bluuebunny/crossref_metadata_2025 huggingface dataset:
Practical methods to control morphology of heterogeneous polymer particles
Authors: Rudin Alfred
Published: March 2011

This review focusses on processes in which emulsion polymerizations are carried out in stages so that previously formed particles are either overcoated in subsequent polymerization stages or engulf the second and later stage polymers. These products are often called “core‐shell” particles. Basically, the most stable state of the final system is the one with the lowest net interfacial energy. In the case of a two‐stage emulsion polymerization there can be three interfacial tensions to consider. Several mutually consistent, effective thermodynamic treatments have been published. At present, they serve primarily to predict when the morphology of multi‐stage polymerization products may not be a simple reflection of the synthesis sequences. It is possible, and frequently desirable, however to produce particle structures that appear at first glance to be thermodynamically forbidden. This is achieved either by changing the surface characteristics of a polymer from those of the bulk material or by employing kinetic factors to anchor energetically unprofitable morphologies. This paper summarizes methods of both types that have been reported to control the texture of structured latex particles in order to produce designed morphologies.
Morphologies of micron‐sized monodispersed composite polymer particles having crosslinked structures produced by seeded polymerizations
Authors: Okubo Masayoshi , Nakagawa Tomoaki , Yamashita Tsuyoshi , Tsuji Morio
Published: March 2011

Three kinds of micron‐sized monodispersed polystyrene (PS)/ poly(styrene ‐ divinylbenzene) composite particles were produced by two kinds of seeded copolymerizations of styrene (S) and divinylbenzene (DVB) (PS seed/ (S+DVB)=2/1, wt. ratio; S/DVB=1/1, molar ratio) in the presence of about 2 μm‐sized monodispersed PS particles, and their morphologies were examined. One was produced by a seeded dispersion copolymerization where almost monomers and initiators exist in an ethanol/water (12.6/4.0, w/w) medium. The others two were produced by seeded copolymerizations with the dynamic swelling method where almost monomers exist in the monomer‐swollen particles using 2, 2'‐azobisisobutyronitrile in monomer‐swollen PS seed particles or using 4, 4'‐azobis (4‐cyanopentanoic acid) in an ethanol/water (7/43, w/w) medium. In the former polymerization, the produced composite particles had a high dense crosslinked shell, whereas in the latter two polymerizations, they did the comparatively homogeneous crosslinked structures.
Characterization of particle morphology by scattering techniques
Authors: Ottewill Ronald H. , Cole Sarah J. , Waters Julian A.
Published: March 2011

A description is given of the application of small angle neutron scattering to examine structural aspects of copolymer particles. Analysis of recent data obtained using a “single shot” polymerisation to prepare polystyrene‐poly (methyl methacrylate) particles shows that these have a core‐shell morphology.
Recent developments in microemulsion copolymerization
Authors: Candau FrançOise
Published: March 2011

Recent results obtained in microemulsion copolymerization are presented. The characteristic features of microemulsions ‐ large interfacial area and great variety of structures ‐ have been used with profit to yield novel materials with interesting morphologies and properties. The examples considered here include the synthesis of i) novel solid porous materials ii) functionalized microlatex particles iii) water‐soluble copolymers with specific properties iv) hydrophilic‐hydrophobic copolymers. The characteristics inherent to each of these syntheses are discussed.
Modelling nucleation and particle growth in emulsion copolymerization in continuous loop reactors
Authors: Abaé Carlos , De La Cal José C. , Asua José M.
Published: March 2011

A mathematical model for emulsion copolymerization in continuous loop reactors is presented. The flow pattern of the loop reactor can be represented by a loop formed by two tubular reactors with axial dispersion. The mathematical model combines this flow model with the physico‐chemical characteristics of the emulsion copolymerization. The outputs of the model are monomer conversion, copolymer composition, particle size distribution and latex viscosity. The model was checked during the redox initiated emulsion copolymerization of vinyl acetate and veova 10 carried out in a completely automated continuous loop reactor.
Kinetics and mechanisms of the seeded emulsion copolymerization of styrene and acrylonitrile
Authors: Nomura Mamoru , Liu Xiang , Mizutani Fumihiko , Sato Syuzaemon , Fujita Kazumi
Published: March 2011

Effects of various operating variables on the kinetic behavior of the seeded emulsion copolymerization of styrene and acrylonitrile and on the monomer concentration in the copolymer particles were examined. Applicability of high‐performance liquid adsorption chromatography to determination of the average composition and composition distribution of the resulting copolymer was also examined.
Main chemical engineering parameters affecting radical polymerization processes in heterogeneous media
Authors: Pla Fernand
Published: March 2011

The main parameters which may affect both reactor performance and polymerization processes in heterogeneous media are described. Viscosity and its influence on heat and mass transfer, residence time distribution in tubular reactor, as well as, influence of agitation on coagulum formation and of monomer feed rate on polymerization rate in semi‐batch processes are examined.
Effect of filler networking on the dynamic mechanical properties of crosslinked polymer solids
Authors: Heinrich Gert , Vilgis Thomas A.
Published: March 2011

