bluuebunny/crossref_metadata_2025 huggingface dataset:
Electro‐optical properties and nonlinear response of side chain liquid crystalline polymers
Authors: Gonin D. , Guichard B. , Noël C. , Kajzar F.
Published: March 2011

Among the NLO processes that have been studied, one of the most visually dramatic is the frequency doubling. In the field of optical information storage this process can provide the conversion of near‐infrared laser light from diode lasers into deep blue light. Compared to the more traditional inorganic NLO materials, polymers with polarizable aromatic pendant side groups are increasingly being recognized as the materials of the future. Recently it has been pointed out that the axial ordering spontaneously present in nematic and smectic A polymers can be used to enhance field‐induced polar ordering by elongating the orientational distribution function along the electric field direction. Depending on the value of the microscopic order parameters 2 and 4, the performance may be improved by a factor of 1 to 5 by using LCPs instead of ordinary amorphous polymers for SHG.1‐4)

Interesting results have been obtained for copolyethers prepared by chemical modification of polyepichlorohydrin with classical 4‐cyano‐4'‐hydroxybiphenyl mesogenic group which possesses NLO properties itself.5‐8) These copolyethers afford the opportunity to fine‐tune the polymer properties by varying the concentration of the mesogenic side groups. As the concentration is increased, we move from a purely isotropic polymer to a nematic polymer. Spin‐coated films have been activated using the corona poling technique and the order parameters 2 have been determined from optical absorption spectra. The second harmonic coefficients d33 and d31 have been measured and compared with different statistical models. In view of the great practical importance, characterization of the wavelength dispersion has been carried out. It agrees well with the two‐level approximation model. The dynamics of optical SHG has been investigated. It has been shown that both the presence of LC character in the material and the temperature at which the films are stored below Tg are important in determining the stability of the SH coefficients.

A polyacrylate and a polymethacrylate bearing the same 4‐cyanobiphenyl‐based side groups have also been studied.7‐8) Of particular interest is the fact that the former is nematic while the latter is purely isotropic at rest, the addition of a methyl group to each structural unit of the polyacrylate backbone creating a higher conformational barrier to mesogen packing. Studies of the temporal and thermal characteristics of the poling process have been performed to:

•understand and control the poling process with the intention of maximizing poling induced nonlinearity and stability.

•elucidate the influence of the polymer backbone, our data including the use of the same mesogenic unit attached to increasing flexible backbones (e.g. polymethacrylate and polyether).

•establish if, in the isotropic cases, noticeable axial order can be induced by the poling field, especially when the system is pulled through nematic/isotropic transition by the electric field.
Self‐assembly via a complex phase transition in mixtures of polystyrene‐block ‐polybutadiene block copolymer and poly(methyl vinyl ether)
Authors: Hashimoto Takeji , Izumitani Tatsuo , Oono Katsuaki
Published: March 2011

The self‐assembly of a binary mixture of polystyreneblock‐polybutadiene (SB) and poly(methyl vinyl ether) (PVME) was studied by transmission electron microscopy and time‐resolved light scattering. The self‐assembly studied involved first microphase separation, in which a microdomain structure composed of polybutadiene block chains (PB) was formed in a matrix composed of polystyrene block chains (PS) and PVME homopolymers, and subsequently macrophase separation of the PVME from the microdomain phase of SB. The microphase separation was induced in a film preparation process using a solution cast method at room temperature. The macrophase separation was induced by rapidly heating the film specimens to above a critical temperature where PVME and PS undergo spinodal decomposition (SD). This complex phase transition, involving microphase separation followed by macrophase separation, was found to generate a superlattice structure (or a modulated structure) with two characteristic spacings: Amacro associated with the SD and Amicro associated with the microphase separation, both being generally time‐dependent. The growth of the “macrodomains” was found to be pinned at Amacro ˜ 840 nm due to the elastic effect of the microdomain structure. The microdomain structure with Amicro ˜ 57 nm was found to undergo a morphological transition (a transition between two ordered phases of block copolymers) as a consequence of the local composition change of the two polymers induced by the SD.
Nematic, smectic and columnar phases of main‐chain liquid crystal polyethers
Authors: Ungar Goran , Zhou Jianping , Percec Virgil , Chu Peihwei
Published: March 2011

A number of interesting thermotropic mesophases and transitions occur in main‐chain polyethers and copolyethers based on aliphatic spacers and various semi‐flexible mesogens of the general 1‐(4'‐hydroxyphenyl)‐2‐(2‐R‐4‐hydroxyphenyl)ethane (RBPE) or 1‐(4'‐hydroxybiphenyl‐4‐yl)‐2‐(4‐hydroxyphenyl)propane (TPP) type. The unusual effects described here are (i) nematic‐nematic transition, (ii) smectic‐B (crystal‐B) phase and its shear‐induced orientation, (iii) calamitic columnar phase, and (iv) nematic‐columnar phase sequence.
Optical rheometry of multicomponent polymer liquids
Authors: Fuller Gerald G.
Published: March 2011

