
Authors: Loontjens Ton , Belt Wil , Stanssens Dirk , Weerts Pierre
Published: March 2011

A synthetic method was found to prepare 1,2‐bis‐(2‐oxazolinyl‐2)ethane (BOXE) from succinonitrile and ethanolamine. Succinonitrile is a vicinal dinitrile, which forms with ethanolamine succinimidine. This imidine can be converted in good yield into the corresponding BOXE by heating it while stripping off the excess of ethanolamine.

Bisoxazolines react with the carboxylic endgroups of PET, giving a strong increase in viscosity. The efficiency of this chain extension reaction depends on the structure of the bisoxazoline. BOXE gives a sharp rise in the viscosity of PET after 2.5 min at 270 °C. After prolonged heating the viscosity decreases again, even under the level of the blank. A mechanism is given which describes this unusual behaviour. It is proposed that chain scission takes places in the newly formed esteramide bridge.
Entanglements in amorphous polymer networks
Authors: Erman Burak
Published: March 2011

This paper consists of two parts. In the first part, the strain dependence of entanglements or constraints acting along the contour of a Gaussian chain is derived. The functional form of the elastic free energy resulting from constraints along the chain contour is identical to that obtained in the Flory constrained junction model. In the second part, the effective number of constraints acting along the contour of a chain is discussed. The choice of this number results from postulates imposed by various authors and cannot be derived by rigorous theory. The paper compares the predictions based on these assumptions with experimental data from model networks.
Dynamic light scattering by permanent gels: Partial heterodyne and nonergodic medium methods for data evaluation
Authors: Fang Liqi , Brown Wyn
Published: March 2011

Four relationships between the intensity and field correlation functions have been used in the analysis of the measured intensity correlation function in dynamic light scattering for four different polymer gel samples. The evaluation of diffusion coefficients was performed using inverse Laplace transformation (ILT) and the cumulante method, respectively. The diffusion coefficients derived from the nonergodic medium method are almost the same as those from the partial heterodyne method when ILT is used. ILT can give similar results by all four procedures even when large baselines for the nonergodic medium method exist. The cumulants method leads to incorrect diffusion coefficients from the correlation functions derived using the nonergodic medium method.
Neutron scattering in polymer gels at the theta temperature
Authors: Hecht Anne‐Marie , Horkay Ferenc , Mallam Simon , Geissler Erik
Published: March 2011

Small angle elastic neutron scattering was performed on three polystyrene networks swollen to equilibrium in cyclohexane at the theta temperature. Comparison of the SANS spectra with similar measurements in uncross‐linked solutions reveals that in the intermediate Q region the gels behave like solutions of lower concentration than the equivalent solutions. We assume that the gel spectra are composed of a static component plus a dynamic, or solution‐like part. By a suitable fitting procedure, the former can be estimated, yielding the mean square static concentration fluctuation <Δφ2> generated by cross‐linking contraints in the gel. Independent measurement of the swelling pressure of these gels permits an estimate to be made of the scattering intensity I(Q=0) of the dynamic part of the spectrum. Plausible agreement is found between the macroscopic and microscopic estimations of the osmotic compressibility if allowance is made for the concentration polydispersity in the gels.
Relaxation during stress‐strain cycles of networks in the glass transition range and its description with an onsager approach
Authors: Kraus Volker , Kilian Hanns‐Georg
Published: March 2011

Temperature and strain rate dependence of large cyclic deformations are investigated. The quasi‐static stress‐strain behaviour is described in terms of the van der Waals theory for polymer networks. Within the framework of irreversible thermodynamics, the Gibbs function is extended by hidden variables which represent a set of orthogonal relaxation modes of the Onsager type. These modes are linearly coupled to the quasi static reference state of the network (relaxation mode coupling model). This results in a time dependent expression for the nominal force, where the mode independent relaxation time spectrum plays a dominant role. For high temperatures or low strain rates, the temperature dependence of the spectrum obeys the WLF equation. Approaching the glass transition region, a limitation of the WLF equation is considered. The transition between isothermal and non isothermal deformation is determined.
Determination of the ratio of the shear modulus over the longitudinal modulus for swollen networks
Authors: Zrínyi Miklós , Horkay Ferenc , Rosta János
Published: March 2011