The strain amplitude dependence of the viscoelastic properties of eight different carbon blacks dispersed in two different rubbery networks is investigated and evaluated within the Cole‐Cole approach for the complex elastic modulus at fixed temperature and frequency. This approach is based on the Kraus model of strain‐dependent filler agglomeration‐deagglomeration rates. We find a non‐integer universal shape exponent of the Cole‐Cole process that obviously depends only on the surrounding polymer matrix but is independent of the filler grade. The exponent can be related to the fractal dimension of the carbon black surface.
Microstructural evolution in polymerizations of tetrafunctional monomers
Authors: Bowman Christopher N. , Anseth Kristi S.
Published: March 2011

To characterize the network structural evolution during polymerizations of multifunctional monomers and predict the relationship between reaction conditions and polymer structure, a balanced approach between experimental characterization and simulation is used. A novel method for characterizing the free volume distribution and network structure throughout the polymerization is presented. This technique involves the use of photochromic probes that require a certain local, critical volume to isomerize. By incorporating probes that require different isomerization volumes, a distribution of local volume in the network is determined. Since this technique allows in situ monitoring of the volume distribution, the effects of conversion, rates of polymerization, and monomer structure on the free volume distribution can be elucidated. Volume distributions are presented for diethylene glycol dimethacrylate. Information from the photochromic technique is further supported by kinetic gelation model predictions and transmission electron microscopy pictures of the evolving polymer structure.
The bole of vibrational spectroscopy‐microscopy techniques in polymer characterisation
Authors: Chalmers John M. , Everall Neil J.
Published: March 2011

Detailed spectroscopic studies at the sub‐millimetre level of the chemical composition and morphology of materials can provide insights into the constitution, performance and properties of polymeric products. Infrared and Raman microscopy/microprobe spectroscopic techniques are invaluable tools for the spatially‐resolved identification, study and characterisation of polymers, their products and composites. The two vibrational spectroscopy techniques provide both complementary information and attributes to such investigations, which are discussed and exampled in this paper.
In situ vibrational spectroscopy of conducting polymer electrodes
Authors: Neugebauer Helmut
Published: March 2011

The application of in situ Fourier transform infrared spectroscopy for the study of electrochemical redox reactions of conducting polymers is described. The experimental setup of two different methods, external reflection absorption spectroscopy and attenuated total reflection spectroscopy, is shown. The results of spectroelectrochemical investigations of the reactions of polyaniline in different electrolyte solutions are discussed.
Structural polymorphism of crystalline polymers: Electron and atomic force microscopy contributions
Authors: Lotz Bernard
Published: March 2011

The contribution of electron microscopy, electron diffraction and atomic force microscopy to the elucidation of the structure of polymers ‐in particular helical polyolefins‐ is briefly presented. Particular emphasis is put on the elucidation of rather subtle aspects of the structure, such as disorders introduced by packing of up and down, or left and right handed helices in the lattice. The spectroscopic and diffraction informations are evaluated and compared.
The influence of substituents on the orientational behaviour of novel azobenzene side‐chain polyesters
Authors: Zebger Ingo , Kulinna Christian , Siesler Heinz W. , Andruzzi Fulvio , Pedersen Marianne , Ramanujam P. S. , Hvilsted SØRen
Published: March 2011

A series of new mesogenic azobenzene propanediols with nitro, methoxy, cyano and no substituent have been synthesized and their mesomorphic behaviour mapped. The diols are employed in a melt transesterification with diphenyl tetradecanedioate to produce side‐chain polyesters with high molar masses. Diols and polyesters have similar UV‐visible spectra reflecting the acceptor character of the substituent. Polarization FTIR spectroscopy has been used to determine the mesogenic order parameter for the polyesters with different substituents at four laser irradiation wavelengths (413, 458, 488 and 515 nm). Diffraction gratings in thin polyester films have been recorded through polarization holography. Cyano and unsubstituted azobenzene polyesters are shown to exhibit the highest diffraction efficiencies on the order of 13%.
Mechanism of anionic polymerization of methyl methacrylate in the presence of aluminium alkyls
Authors: Schlaad Helmut , Müller Axel H. E.
Published: March 2011

A bimetallic aluminate complex (‘ate’ complex) is regarded to be the active species in the anionic polymerization of MMA in the presence of aluminium alkyls in toluene. The aluminate end group is supposed to be able to coordinate to the penultimate end group of the polymer chain. As a result, the rate of polymerization is significantly slower than for aluminium‐free polymerization. Excess aluminium alkyl (Al/Li > 1) coordinates to the ester carbonyl groups of monomer and polymer, but there is no evidence for an activated monomer mechanism. To a small extent, the polymerization at −78°C is accompanied by side reactions (e.g. formation of vinyl ketones) but nevertheless it has a certain living character.
Cationic photopolymerization of ambifunctional monomers
Authors: Crivello James V. , Bi Daoshen , Lu Yijun
Published: March 2011

Certain metal‐catalyzed hydrosilations have been found to occur in a highly regioselective manner which makes them useful for the preparation of unique classes of ambifunctional monomers. These monomers bear two chemically different functional groups within the same molecule. By selection of the appropriate functional groups it is possible to design monomers in which the functional groups react independently, copolymerize, or polymerize by different mechanisms. This article describes some recent results of the synthesis and polymerization of several novel types of ambifunctional monomers.
Living cationic polymerization of vinyl ethers in the presence of added bases: Recent advances
Authors: Aoshima Sadahito , Kobayashi Eiichi
Published: March 2011