Recent advances in optical rheometric techniques are described, and applications of the methods are presented that motivate their use in elucidating the structure and dynamics of complex, polymeric liquids. Spectroscopic methods, such as infrared dichroism and 2‐dimensional Raman scattering, which provide information concerning bond‐level orientation dynamics are presented. In addition, the combination of birefringence and stress measurements is demonstrated to be capable of extracting the component dynamics in some multicomponent systems. Examples of the use of these methods include orientation in block copolymers and compatible blends.
Molecular modeling of polymers, 14 quantitative structure‐property relationship analyses of multicomponent systems containing polymers
Authors: Hopfinger A. J. , Koehler M. G. , Rogers David
Published: March 2011

One general class of polymer modeling applications involves materials which are large, in terms of molecular degrees of freedom, and poorly defined in terms of composition and morphology. Such materials are often multicomponent with respect to number of distinct polymers, fillers, additives, etc. Two obstacles limit the modeling of these materials. First, one normally does not have any idea about the key physicochemical molecular properties governing the system. Second, the functional dependence of the target properties of the material upon the key physicochemical molecular properties is usually totally unknown. Torsion angle unit (TAU) theory, a molecular decomposition technique, permits an arbitrarily large number of physicochemical properties to be computed in an open‐ended fashion, and thus addresses the first problem. Genetic function approximation (GFA) analysis tackles the second problem by efficiently exploring any desired number of functional relationships between target properties and physicochemical molecular properties. Case studies of (TAU theory)‐(GFA analysis) applications to estimate glass, Tg, and crystal‐melt, Tm, transition temperatures will be described.
Molecular interactions at the interface in blends of ester groups‐functionalized polyolefins
Authors: Aglietto M. , Benedetti E. , Ruggeri G. , Ciardelli F. , Pracella M. , D'Alessio A.
Published: March 2011

Due to the apolarity of the aliphatic backbones, unmodified polyolefins are scarcely miscible with most of other polymers. The functionalization of preformed polyolefins is a way which has been successfully followed to improve the polymer miscibility.

The functionalization of linear low density polyethylene (LLDPE) and ethylene‐propylene copolymers (EP), with diethyl maleate (DEM) and dicumyl peroxide (DCP) as radical initiator, gives products containing up to 2–5 mol % of well defined functional groups (2‐diethyl succinate).

Intermolecular interactions of these functional groups are characterized by comparison with suitable low‐molecular‐weight structural models in the presence of different solvents containing acidic hydrogen atoms.

On the basis of these indication evidences of interface molecular interactions in blends with halogenated polymers are described between the functionalized polyolefins and poly(vinyl chloride) (PVC), poly(vinylidene fluoride) (PVDF) or vinylidene fluoride‐hexafluoropropene copolymer obtained in semiindustrial Brabender mixers.

It is shown that a smooth functionalization of the polyolefins can modify the phase behaviour and structure of these systems. The FT‐IR microanalysis supports the occurrence of partial miscibility phenomena which can be accounted for by specific intermolecular interactions involving the inserted functional groups and occurring mainly at the interfaces between domains of polyolefins and of the halogen‐containing polymers.
Structural analysis of polysaccharides and polysaccharide derivatives
Authors: Mischnick Petra
Published: March 2011

The general strategies and methods applied in the analysis of the primary structure of polysaccharides and derivatives are shortly lined out. Methods involving complete degradation of the polysaccharide are discussed in more detail. Advantages of the reductive‐cleavage method compared to classical methylation analysis are illustrated by giving some examples of application.
NMR Studies on the structure of cellulose. 2‐dimensional solid state NMR approach
Authors: Erata Tomoki , Shikano Tamio , Shimizu Yu‐Ichi , Takai Mitsuo , Hayashi Jisuke
Published: March 2011

Two‐dimensional C‐H correlation NMR spectra are presented for the native cellulose types Iα and Iβ from Cladophora sp. A remarkable difference of correlation peaks between Iα and Iβ was observed, which indicates an essential structure difference between the two types of native cellulose.
Functionality of the β(1,4) Glycosidic Linkage in Polysaccharides
Authors: Burchard Walther , Schulz Liane
Published: March 2011

The equatorial configuration of the β(1,4)‐glycosidic bond predestines a stretched chain conformation. These topological characteristics form the basis for laterally aggregated supramolecular structures in the solid state as well as in the concentrated solution regime. Partially substituted derivatives develop water solubility, but the dissolution process stops at a certain colloidal level. The aggregates show structural properties which are best described by a fringed micelle. These objects are built up of laterally aggregated chains forming a stem and have a peripheral shell of dangling chain sections. The striking dynamic properties indicate no segment interpenetration, and the particles lose gradually their shell mobility as the overlap concentration is exceeded.
Gel‐sol transition in gellan aqueous solutions
Authors: Miyoshi Emako , Takaya Tomohisa , Nishinari Katsuyoshi
Published: March 2011