The ratio of the shear modulus over the longitudinal osmotic modulus has been determined by different experimental methods. Osmotic deswelling, swelling kinetics as well as deswelling induced by unidirectional compression were performed. For the experiments chemically cross‐linked poly(vinyl acetate) gels swollen in toluene and acetone (good solvents) and iso‐propyl alcohol (poor solvent) have been used. The results are in agreement with the theoretical predictions.
The influence of interphases on properties of epoxy resin composites
Authors: Kosfeld Robert , Brostow Witold , Hess Michael , Marzi Thomas , Schroeder Ulrich
Published: March 2011

Water sorption was determined and dynamic‐mechanical measurements made on dry and water‐containing systems. Different types of surface treatments of the glass fiber were studied. Immobilization of polymer chains in the interphase is determined by the nature of the curing system, annealing conditions, and surface treatment of glass fibers. Penetrating water can be found at three kinds of locations in the composite; water in the interphase has different properties than water in the polymer matrix and in microvoids. This fact can be used as a microscopic probe in epoxy‐containing composites. Water content depends on the density of polar groups and the density of the network. At higher temperatures water causes crazes, at lower it mainly acts as a plasticizer. Water in crazes does not affect the glass transition temperature Tg, but it decreases (tan δ) and weakens the material. As long as water mainly goes into swelling, energy transfer between the resin and the matrix is not affected. The reinforcement then works as it should. The results demonstrate the importance of interphase properties on the behavior of the composite.
Supramolecular structure and properties of specially designed two‐phase macromolecular systems
Authors: Eisenbach C. D. , Heinemann T. , Ribbe A. , Stadler E.
Published: March 2011

Multiphase polymer systems with special phase structures and properties can be achieved by the proper design of the polymer constitution and the appropriate sample treatment. Multiblock copolymers consisting of molecularly uniform polyurethane segments of various molecularly engineered structures and connected by highly flexible polyether segments have been synthesized. The segregation of the hard segments and the size, shape and perfection of the hard domains can be controlled by the hard segment's architecture in that either extended chain crystallization or chain folding occurs. The same superstructure and properties as of the above multiblock copolymers can be mimicked by specially designed graft copolymers with polyether backbone and polyurethane branches, again uniform and molecularly engineered. This study has shown that the morphology and superstructure of macromolecular systems can be precisely controlled by the molecularly designed chain architecture and the sample history, and is correlated with special material properties.
Effect of headgroup on the supramolecular morphology of diacetylenic aldonamides
Authors: Frankel David A. , O'Brien David F.
Published: March 2011

This report describes the initial characterization of supramolecular morphology of diacetylenic aldonamides where the headgroup has been systematically varied from hexose, pentose, to tetrose. The electron‐dense diacetylenes allow direct electron microscopic imaging of the assembly morphology without the aid of staining reagents. The electron micrographs reveal a dramatic change in supramolecular morphology upon the simple changing the headgroup from D‐galactose to L‐arabinose. Possible reasons for the change in morphology are discussed.
Semi‐interpenetrating polymer networks with controllable morphology ‐ arrest of demixing by thermoreversible gelation
Authors: De Graaf Leontine A. , Möller Martin
Published: March 2011

Semi‐interpenetrating polymer networks with well defined morphologies were obtained using a three‐step process, separating morphology formation and polymerization/crosslinking. Different phase textures were formed when (spinodal) liquid/liquid demixing of a solution of atactic polystyrene in methacrylate monomers was arrested by thermoreversible gelation (vitrification) of the polymer‐rich phase at a desired stage. Subsequent UV‐polymerization of the methacrylate allowed to study the morphology by transmission electron microscopy. Phase diagrams of polymer solutions with low and high viscosities are reported. Depending on the initial solution viscosities and the applied cooling conditions, morphologies both with a dispersed as well with a continuous polystyrene phase could be obtained at PS concentrations already below 10 %. Mechanical measurements indicated only partial demixing in the semi‐IPN's.
Design, preparation, and characterization of hydrogen bonded supramolecular aggregates based on the cyanuric acid‐melamine lattice
Authors: Mathias John P , Simanek Eric E , Seto Christopher T , Whitesides George M
Published: March 2011