The living cationic polymerization of vinyl ethers was carried out with organoaluminum compounds in the presence of various types of esters and ethers (cyclic and acyclic), to find out the suitable added bases available for the living polymerization. The effects of the basicity and steric hindrance of added bases were investigated in detail. On the basis of these results, a fast living polymerization system was realized. To synthesize water‐soluble polymers such as thermally‐induced phase separating polymers and polyalcohols with well‐defined polymer structure, the living polymerization of various vinyl ethers was examined. The aqueous solution of living poly(vinyl ethers) having oxyethylene units exhibited a quite sensitive (ΔTps=0.3–0.5°C) and reversible phase separation on heating and cooling. The effects of polymer structures (pendant substituent, polymer sequence, molecular weight, and MWD) on the phase separation behavior were investigated. PVA and block copolymers containing PVA units with a narrow MWD were also prepared via living cationic polymerization of vinyl ethers and a deprotection reaction.
From star‐shaped to dendritic poly(ethylene oxide)s: Toward increasingly branched architectures by anionic polymerization
Authors: Six Jean‐Luc , Gnanou Yves
Published: March 2011

Polymers with dendritic structure are a category of macromolecular architectures that has received considerable attention in the last decade. These polymers, also referred to as dendrimers, exhibit a degree of branching equal to unity. Interest in dendrimers whose branching points are linked to each other by generations of macromolecular size is in contrast quite new. This paper describes a new synthetic strategy which allows access to poly(ethylene oxide) (PEO) with dendritic structure. PEO dendrimers with different degree of compactness have been synthesized upon modifying the size of successive generations.
Ring‐opening metathesis polymerization of ω‐norbornenyl polystyrene macromonomers and characterization of the corresponding structures
Authors: Breunig S. , Héroguez V. , Gnanou Y. , Fontanille M.
Published: March 2011

ω‐Norbornenyl polystyrene (PS) macromonomers whose molar masses range from 2700 to 11000 g/mole have been polymerized under living conditions by ring‐opening metathesis, with a Schrock complex as initiator. The samples obtained have been characterized by a multiangle laser light scattering (MLLS) detector connected to the outlet of a size exclusion chromatography (SEC) instrument. The experimental values of the degree of polymerization (D̄Pn) lie in close agreement with the expected ones. The compactness of the various branched species formed, which covers a wide range of segment densities (ρS), is found to depend on two factors that are their degree of polymerization and the size of the initial macromonomer. The ratio (g) of the mean‐square radii gyration (<R2b) of polymacromonomers to those (<R21) of linear PS homologues of same molar mass was also determined. Plotting the variation of g vs. the D̄Pn's of polymacromonomers gives an idea of the conformation adopted by these branched structures.
New developments in bond‐forming initiation: Lewis acids accelerate spontaneous initiation of copolymerizations of olefins and dienes
Authors: Hall H.K. , Padias Anne Buyle , Srisiri Warunee , Mikhael Michael G. , Wang Hua , Chu Guobei
Published: March 2011

Lewis acids have long been known to influence the free radical propagation of donor‐acceptor olefin monomer pairs, changing random copolymers into strictly alternating ones, by complexing to the lone pair electrons of the acceptor monomer, and enhancing its electron‐poor character. This work reports that this same interaction enhances the rates of the spontaneous initiation in these systems. In agreement with earlier literature, we found that styrene‐acrylonitrile copolymerizations proceed readily in the presence of ZnCl2 at 40° where no copolymerization occurs in the absence of the Lewis acid. p‐Methoxystyrene and isobutyl vinyl ether with AN gave more complicated results, due to competitive complexation of oxygen lone pairs with ZnCl2. Reaction of more electrophilic olefins with these donor monomers gave steadily increasing rates and a shift in product from spontaneous copolymer to inverse Diels‐Alder adduct (in the case of ester substituents) to cyclobutane. As for substituted diene monomers as the donor component, reactions of isoprene and 2,3‐dimethylbutadiene with AN are accelerated in the presence of ZnCl2 and the Lewis acid affects the competition between the [4+2] cycloaddition and the copolymerization. All of these results are interpreted in the context of formation of Lewis‐acid complexed initiating diradicals by bond‐formation.
A new understanding of the co‐catalytic activity of alumoxanes: The opening of a black box!
Authors: Barron Andrew R.
Published: March 2011

The isolation of non‐fluxional alumoxane compounds, [(tBu)2Al{OAl(tBu)2}]2 and [(tBu)AlO]n (n = 6, 7, 8, 9), has allowed for an investigation of the mode of activity observed for alumoxanes as co‐catalysts for the zirconocene polymerization of olefins. [(tBu)2Al{OAl(tBu)2}]2, which contains two three‐coordinate aluminum centers, shows no reaction with Cp2ZrMe2, and no catalytic activity towards ethylene polymerization. In contrast, the closed cage compound [(tBu)AlO]6 reacts reversibly to give the ion pair complex, [Cp2ZrMe][(rBu)6Al6O6Me], which is active as a catalyst for the polymerization of ethylene. Polymerization is also observed for mixtures of Cp2ZrMe2 with [(tBu)AlO]n (n = 7, 9). A new concept, “latent Lewis acidity”, is proposed to account for the reactivity of the cage alumoxanes, [(tBu)AlO]n.
Stereospecific polymerization with metallocenes: Macromolecular design via catalysis
Authors: Waymouth Robert M. , Coates Geoff , Mogstad Anne‐Lise , Stein Kevin , Fischer David , Borkowsky Sam
Published: March 2011