Gel‐sol transition of sodium type gellan solutions with and without salts is studied by dynamic viscoelastic measurements and differential scanning calorimetry (DSC). Mechanical spectra show that gellan aqueous solutions behave as an entangled polymer solution in the concentration range around 2 wt.‐% at temperatures >15°C and as a weak gel below this temperature. Concentrated solutions (> 3 wt.‐%) show a true gel behavior below 30°C. The two step transition is observed for 2∼3 wt.‐% gellan aqueous solutions in thermal scanning rheological (TSR) measurements; the transition at a higher temperature is attributed to a coil‐helix transition whilst the transition at a lower temperature is attributed to sol‐gel transition. The transition observed in dilute solutions of gellan is attributed to the coil‐helix transition whilst the sol‐gel transition occurs simultaneously with coil‐helix transition in more concentrated solutions (>3 wt.‐%). The sol‐gel transition temperature shifts to higher temperatures with increasing concentration of the added salts. Junction zones formed in the presence of divalent cations are far more heat resistant than those with monovalent cations judging from both DSC and TSR, however, the possibility of the formation of junction zones by covalent bonds or by ionic bonds is excluded.
Inclusion compounds of derivatized amyloses
Authors: Kubik Stefan , Höller Olaf , Steinert Andreas , Tolksdorf Martin , Wulff Günter
Published: March 2011

Inclusion complexes of slightly hydroxypropylated amylose with organic guest molecules have been investigated by means of c.d. spectroscopy and microcalorimetry in aqueous solution. From these results, the structure of the complexes and the mechanism of their fomation are deduced. It is concluded that amylose can adjust its helix conformation to the shape and structure of the guest molecule included. Investigations about intramolecular and intermolecular crosslinking of amylose indicate that the complexing behavior of amylose can be manipulated specifically.
Coordination equilibria in transition metal based cellulose solvents
Authors: Burger Joachim , Kettenbach Gerhard , Klüfers Peter
Published: March 2011

Taking into account the coordination chemistry of divalent palladium and nickel, two new cellulose solvents have been developed. Pd‐en is an aqueous solution of the ethylenediamine palladium complex [(en)Pd(OH)2]. Low molecular diols are deprotonated twice in Pd‐en and form a five membered chelate ring with the transition metal. Cellulose dissolves in Pd‐en to give a yellow solution, which allows light scattering analysis. NMR investigation of the solutions are simplified due to the diamagnetism of palladium(II) complexes. — The analysis of solution equilibria is essential in the development of complexing polysaccharide solvents. This feature is demonstrated by means of the new cellulose solvent Ni‐tren, which is an aqueous solution containing tris(2‐aminoethyl)amine, nickel salt and hydroxide in a molar ratio of ≥1:1:2. The difference in the cellulose solving mechanism between Ni‐tren and the long known solvents ‘nioxen’ and ‘nioxam’ developed by Jayme in the 1950ths is outlined. The question, wether or not the dissolution of cellulose in a complexing solvent is a derivatization, is discussed.
Biological control of cellulose
Authors: Tajima Kenji , Fujiwara Masashi , Takai Mitsuo
Published: March 2011

The enhancement of bacterial cellulose (BC) productivity using sucrose as a carbon source has been obtained by the co‐cultivation of two different types of acetic acid bacteria. BC yields for the given mix ratio of bacteria were larger than that of control. The contents of water‐soluble polymer (WSP) in the BC composites (BCCs) are a range of 5–30 wt‐%. This will be due to the formation of glucose and fructose through the hydrolysis of sucrose by sucrase secreted from Acetobacter sp. In addition, this preparation method would be applied to synthesize a new type of BC having both high biodegradability and other functions.
Synthesis of functional polymers bearing pendant mono‐and oligo‐saccharide residues
Authors: Minoda Masahiko , Yamaoka Katsushi , Yamada Kenji , Takaragi Akira , Miyamoto Takeaki
Published: March 2011

The present paper focuses on (i) a new synthetic methodology to prepare vinyl ether‐based synthetic glycoconjugates (glycopolymers) with well‐controlled structure, and on (ii) the application of glycopolymers bearing modified disaccharide residue as thermotropic liquid crystalline (LC) materials. Two vinyl ethers (VEs) having pendant glucose residues with their hydroxyl functions protected by acetyl and isopropylidene groups, respectively, were found to undergo living cationic polymerization initiated by a HI/ZnI2‐initiating system. Deprotection of the resultant monodisperse polymers led to water‐soluble polymers bearing a pendant glucose residue. Sequential living block copolymerization of glucose‐containing VE and alkyl VE, and subsequent deprotection afforded an amphiphilic block copolymer of well‐controlled structure. Transmission electron microscopic observation of its cast thin film revealed microphase‐separated surface morphologies that varied with varying segment composition ratio. A VE substituted with a heptadecanoated cellobiose pendant was independently prepared, and was cationically polymerized to give a thermotropic LC polymer. From X‐ray analysis, the mesophase was assigned to a discotic columnar in type, in which each main chain, extended due to the steric repulsion between the neighboring bulky pendants, was surrounded by three discotic columns.
Dynamic mechanical investigations of different substituted cellulose o‐silyl ethers
Authors: Henze‐Wethkamp Heinrich , Zugenmaier Peter , Stein Armin , Klemm Dieter
Published: March 2011

In contrast to many cellulose derivatives, the cellulose O‐silyl ethers with bulky side groups exhibit scarcely a change in glass transition temperature by a variation of the degree of substitution (DS) or degree of polymerization (DP) or by introducing phenyl carbamate groups for the remaining hydroxyls along the main chain. However, a substitution of these hydroxyls by flexible acetate groups lowers the glass transition temperature considerably. The secondary dispersion (relaxation) behavior is strongly influenced by the various substituents and can be correlated to specific motions of the molecules. The dynamic mechanical properties are also dependent on the kind of preconditioning of the samples.
Physical aspects of polymer stabilization
Authors: Földes Enikó
Published: March 2011