Molecular self‐assembly is described as a strategy for synthesizing large hydrogen‐bonded supramolecular aggregates that are based on the planar lattice formed of equimolar portions of cyanuric acid and melamine. The aggregates described in this paper contain four to ten individual molecules, are stabilized by networks of 18 to 54 hydrogen bonds, and have molecular weights in the range 2.7 to 6.5 kDa. Each of these aggregates has been characterized using 1H NMR. spectroscopy, gel permeation chromatography, and vapor pressure osmometry. Physical‐organic chemistry is used to (i) improve our criteria for the design of self‐assembling structures and (ii) develop techniques for characterizing non‐covalently bound aggregates in organic solution.
Supramolecular membranes for optical resolutions and molecular recognitions
Authors: Ogata Naoya
Published: March 2011

Poly(L‐glutamate) having amphiphilic side chains was designed as membrane materials for optical resolution of α ‐amino acids. Solvent‐ cast films of the poly(L‐glutamate) had a self‐ordered structure containing α‐helix of the poly(L‐glutamate). Optical resolutions of various amino acids were carried out through the thin membranes of the amphiphilic poly(L‐glutamate).

Racemic mixtures of Tryptophan were completely separated through the membrane. Mechanism of the optical resolutions was investigated in terms of molecular recognitions of racemic Tryptophan by the ordered structure of the mambrane.
Metal‐directed assembly of coordination oligomers
Authors: Constable Edwin C. , Thompson Alexander M.W. Cargill , Tocher Derek A.
Published: March 2011

Bridging ligands containing two spatially separated 2,2′:6′,2′‐terpyridinyl metal‐binding domains have been prepared and used for the controlled assembly of coordination oligomers incorporating ruthenium(II) and other metal ions. Two such bridging ligands have been structurally characterised. The systematic synthesis of a range of homo‐ and heterometallic polynuclear complexes incorporating these bridging ligands and a variety of terminator 2,2′:6′,2′‐ terpyridines is described.
Precise architecture of 1:1 alternating copolymers between germylenes and p‐benzoquinone derivatives: First clear‐ cut evidence of biradical mechanism in polymerization chemistry
Authors: Kobayashi Shiro , Iwata Satoru , Shoda Shin‐Ichiro
Published: March 2011

Germylenes bearing a bulky amide substituent have been copolymerized with various p‐benzoquinone derivatives without any added catalyst to give novel class of germanium‐containing polymers having a tetravalent germanium unit and a p‐hydroquinone unit alternatingly in the main chain (“oxidation‐reduction alternating copolymerization”). The resulting copolymers have high molecular weight (Mw>5.5×104) and are soluble in common organic solvents. A novel biradical mechanism involving a germyl radical and a semiquinone radical is proposed on the basis of ESR analysis of the propagating polymer end as well as trapping experiments using a disulfide or TEMPO radical.
Modular construction for the programmed assembly of molecular crystals and liquid crystals
Authors: Moore Jeffrey S. , Zhang Jinshan , Wu Ziyan , Venkataraman Dhandapani , Lee Stephen
Published: March 2011

This research aims to develop schemes for the programmed assembly of molecular materials. The underlying premise guiding this work is that structural information stored in the molecular constituents dictates their condensed phase organization (i.e. through the sum of all non‐covalent interactions). The challenge then is to design molecular building blocks that encode this information in a decipherable manner. Our approach has relied on the use of organic nanoarchitectures, which we believe will serve as “modular units” for programmed assembly. Large molecules of well defined constitution and geometry offer the advantage that a high level of information can be incorporated into a single unit. The design and synthesis of nanoscale macrocyclics and macrobicyclics for this purpose has been achieved. Studies on the solution aggregation of the macrocyclics have provided a unique opportunity to glimpse some of the interactions which may influence solid state ordering. These building blocks are being used for the rational design of novel materials such as porous organic crystals and tubular mesophases.
Novel structural derivatives of poly‐p‐phenylenevinylene
Authors: Hesemann Peter , Oberski Josef M. , Greiner Andreas
Published: March 2011

Blends 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

A 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

Thermally 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

2‐(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

Four 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

Typical 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

The 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

The 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

The 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

The 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

Diffusing‐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

A 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

We 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

Photon 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

A 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

We 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

The 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

Perconjugated 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

High 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

Catalytic 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

We 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

Photochemical 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

We 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.
Correlation between glass transition temperatures and entanglement statistics in amorphous polymers
Authors: Bartoš Josef
Published: March 2011

Glass transition temperatures Tg in a series of 24 linear polymers with different chemical structure and high molecular weight beyond entanglement limit are correlated in the framework of freely jointed chain model with the statistical characteristics of chain parts between entanglements.
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

A 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.