Forty years after Natta's discoveries of stereospecific olefin polymerization with Ziegler catalysts, new catalysts are causing a renaissance in stereospecific olefin polymerization. Metallocene Ziegler‐Natta catalysts are unprecedented in their ability to polymerize α‐olefins to a variety of polymer microstructures.1 Isotactic, syndiotactic, atactic and stereoblock poly(α‐olefins) have been produced using catalysts derived from group 4 metallocene catalyst precursors.
New polyimides using hydrazine as the diamine
Authors: Ghassemi Hossein , Hay Allan S.
Published: March 2011

Hydrazine reacts with 1, 8‐naphthalic anhydride to give, exclusively, the N‐aminoimide which reacts further with cyclic anhydrides to yield stable bisimides containing an N‐N linkage. Various bisanhydrides which contain the naphthalic anhydride moiety have been converted to the corresponding bis‐N‐aminoimides from which high molecular weight polyimides have been synthesized. The polyimides have very high glass transition temperatures but remain soluble. Polyimides derived from 3, 4, 9, 10‐perylene tetracarboxylic dianhydride are intensely red in color and are fluorescent.
Transition metal catalyzed cationic polymerizations
Authors: Crivello James V. , Fan Mingxin
Published: March 2011

Certain complexes of platinum, rhodium, iridium and cobalt are capable of initiating cationic vinyl and ring‐opening polymerizations in the presence of a Si‐H containing cocatalyst. An investigation has shown that two distinctly different mechanisms are involved, however, in both cases cationic polymerization can be explained by the formal attack of an electrophilic silicon species on the monomers. Since the transition metal complexes listed above also are catalysts for hydrosilation reactions, it is possible to carry out simultaneous cationic polymerizations and hydrosilation reactions to prepare novel and interesting polymers and oligomers.
Genealogically directed syntheses (polymerizations): Direct evidence by electrospray mass spectroscopy
Authors: Dvornic Petar R. , Tomalia Donald A.
Published: March 2011

From a synthetic perspective, divergent dendrimer syntheses are often presented as idealized hyperbranched growth processes leading to perfect dendritic structures. Experimentally it has been found that in addition to ideal structures, varying amounts of structural errors are produced at each growth stage (generation). These defects (mutants) are created as a function of processing conditions and generation specific steric effects. This investigation focused on the divergent synthesis of Starburstr̀ polyamidoamine dendrimers** and the use of electrospray mass spectroscopy for appraising ideal structure/defect ratios as a function of generation. With this methodology, initial defect types and so called “defect propagation chains” have been identified and characterized. These hyperbranched mutation (defect) patterns provide ample evidence for the “genealogically directed” character of this divergent polymerization strategy.
New materials with novel topologies. Synthesis and characterisation of telomers and polymers with ribbon topology
Authors: Feast W. James , Mitra Manju , Davies Frank P.
Published: March 2011

The five, seven and nine ring analogues of thianthrene have been made as model compounds for ribbon polymers based on the structural motif shown below.

The smaller molecules are soluble and readily characterised but the nine ring model compound and polymers based on this structural motif are insoluble and intractable. Analogues of the model compounds and polymers which carry decyl substituents are soluble upto species having about seventy rings.
Cylindrically shaped dendritic structures
Authors: Schlüter Arnulf‐Dieter , Claussen Wilhelm , Freudenberger Rainer
Published: March 2011

Initial steps toward the grafting of functionalized rodlike polymers with Fréchet‐type dendritic fragments of the first two generations are described.
The protein folding problem: Searching conformations of compact chain molecule
Authors: Dill Ken A. , Chan Hue Sun , Yue Kai
Published: March 2011

A simple model of self‐avoiding chains of specific‐sequence copolymers of H (hydrophobic) and P (polar) monomers on lattices gives many of the properties of proteins, including their tertiary structural symmetries.
Recent advances in the design of polymers for contact lenses
Authors: Friends Gary D. , Kunzler Jay F. , Ozark Richard M.
Published: March 2011

Three approaches for the design of polymers for extended wear contact lenses possessing high oxygen permeability are described. These approaches include the design of high strength, high water content hydrogels, the design of low water content fluorosilicone based materials and the design of hydrogels based on methacrylate end capped hydrophilic side chain siloxanes.
Biorecognizable polymers: Structure‐properties relationship
Authors: Kopeček J. , Kopečková P. , Omelyanenko V. G. , Rathi R. C.
Published: March 2011