Transport properties of additives in polymers were studied by measuring the diffusion rate and solubility of different antioxidants in ethylene polymers. Correlation was found between the diffusion rate and the fractional free‐volume of the noncrystalline phase of polymer, as well as the specific volume of diffusant. The measured solubility values were evaluated by the extended thermodynamic theory of solution of solids.
Blends of synthetic and natural polymers as special performance materials
Authors: Giusti Paolo , Lazzeri Luigi , Cascone Maria Grazia , Seggiani Maurizia
Published: March 2011

The interest for blends of synthetic and natural polymers is growing and several applications in many different fields are now becoming evident. The biological‐synthetic polymers interactions play a relevant role in controlling the mechanism that constitutes the basis of biocompatibility of materials used in medicine. This work concerns with the preparation and chemico‐physical and mechanical characterization of blends in which the biological component is hyaluronic acid or its benzyl ester derivatives, and the synthetic component is poly(vinyl alcohol) or ethylene‐vinyl alcohol copolymers.
Drop deformation in polymer blends during uniaxial elongational flow
Authors: Delaby I. , Froelich D. , Muller R.
Published: March 2011

The deformation in uniaxial elongational flow of dispersed droplets in immiscible molten polymer blends was studied for negligible interfacial tension and for viscosity ratio p = η(drop)/η(matrix) between 0.005 and 13, with an original method based on quenching elongated specimens. Although drop deformation (drop major axis over initial diameter) was in the range 1 < λd < 5, a good overall agreement was found with the small deformation Newtonian theory, which predicts that the drop versus matrix deformation ranges from 5/3 to 0 when p increases from 0 to infinity. The theoretical prediction that for p lower than 1, the droplet should deform more than the faraway surrounding matrix, with a limiting ratio of 5/3 at vanishing droplet viscosity, was experimentally verified.
New polyolefin plastomers and elastomers made with insite™ technology: Structure ‐ property relationship and benefits in flexible thermoplastic applications
Authors: Batistini Antonio
Published: March 2011

The polymerization of ethylene and 1‐octene by a recently developed homogeneous constrained geometry catalyst produces elastomers and plastomers with narrow molecular weight distributions, short chain branching compositions and the unique presence of long chain branching. Particular morphology and network structures in function of density give rise to excellent mechanical and physical properties which make these co‐polymers suitable for a broad range of consumer durable and packaging applications.
Multiphase polypropenes prepared by reactive blending
Authors: Mülhaupt Rolf , Stricker Florian , Barghoorn Peter , Rösch Joachim
Published: March 2011

Multiphase polypropenes, reinforced with rigid SiO2 or polyamide 6 (PA6) microparticles, respectively, were prepared to study the influence of morphology and elastomeric interlayers on toughness/stiffness balance. Reactive processing technology was developed to in‐situ encapsulate rigid microphases in elastomeric shells. Such core/shell‐type morphologies were compared with those comprising simultaneously dispersed separate rigid and rubbery microphases. Unusual property synergisms of polypropene/polyamide 6 (70 v. %/30 v. %) blends were attributed to the formation of cocontinuous self‐assemblies of core/shell‐type PA6/SEBS microparticles.
Properties and application of luster pigments
Authors: Ostertag Werner , Mronga Norbert
Published: March 2011

In contrast to conventional pigments, which interact with light by absorption and/or diffuse scattering, effect or luster pigments show optical properties that are due to specular reflection of light by aligned flaky particles. Their main property is goniochromaticity, i.e. the change of lightness and/or color hue with the viewing angle of the observer. The paper describes the different type of luster pigments, their optical properties and applications and manufacturing methods.
Computer simulations of energetic and conformational changes in polymer systems
Authors: Kreitmeier Stefan , Wittkop Markus , Göritz Dietmar
Published: March 2011

Using a Monte Carlo method, the deformation behavior of single polymer coils was investigated. Random walks were used to verify the stretching procedure. The prediction of Pincus and DeGennes for self avoiding walks could be confirmed. The simulations at finite temperatures showed a transition from entropy to energy controlled behavior. The coils underwent a clear nonaffine deformation pattern.
Molecular recognition directed self‐assembly of tubular supramolecular architectures from building blocks containing monodendrons as exo‐receptors and crown‐ or pseudo‐crown‐ethers as endo‐receptors
Authors: Percec Virgil , Johansson Gary , Schlueter Douglas , Ronda Joan C. , Ungar Goran
Published: March 2011

The principles of self‐assembly of tapered exo‐receptors constructed from monodendrons containing crown‐ether, oligooxyethylenic groups and polymer backbones as endo‐receptors into tubular supramolecular architectures are described with selected examples. In the case of polymers with flexible backbones it is suggested that a helical chain conformation is induced during the assembly of its own tapered side groups. This mechanism is supported by the enhanced self‐assembling ability of tapered side groups attached to a backbone with rigid helical conformation.
Spectroscopic studies of conducting polymers
Authors: Furukawa Yukio , Sakamoto Akira , Tasumi Mitsuo
Published: March 2011

Electronic and vibrational spectra of poly(p‐phenylenevinylene) doped with donors or acceptors have been studied, together with the spectra obtained for the radical ions and divalent ions of its oligomers. The electronic absorption spectra of doped poly(p‐phenylenevinylene) in the region from visible to near‐infrared show two bands for the H2SO4‐doped species and one very broad band for the Na‐doped species. On the basis of the analyses of resonance Raman spectra, the two electronic absorption bands of the H2SO4‐doped species are attributed to a polaron‐lattice structure, whereas the broad band of the Na‐doped species is attributed to overlapping absorptions associated with localized electronic levels of polarons and bipolarons. A Pauli spin susceptibility of the H2SO4‐doped species is explained by the polaron‐lattice structure.
Physical properties and processing conditions correlations of the ldpe/lldpe tubular blown films
Authors: Campbell Gregory A. , Babel Ashok K.
Published: March 2011

Experiments are carried out to verify a theory developed to correlate the strain history of the polymer during film blowing to the ultimate physical properties of the film. The theory predicts that the amount of strain put into the film once it starts to freeze, defined as strain in the amorphous region and the plastic strain, has a dominant effect on the film properties. Two grades of low and linear low density polyethylene, experimental resins supplied by Mobil chemical company, were used to produce the blown film yielding a 1.25 mil film at the for all experimental runs. Film surface and bulk temperatures, along the machine direction and around the bubble, were measured using the infra‐red techniques to identify the points where film starts to crystallize. A video digitization technique was used to measure the bubble kinematics. Film properties were measured using standard ASTM methods. The results indicate a correlation between the amount of strain and a measure of stress with ultimate physical properties of the blown film. This principle leads to the correlation of both the machine and transverse film properties on the same surface. The results obtained can potentially be exploited by designing the blown‐film equipment and processing conditions such that optimal bubble stretching produces desired film properties.
Macromolecularization of fullerenes and the charge transfer complex formation of fullerenes with polymers having electron‐donating or electron‐accepting moieties
Authors: Li Fu‐Mian
Published: March 2011

C60 was bonded to allylamine homopolymer (PALA) and its copolymers with styrene, 2‐hydroxypropyl methacrylate etc. as a pendant functional group. The polyallylamine bonded C60 displays fluorescence at room temperature although C60 does not in itself. This may be due to the lessening of highly symmetrical shape of C60. Some C60‐amine adducts are prepared as the model of polyallylamine‐C60 for the clarification. C60 doped poly(tetrahydrofurfuryl methacrylate) film has been prepared and its optical non‐linearity has been investigated. The charge transfer complexes formation of C60 with polymers having electron‐donating chromophore moieties such as poly(dimethylaminostyrene), poly(acryloylphenothiazine), poly(acryloylphenoxazine) and poly(styrene‐co‐dimethylaminophenylmaleimide) as well as with polymer having electron‐accepting chromophore moiety poly(cyanophenylacrylamide) have been manifested.
Synthesis and application of inorganic/organic composite materials
Authors: Schmidt Helmut K.
Published: March 2011

A new type of inorganic‐organic composite has been developed using organic monomeric or polymerizable silanes (with appropriate organic groupings like double bonds or epoxides) as monomers or in situ prepared or separately added nano‐scale ceramic or metal particles. Due to the small size of the particulate phase, these composites are still highly transparent but show properties at least partially to be attributed to the inorganic phase. The introduction of special functions into these materials has been used for the fabrication of interesting functions like non‐linear optical properties, low surface free energy coatings, controlled release properties or special mechanical properties (scratch resistance).
Biochemical and biomedical application of monodisperse polymer particles
Authors: Ugelstad John , Stenstad Per , Kilaas Lars , Prestvik Wenche S. , Rian Anne , Nustad Kjell , Herje Ragnhild , Berge Arvid
Published: March 2011

Macroporous particles with large pores are used for size exclusion chromatography of carbohydrates with very high molecular weights. Macroporous particles of different sizes are used for multiple immunofluorometric analysis by flow cytometry. Porous magnetic particles with protein A coupled to the surface of the pores combine a high capacity in binding of IgG with easy handling of the particles. Magnetic beads with boronic acid coupled to the surface are applied for selective isolation of subclasses of cells. The beads are detached from the cells by addition of sorbitol, leaving free, pure cell fractions in good yield. The use of magnetic particles in molecular biology is described.
Organic electroluminescent and nonlinear optical materials
Authors: Saito Shogo , Tsutsui Tetsuo , Era Masanao
Published: March 2011

The multilayer electroluminescent(EL) devices composed of vacuum‐sublimed organic films are discussed with the aims of achieving high luminance and proposing an optical micro‐cavity. For the former purpose, requirements for confinements of carriers and excitons within the thin emissive layer are shown by taking accounts of ionization potentials, electron affinities and excitation energies in organic thin films. Concerning the interference effect of emitted light, we show the variation in the intensity of emission and a strongly directional light from the micro‐cavity. Second‐order nonlinear optical(NLO) films are designed by preparing noncentrosymmetric LB multilayers composed of an pyrazine derivative with large hyperpolarizability and arachidic acid. Third‐order nonlinear optical(NLO) films are proposed by using polyarylenevinylene films. In order to fabricate excellent third‐order nonlinear optical(NLO) films, highly oriented polyarylenevinylene films are prepared by using a LB technique.
Polypropylenimine dendrimers: Improved synthesis and characterization
Authors: De Brabander E. M. M. , Brackman J. , Mure‐Mak M. , De Man H. , Hogeweg M. , Keulen J. , Scherrenberg R. , Coussens B. , Mengerink Y. , van Der Wal S. J.
Published: March 2011