The biocompatibility of polymers depends on their chemical composition, as well as physical and physico‐chemical structure. However, biocompatibility is not an intrinsic polymer property since it relates to a particular localization of the polymer in the living organism. Any foreign macromolecule may be recognized by the living organism as “non‐self”. The degree of recognition can be altered by modification of the structure of macromolecules or biomaterial surfaces. Modification of biomacromolecules (e.g., enzymes1) or biomaterial surfaces with hydrophilic polymers, e.g., poly(ethylene oxide2) or other semitelechelic hydrophilic macromolecules3 has been shown to minimize biorecognition. On the other hand, to achieve specific recognition by cell receptors and/or antigens, complementary structures have to be incorporated as a part of the polymer structure4, 5. The biorecognition of fluorescently labeled N‐(2‐hydroxypropyl)‐methacrylamide copolymers containing side‐chains terminated in acylated galactosamine by Hep G2 cells on the cellular and subcellular levels can be visualized by confocal fluorescence microscopy. The recognition of modified water soluble macromolecules strongly depends on their solution properties6. Incorporation of stimuli sensitive moieties into copolymer side‐chains permits to control recognition by external stimuli, e.g., irradiation7, 8, resulting in the change of the copolymer conformation. On the other hand, the biorecognition of unsoluble (crosslinked) copolymers depends mainly on their surface structure. The rationale for the structure modification of synthetic copolymers to regulate biorecognition will be reviewed. The principles will be described for the interaction of synthetic polymers with enzymes9, cell surface receptors and/or antigens10, 11, lectins of the gastrointestinal tract12, 13, and immobilized lectins14.
Homogeneous and heterogeneous free radical polymerizations in environmentally responsible supercritical carbon dioxide
Authors: Desimone Joseph
Published: March 2011

Fluoropolymers are used in many technologically demanding applications because of their balance of high‐performance properties. A significant impediment to the synthesis of variants of commercially available amorphous fluoropolymers is their general insolubility in most solvents except chlorofluorocarbons (CFCs). The environmental concerns about CFCs can be circumvented by preparing these technologically important materials in supercritical fluids (SCFs). The homogeneous solution homo‐ and copolymerization of highly fluorinated acrylic, styrenic and olefinic monomers in supercritical carbon dioxide using free radical methods will be discussed [Science, 257, 945 (1992)]. Detailed decomposition rates and efficiency factors will be presented for azobisisobutyronitrile (AIBN) in supercritical carbon dioxide and will be compared to conventional liquid solvents [Macromolecules, 26, 2663 (1993)]. Additionally, viscosities of polymer solutions in supercritical CO2 have been measured using a high pressure, falling cylinder viscometer. The results show that the polymer solution viscosities in supercritical CO2 are an order of magnitude lower than with the same polymers in conventional organic solvents.

The results from these homogeneous solution polymerization studies has allowed us to also consider heterogeneous polymerizations in a carbon dioxide continuous phase. Conventional emulsion polymerizations of unsaturated monomers are performed in either aqueous or organic dispersion media with addition of surface active agents (surfactants) to stabilize the colloidal dispersion that forms. With free radical initiators that are preferentially soluble in the continuous phase, high rates of polymerization and high molar mass polymers can be obtained simultaneously. Herein we describe an environmentally responsible alternative to aqueous and organic dispersing media for emulsion polymerizations which utilizes supercritical carbon dioxide, in conjunction with molecularly engineered free radical initiators and amphiphilic molecules that are specifically designed to be interfacially active in CO2. Conventional lipophilic monomers, exemplified by methyl methacrylate and styrene, can be polymerized heterogeneously using a fluorinated azo‐initiator in supercritical CO2 in the presence of added surfactant to form stable emulsions that result in submicron size particles. Detailed surfactant and initiator syntheses and phase behavior will also be discussed.
New tools for analysing degradation
Authors: Albertsson Ann‐Christine , Karlsson Sigbritt
Published: March 2011

New tools for analysing degradability are presented. The degradation product patterns and morphology changes are proved to be means to differentiate on the one hand physical/chemical (abiotic) and on the other hand biological (biotic) ageing of polymers. In the biotic environment an assimilation of carboxylic acids occurs and a series of longer n‐alkanes (C21–C26) is present. In the abiotic samples carboxylic acids are identified but no n‐alkanes. This is in agreement with the biodegradation mechanism of LDPE proposed by us 1987. Morphology changes as manifested by crystallinity (wc) and lamella thickness (l) revealed a slow decrease of wc and (l) in biotically aged samples while the corresponding abiotically aged ones show constant or increasing values. Chromatography of low molecular weight compounds and x‐ray diffraction analysis of crystallinity and lamellae thickness creates an opportunity for a deeper insight into the degradation mechanisms.
Coils, globules and single chain glasses
Authors: Napper Donald H.
Published: March 2011

The cyclic coil‐globule‐coil transitions for poly(N‐isopropylacrylamide) tethered to an interface exhibit unexpected phenomena. Two, not the predicted single, coil‐to‐globule transitions can be observed: the one that is predicted occurs in worse than θ‐solvents whereas the other is observed in better than θ‐solvents. The latter phenomenon appears to be associated with the the formation of n‐clusters, first postulated by de Gennes. The chains in their globular form were found to undergo an entropy driven entanglement process that prevents reversible swelling in the globule‐to‐coil transition and leads to hysteresis in the layer thickness. Single chain glasses of polystyrene prepared by microemulsion polymerisation display physical properties different from those of multichain glasses including a higher conformational temperature, larger free volume and a predominantly exothermic rather than an endothermic DSC scan near Tg. These observations have been attributed to the occurrence of cohesional entanglements.
Scattering from polymer films and its application to optical properties of blends and display devices
Authors: Stein Richard S. , Srinivasarao Mohan , Müller Jörg
Published: March 2011