Both the Michael addition and the hydrogenation steps in the large scale synthesis of polypropylenimine dendrimers have been improved: by adding ammonia during the hydrogenations the substrate concentrations can be increased 8 times, the catalyst concentration can be lowered 10 times and the average selectivity remains > 99.5% per conversion. The dimensions of the dendrimers have been studied with SANS and with molecular calculations.
Dendritic polyols based on carbosilanes ‐ lipophilic dendrimers with hydrophilic skin
Authors: Frey Holger , Lorenz Klaus , Mülhaupt Rolf , Rapp Uwe , Mayer‐Posner Franz J.
Published: March 2011

Carbosilane dendrimers with up to 108 end groups were prepared by a divergent synthetic route via repeated alternating Grignard‐reaction with allylmagnesium bromide and hydrosilylation. Quantitative hydroboration of the dendrimers was achieved with 9‐BBN/H2O2,OH−. Employing this synthetic route, rather monodisperse dendritic polyols with lipophilic carbosilane core and hydrophilic shell were prepared. All dendrimers were characterized with MALDI‐TOF, showing low polydispersities. The novel dendritic polyols constitute interesting molecular scaffolds for the preparation of unusual supermolecules. As an example, reaction with cholesteryl chloro‐formiate was used to prepare a series of dendrimers with 12, 36 and 108 mesogenic cholesteryl end groups.
Polyrotaxanes: Past, present and future
Authors: Gibson Harry W. , Liu Shu
Published: March 2011

The threading process in polysebacate‐crown ether rotaxanes prepared by the acid chloride method was examined by systematic study of the effects of 1) the size of the macrocycle, 2) the equilibration time between the diol and the macrocycle before addition of sebacoyl chloride, 3) the molar ratio of crown ether to diol, 4) the length of the α,ω‐diol and 5) the temperature of equilibration and reaction. It was concluded that the threading process is based on hydrogen bonding interactions of the diol with the crown ether, predisposing the latter to threading as the ester bond is formed. The lack of “stoppers” or “knots” at the chain ends is believed to allow loss of macrocycles in the initial precipitation, after which loss of macrocycles is very slow due to chain folding. All of these polyester rotaxanes, except the 30‐crown‐10 case, display crystalline phases for both the backbone and the cyclic components. All of the polyrotaxanes complex alkali metal ions.
Stereocomplex formation in AB DI‐block copolymers of poly(ϵ‐caprolactone) (a) and poly(lactide)(B)
Authors: Stevels Willem M. , Ankoné Marc J. K. , Dijkstra Pieter J. , Feijen Jan
Published: March 2011

The thermal properties of two series of AB di‐block copolymers of poly(ϵ‐caprolactone) (A) and poly(lactide) (B) and their blends were studied. Each series contained poly(lactide) blocks of opposite chirality. The length of the poly(ϵ‐caprolactone) blocks was not varied (DP = 70), whereas the poly(lactide) blocks were of varying length (DP = 5 − 80). Blends of polymers containing blocks of opposite chirality were prepared by mixing in solution. The melting temperature of the PLA phase was raised by approximately 55 °C in the blends due to stereocomplex formation. The melting temperatures of the crystalline PCL and PLA phases strongly depended on the composition of the block copolymers.
Optical and charge transport properties of DI‐n‐hexyl substituted polysilylene and polygermylene
Authors: van Der Laan Garrelt P. , De Haas Matthijs P. , van Walree Cornelis A. , van Slageren Joris , Jenneskens Leonardus W. , Frey Holger
Published: March 2011

Optical and charge transport properties of poly(di‐n‐hexylsilylene), PD6S, and poly(di‐n‐hexylgermylene), PD6G, have been studied. The main‐chain σ‐conjugation in both polymers leads to intense σ‐σ* UV‐absorptions. A hypsochromic shift is observed for both polymers at the transition from a crystalline solid phase to a columnar mesophase. This transition is accompanied by disordering of the polymer backbone which results in a decrease of the radiation induced microwave conductivity by a factor of 26 for PD6S and a factor of 4 for PD6G. In the disordered mesophase a charge carrier mobility of ca. 0.6×106 m2/Vs is found for both polymers. Charge carrier mobilities of 15×106 m2/Vs and 2.4×10‐6.m2/Vs are found in the crystalline phase of PD6S and PD6G respectively, indicating a more ordered backbone for PD6S compared with PD6G.
Spectroscopic and thermodynamic characterization of the adsorption of plasma proteins onto cellulosic substrates
Authors: Müller M. , Werner C. , Grundke K. , Eichhorn K. J. , Jacobasch H.‐J.
Published: March 2011

The sorption of the plasma proteins human serum albumin (HSA) and human fibrinogen (FIB) onto hemodialytic cellulosic substrates was investigated by the surface sensitive ATR‐FTIR‐spectroscopy. By means of this method we monitored the protein sorption kinetics onto acetylated and unmodified cellulose (AKZO‐NOBEL). Furthermore, secondary structure alterations of the adsorbed proteins as well as changes of the composition in sorbed layers consisting of two proteins were detected. These findings were compared with results of the zeta potential and contact angle measurements on comparable sorption experiments.
Water soluble nucleic acid analogs: Preparation and properties
Authors: Takemoto Kiichi
Published: March 2011

In order to prepare water soluble natural and synthetic polymers, which contain nucleic acid base units as the functional side groups, a different sort of polymers, such as poly(ethyleneimine), poly(amino acids) and so on were used as the base materials. The properties of the polymers derived, in particular the specific interaction between nucleic acid base containing complementary polymers was studied in detail. Introduction of the base units onto hyaluronic acid was also carried out. Applicabilities of these polymers obtained, for example as the controlled release system by using reversible photodimerization reaction of thymine bases were also shown.
Polymeric prodrugs of mitomycin C
Authors: Soyez Heidi , Schacht Etienne , De Marre Anne , Seymour Leonard W.
Published: March 2011

Poly‐[N‐(2‐hydroxyethyl)‐L‐glutamine] (PHEG) prodrugs of the cytotoxic agent Mitomycin C were synthesized using peptidyl spacers to link the drug to the polymeric carrier. The influence on the length and detailed structure of the oligopeptide on the rate of drug release was investigated in buffer, in the presence of lysosomal enzymes (tritosomes, cathepsin B and D) and metalloprotease type IV collagenase. It was observed that tetra‐ and hexapeptide based conjugates generally release Mitomycin C (MMC) more effectively than tripeptide derivatives. The gly‐phe‐ala‐leu conjugate released MMC very rapidly both in presence of lysosomal enzymes and collagenase IV. Only in the presence of the aspartic protease cathepsin D, the gly‐phe‐leu‐gly‐phe‐leu derivative turned out to be a better substrate. In vivo studies against C26 solid tumour bearing mice suggest that PHEG‐spacer‐MMC conjugates act as prodrugs of MMC: antitumour efficacy of the macromolecular prodrugs was better than free MMC both in inhibition of tumour growth and increasing survival.
Micro and nano layered polymers
Authors: Baer Eric
Published: March 2011

The crazing behavior of coextruded microlayer sheets consisting of alternating layers of polycarbonate (PC) and styreneacrylonitrile copolymer (SAN) was investigated as a function of PC and SAN layer thicknesses. In this study, the total sheet thickness remained essentially constant and the PC and SAN layer thicknesses were changed by varying both the total number of layers from 49 to 1857 and the PC/SAN volume ratio.[1,2] Photographs of the deformation processes were obtained when microspecimens were deformed under an optical microscope. Three different types of crazing behavior were identified: single crazes randomly distributed in the SAN layers, doublets consisting of two aligned crazes in neighboring SAN layers, and craze arrays with many aligned crazes in neighboring SAN layers. The transition from single crazes to doublets was observed when the PC layer thickness was decreased to 6 microns. Craze array development was prevalent in composites with PC layer thickness less than 1.3 microns. It was concluded that SAN layer thickness was not a factor in formation of arrays and doublets; formation of craze doublets and craze arrays was dependent only upon PC layer thickness.
Morphological alignment of liquid crystalline conducting polyacetylene derivatives
Authors: Akagi Kazuo , Shirakawa Hideki
Published: March 2011

We have synthesized novel liquid crystalline conducting polymers by introducing liquid crystalline group into acetylene monomer and polymerizing them with Ziegler‐Natta [Fe(acac)3 ‐ AlEt3] and metathesis [M0Cl5 ‐ Ph4Sn] catalysts. The liquid crystalline group is composed of a phenylcyclohexyl (PCH) or biphenyl (BP) moiety as a mesogenic core, a trimethylene chain [‐(CH2)3‐] as a spacer, and an alkyl chain (‐CnH2n+1, n = 2, 3, 5 ∼ 8) as a terminal group. The polymers are abbreviated as PPCHn03A and PBPn03A.

All polymers prepared exhibited solubility in organic solvents and smectic liquid crystallinity characterized with fan‐shaped texture in polarizing optical microscopy. Phase transitions and the corresponding enthalpy changes were also evaluated by means of differential scanning calorimetry (DSC). Macroscopic alignments of the polymers were performed in the liquid crystalline phase by shear‐stress or magnetic force field of 0.7 − 1.0 tesla, which resulted in an enhancement by two orders in electrical conductivity of iodine‐doped cast films. Changes of the electronic and geometrical structures of the polymer upon the iodine‐doping were elucidated by examining the effective conjugation length of a polyene chain, cis and trans thermal isomerization, and spin distribution of unpaired electrons through ultraviolet / visible (UV‐Vis) and electron spin resonance (ESR) measurements.
On the formation of liquid crystalline texture in epoxy resins
Authors: Grebowicz Janusz S.
Published: March 2011