The application of the technique of observing the light scattering from solid polymers for the study of amorphous phase separation, spherulitic crystallization, phase separation in crystalline polymers, and coarsening of liquid crystal polymers is reviewed. The effect of shear and electrical and magnetic fields on liquid crystal orientation is discussed and its application for constructing light control and display devices is considered.
Two‐dimensional NMR studies of molecular dynamics in heterogeneous polymers
Authors: Spiess H. W.
Published: March 2011

Advanced two‐dimensional solid‐state NMR techniques making use of 1H spin diffusion and high resolution 13C detection are powerful tools for the non‐destructive investigation of polymer morphologies and domain sizes. The spin diffusion coefficients needed for quantitative analysis have been calibrated for both rigid and mobile polymers by combining NMR, X‐ray scattering and electron microscopic measurements on diblock copolymers of known morphologies. It turns out that NMR is particularly sensitive to detect small domains in the range of 2–10 nm, and to residual heterogeneities in larger domains, reflected in changes of chain mobility. Last, but not least, NMR is a sensitive tool for characterizing interfacial regions.

The techniques will be introduced and demonstrated on various block copolymers including core shell systems, polymer blends and layered systems of rigid rods and flexible side chains. There, the side chain mobility is directly related to the chain conformation and density modulations within the layers.
Effect of local dynamics on model epoxy resins
Authors: Monnerie L. , Halary J. L. , Lauprêtre F.
Published: March 2011

A series of epoxy resins has been prepared with different chain stiffness either in the diepoxide residue or in the diamine crosslinker (1). Furthermore, the crosslink density has been changed by incorporating either monoamine or secondary diamine as a chain extender, but in each system the stoichiometric ratio was maintained (1).

Viscoelastic measurements were performed over a wide range of frequencies with the aim of determining the main characteristics associated with the Tg and β relaxation processes (2, 3). In a complementary way, high resolution solid state 13C NMR measurements were carried out to determine the mobilities of the different aliphatic carbons in the epoxy moieties (4).

The effects of the chemical structure and of the crosslink density on the mobility of the different groups and the consequences on the Tg values, the amplitude of the β transition and the modulus of the resins are analyzed (5).
Effect of flow on polymer‐polymer miscibility
Authors: Fernandez Maria L. , Higgins Julia S.
Published: March 2011

The effect of shear flow on the phase behaviour of partially miscible blends exhibiting a lower critical solution temperature behaviour has been investigated. Miscibility limits were detected, with and without the application of flow, as changes from optical clarity to turbidity using light scattering and as the appearance of double glass transition temperatures. Light scattering data were collected on a rheo‐optical device that was designed to monitor phase changes in polymer blends undergoing shear flow between parallel glass plates in a temperature controlled environment. Glass transition temperatures of some quenched sheared blends were measured using a differential scanning calorimeter in order to confirm the conclusions from the light scattering data. It was found that shear induced demixing and shear induced mixing may be observed within the same blend depending on the magnitude of the applied flow. Miscibility gaps and closed miscibility loops may appear in the phase diagrams. At certain temperatures and shear rates unusual scattering patterns were observed and these were associated with a “ripple” morphology when directly viewed through the microscope.
Creep and yield behaviour of polyethylene
Authors: Ward Ian M.
Published: March 2011

Extensive studies of the creep and recovery behaviour of oriented polyethylene have been undertaken because of the potential engineering applications of high modulus polyethylene fibres and large section oriented materials made by the Leeds die‐drawing process. Two primary requirements are a valid protocol for the practical assessment of the creep behaviour and an adequate formal representation which can provide the basis for a physical interpretation of the creep processes in terms of the structure of the oriented materials.

The practical requirements of improved creep performance lead to examination of the effects of molecular weight and copolymerisation on creep and recovery, together with studies of the effects of radiation cross‐linking either before or after drawing. A particular new feature has been the development of a process for cross‐linking in acetylene, where it has been shown that diene bridge crosslinks are produced with very little chain scission.

The protocol adopted for assessing creep behaviour is to construct creep strain rate/strain (Sherby‐Dorn) plots which, for highly oriented fibres, show constant strain rates after an initial period. These equilibrium strain rates can be modelled by two thermally activated processes acting in parallel.

In recent research these studies have been extended to fibres of lower draw ratio and to isotropic polyethylene. It has been possible to establish links between creep and yield behaviour, and to show that slow crack propagation can be understood in terms of a combination of yield and creep to failure.
New polymer systems exhibiting microphase separation transition with the formation of nano‐microstructures
Authors: Khokhlov Alexei R.
Published: March 2011

The concept of microphase separation was up to now widely applied mainly to the conformational transitions in block‐copolymer solutions and melts. However, recently it became obvious that this concept has a much more general meaning. It was shown that microphase separation transition can be observed in random copolymers, interpenetrating polymer networks, polyelectrolyte mixtures, poor solvent polyelectrolyte solutions, ionomer solutions and melts, polymer blends and solutions with nonlocal entropy of mixing. In all these examples the emerging microdomain structures correspond to the nanometer scale, therefore the study of these effects can lead to the new ways of obtaining polymer materials with controlled nano‐microstructure.

In this presentation the review of our recent findings on microphase separation in some of the above‐mentioned systems will be presented.

1. The problem of microphase separation in the systems containing weakly charged polyelectrolytes (polyelectrolyte mixtures and poor solvent polyelectrolyte solutions) will be considered. From the methodic point of view, it will be shown that this problem can be solved by direct minimization of the free energy, without the use of “weak segregation” or “strong segregation” assumptions which are common in the theory of block‐copolymers. The final phase diagrams exhibit wide macroscopic phase separation regions, which is their main difference from the corresponding phase diagrams for block‐copolymer systems. The formation of microdomains is thus coupled with macroscopic phase separation: in most of the cases microdomain structure is formed in one of the coexisting phases after macroscopic phase separation takes place [1] ‐ [2].

2. The formation of the multiplet structure in ionomer melts and solutions can be also considered as the microphase separation in the random copolymer system with the formation of the “micelles” (or clusters) of ionic links. The parallels with micelle formation in block‐copolymer systems can be established if one considers a new “superstrong segregation regime” for block‐copolymer microstructures. This regime can be indeed observed for diblock copolymers with one ionomeric and one neutral block [3].

3. The microphase separation transition in ordinary polymer blends and solutions is also possible. The conditions for this effect are: (i) significant entropic contribution to polymer/polymer or polymer/solvent miscibility, (ii) the nonlocal character of this contribution with a high value of the nonlocality radius. It is argued that one can expect that the entropy nonlocality radius increases in the vicinity of the glass transition for the blend or polymer solutions (in the latter case solvent molecules act like “poor solvent plasticisers”). Computer simulation data supporting the theoretical prediction of microphase separation transition in these systems will be presented [4] ‐ [5].
Precursor method for polymeric LB films
Authors: Kakimoto Masa‐Aki , Imai Yoshio
Published: March 2011

First, the general concept of the “Precursor Method” for the preparation of polymeric Langmuir‐Blodgett (LB) films that possess no long alkyl chain between film layers, and the preparation of polybenzothiazole 7 LB film are described. The preparation of 7 LB film was carried out by the same procedure as that used to make polyimide LB films via precursor LB films of polyamides that contain β‐carboxyethylthio alkylamine salts 6. Precursor 6 LB film had a Y type structure with monolayer thickness of 2.8 nm, while polybenzothiazole 7 LB film had 0.34 nm. The nonlinear susceptibility χ(3) of polybenzothiazole 7 LB film in parallel to the dipping direction was 3.8 × 10−11 esu, whereas the susceptibility in the perpendicular direction was about one fifth of that of the parallel direction.
Thermoreversible gelation of a polysaccharide with immunological activity: Rheology and dynamic light scattering
Authors: Fuchs Tania , Richtering Walter , Burchard Walther
Published: March 2011

The β — 1.3/1.6 glucan schizophyllan is known to suppress tumor growth. Two different schizophyllan samples have been characterized by static and dynamic light scattering in dilute solution of 0.01M NaOH and dimethyl sulfoxide (DMSO). A thermoreversible, optically transparent gel of schizophyllan was obtained on addition of sorbitol to aqueous solution, and the gelation process was followed by low amplitude oscillatory shear and dynamic light scattering (DLS). Power law behavior of storage modulus G'(ω) and loss modulus G”(ω) with the exponent n=0.5 was found at the gel temperature. In the same temperature range intensity time correlation functions (TCF) were measured and the electric field TCFs were calculated, taking into account the heterodyne contributions. The occurrence of two motions gave evidence for inhomogeneities in the gel. The results of the slow motion from DLS agreed surprisingly well with those, estimated by oscillatory rheology. The viscoelastic properties and the influence of sorbitol and schizophyllan concentrations were investigated regarding the pharmaceutical application in cancer therapy.
Structural characteristics of polysaccharide‐based thermotropic liquid crystals
Authors: Fukuda Takeshi , Tsujii Yoshinobu , Miyamoto Takeaki
Published: March 2011

Main mesomorphic properties of cellulose and cello‐ and chito‐oligosaccharide derivatives are overviewed, and their structuring principles are briefly discussed with some new analyses incorporated.
Acrylic thermoplastic elastomers and comb‐shaped poly(methyl methacrylate) via the macromonomer technique
Authors: Radke Wolfgang , Roos Sebastian , Stein Helga M. , Müller Axel H. E.
Published: March 2011

Comb‐shaped poly(methyl methacrylate) (PMMA) and poly(butyl acrylate) (PnBuA) grafted with PMMA were prepared by radical copolymerization of ω‐methacryloyl‐PMMA with MMA and nBuA, respectively. The comb‐shaped PMMA is characterized with respect to radius of gyration by using gel permeation chromatography equipped with a multi‐angle laser light scattering detector. The radical copolymerization of the macromonomer with nBuA in toluene follows complex kinetics. The dependence of the relative reactivity of the macromonomer on absolute concentration and on the ratio of comonomers may be explained by preferential solvation of comonomers by segments of their own kind (“bootstrap effect”) or even micelle formation. However, there is no clear evidence for the formation of micelles in toluene. In contrast, NMR studies show micelle formation in the preferential solvent dimethyl sulfoxide. The graft copolymers are transparent thermoplastic elastomers. Phase separation is demonstrated by differential scanning calorimetry and morphological studies.
A new oral microsphere drug delivery system
Authors: Ottenbrite Raphael M. , Zhao Ruifeng , Milsteln Sam
Published: March 2011

A new oral proteinoid microsphere drug delivery system is discussed with respect to its unique dependence on pH. Extensive evidence indicate that this technique not only can be used to deliver the protein and polar macromolecular drugs which are currently administered via injection, but also can be used to administer antigens and vaccines. Future work has been proposed to study the physical interaction of specific drugs with specifically designed oligopeptides structures.
Nonthrombogenic polymers ‐ designs and evaluation
Authors: Nakabayashi Nobuo , Ishihara Kazuhiko
Published: March 2011

New nonthrombogenic polymers were designed with attention to the surface of biological membranes, that is, the surface was completely covered with phospholipids adsorbed from plasma. The polymers with phospholipid polar group, 2‐methacryloyloxyethyl phosphorylcholine polymers, could interact with phospholipids in plasma selectively and strongly. The adsorbed phospholipids on the polymer surface were concentrated, organized each other and then formed a self‐assembled biomimetic membrane surface. The surface showed excellent resistance for both protein adsorption and blood cell adhesion.
Polymerization of lactams, 89 magnesium caprolactamates as initiators of ∈‐caprolactam polymerization
Authors: Nováková Václava , Šáchová Monika , Brožek Jiří , Bernat Petr , Roda Jan
Published: March 2011

The anionic polymerization of ∈‐caprolactam initiated with magnesium initiators was studied in the interval 180–250°C. ∈‐Caprolactam magnesium bromide was much more active than magnesium di(∈‐caprolactamate) and the activity of both depended on the way of their preparation. The polymerizations obey the zero order kinetics with respect to the monomer.
The influence of thermoplastic elastomers on structure and crystallisation behaviour of polyolefin blends
Authors: Plawky Udo , Wenig Werner
Published: March 2011

The influence of a styrene‐ethylene/butylene‐styrene triblock copolymer (SEBS) on an isotactic polypropylene / polyethylene blend was investigated. For comparison binary blends with polypropylene and SEBS alone were also prepared. The blends obtained by solution mixing were characterised by small‐angle x‐ray scattering, light microscopy and dynamic mechanical analysis. The role of SEBS as matrix reinforcer or interfacial agent is composition dependent. Experimental data also reveal a different influence of SEBS on the binary blends than on the ternary blends containing polyethylene.
Driving forces for protein adsorption at solid surfaces
Authors: Norde Willem
Published: March 2011

Under most conditions proteins show a strong tendency to adsorb at interfaces. The general principles underlying the interaction between proteins and solid surfaces in an aqueous environment are discussed. These principles are illustrated by experimental results obtained with well‐defined systems. The approach is mainly based on thermodynamic arguments.
Surface modification of expanded poly(tetrafluoroethylene) by means of microwave plasma treatment for improvement of adhesion and growth of human endothelial cells
Authors: Simon F. , Hermel G. , Lunkwitz D. , Werner C. , Eichhorn K. , Jacobasch H.‐J.
Published: March 2011

Surface modification of expanded poly(tetrafluoroethylene) (ePTFE) vascular prostheses was carried out by means of low pressure microwave plasma treatment. Hydrogen/ water vapour mixtures (containing excess of hydrogen) were shown to be efficient with respect to functionalization of PTFE.

The results of treatments in dependence on various gas pressures and treatment times were detected by physicochemical techniques (zeta potential, wetting measurements) and by surface spectroscopy (XPS, ATR‐FTIR).

Furthermore, adhesion and proliferation of human endothelial cells from umbilical cord (HUVEC) onto modified ePTFE were observed in vitro in culture media. The results of this biological test of plasma treated materials correlate well with physicochemical surface parameters.
Effects of gamma and electron beam irradiation on polymer electrolytes
Authors: Okamoto Yoshiyuki , Cho Myung D.
Published: March 2011

Polymer electrolytes based on poly(ethylene oxide) and lithium salts have been widely studied in recent years. In order to enhance the room temperature ionic conductivity of PEO‐LiX complexes, various techniques, such as addition of plasticizers and crown ether, and also irradiation by γ and electron beams have been investigated. The enhancement of the conductivity by irradiation has been accounted for the decreasing of the crystallinity of PEO‐LiX. We reviewed these results and have investigated the degradation processes of PEO using Tb3+ fluorescence probes. We have also studied on the effects of irradiation of polymers such as poly(acrylic acid) (PAA), poly(methacrylic acid) (PMA) and PEO using Tb+3 fluorescence probe. Various monomers containing SO3H and COOH have been grafted on poly(ethylene oxide) using irradiation technique. The structures and ionic conductivities of Li and Na salts of irradiated products were investigated in detail.
Esterification of α‐olefins catalyzed by homogeneous and polymer supported phosphine ‐ palladium ‐ tin chloride complexes
Authors: Pan Cai‐Yuan
Published: March 2011

The polymer phosphine ligand with various crosslinkage and phosphine contents was prepared by copolymerization of diphenylvinyl‐phosphine with divinylbenzene using 2,2′ ‐azobisisobutyronitrile (AIBN) as initiator. Linear methyl heptanoate in high yield was obtained from hexene‐l catalyzed by polymer‐supported and homogeneous phosphine‐palladium‐tin chloride complex. Comparison with the homogeneous catalyst, the polymer catalyst had higher activity and almost the same selectivity. The effects of the catalyst composition, the structure of the polymer ligand and other experimental variables on the catalytic activity and selectivity of the polymer catalyst have been examined, and are discussed in relation to the mode of this catalysis.