Three epoxy resins and two curing agents were studied in their monomeric as well as polymeric states. Two monomers were monotropic liquid crystals. Characterization of liquid crystallinity before, during and after curing reaction was carried out by DSC, optical microscopy and WAXS. It was found that LC texture develops in every epoxy/(curing agent) system studied in this work. Nucleation and growth is a physical mechanism for the formation of initial liquid crystallinity. The final texture is not well defined and likely contains nematic, poorly ordered smectic and isotropic phases. Schematic diagram of the possible states of LCTs is discussed.
Synthesis of biodegradable polymers catalyzed by macromolecule ‐ bimetal complexes
Authors: Yang Shu‐Ying , Fang Xing‐Gao , Chen Li‐Ban
Published: March 2011

A series of biodegradablc modified aliphatic polycarbonates were synthesized from carbon dioxide and relevant comonomers using a macromolecule ‐ bimetallic catalyst. The work was done to help the elimination of the pollution both from polymeric rubbish and from the greenhouse gas CO2.
Polymeric complex membranes for olefin/paraffin separation
Authors: Hsiue Ging‐Ho , Yang Jin‐Sheng
Published: March 2011

Semi‐crystalline polyethylene (PE), rubbery silicone rubber (SR) and glassy poly[(l‐trimethylsilyl)‐l‐propyne] (PTMSP) were modified for olefin/paraffin separation. The polymers were first grafted with the acrylic acid (AA) and then incorporated with silver ions for forming the complex membranes such as PE‐g‐AA‐Ag+, SR‐g‐AA‐Ag+ and PTMSP‐g‐AA‐Ag+ The complex membranes were activated by glycerol solvation and subsequently showed high selectivity in olefin/paraffin separation. The silver ion distribution, the kinetics of olefin binding to PE‐g‐AA‐Ag+, the gas permeation properties and the sorption behaviors were studied. A novel dry complex membrane for olefin/paraffin separation based on AgClO4 complexing with PTMSP main‐chain was also studied.
Analysis of charge transfer distance between Ru(bpy)32+ complexes incorporated into a nafion film as studied by spectrocyclic voltammogram
Authors: Zhang Jian , Yagi Masayuki , Kaneko Masao
Published: March 2011

An ITO electrode was coated by a Nafion film incorporating Ru(bpy)32+ complex as redox centers either by mixture casting method, adsorption method, or swelling method and the electrochemical reactivity of the modified electrode was determined by the in‐situ spectrocyclic voltammogram (SCV) in a sodium perchlorate aqueous solution at pH 1.2. A modified Poisson statistics equation was used to estimate the charge transfer distance (Ro) between the Ru(bpy)32+ complexes. The estimated charge transfer distances for the electrodes prepared by swelling method (Ro = 1.63 nm for the electrode modified in M/W 1:10, and 1.69 nm in M/W 1:2) and adsorption method (Ro = 1.61 nm) were longer than that for mixture casting method (Ro = 1.5 nm). Based on the different procedure of Ru(bpy)32+ complex incorporation in the Nafion film, the reasons that affect the apparent charge transfer distance were discussed.
Molecular design of catalysts on the basis of functionalized poly(ethylene oxide) and block copolymers of ethylene oxide and propylene oxide
Authors: Karakhanov E.A. , Maksimov A.L. , Predeina V.V. , Utukin A.M. , Filippova T. Yu.
Published: March 2011

Transition metal complexes based on polyethylene oxide and copolymers of ethylene oxide and propylene oxide functionalized by dipyridyl, acetylacetone and catechol have been prepared. Macrocomplexes showed high activity and selectivity as catalysts in oxidation of cyclohexane, hydroxylation of benzene, epoxidation of hexene and allylic alcohol bound by hydrogen peroxide, oxidation of ethylbenzene by dioxygen.
Polymer‐protected bimetallic clusters with various alloying structures
Authors: Toshima Naoki
Published: March 2011

Colloidal dispersions of polymer‐protected bimetallic cluster can be prepared by refluxing the alcoholic solutions of two kinds of metal ions in the presence of poly(N‐vinyl‐2‐pyrrolidone). The bimetallic clusters thus prepared had higher activity as catalysts than the corresponding monometallic clusters. The structure of bimetallic clusters, analyzed by an Extended X‐ray Absorption Fine Structure(EXAFS) technique as well as ultraviolet‐visible(Uv‐vis) absorption spectra, depends on the preparation method. Some of them have a special core‐shell structure. The order of the tendency to be a core is estimated to be Au>Pt>Pd>Rh. This order could be explained by the redox potential of the corresponding metal ion and the coordination ability of the metal to polymer.
Novel polymer‐supported chiral catalysts for asymmetric synthesis
Authors: Itsuno Shinichi , Kamahori Koichi , Watanabe Katsuhiro , Ito Koichi
Published: March 2011

Hydroxy amino acid monomers 3, 5 and amino acid monomers 10, 11 were prepared. Suspension polymerization of these chiral monomers with styrene and crosslinking agent afforded insoluble chiral polymers which were used as chiral ligands of the enantioselective Diels‐Alder reaction catalysts. A continuous flow system using polymeric catalyst was also successfully achieved in the same reaction.
Synthesis of rare‐earth metal‐containing polymers and their fluorescence properties
Authors: Zhou Yimin , Liu Rongqiang , Kong Deling , Sun Juntan
Published: March 2011

Four kinds of polymeric β‐diketone compounds, including poly(vinylbenzyldibenzoylmethane)(1), poly(vinylbenzylacetoacetone)(2), poly(vinylbenzyl‐2‐thenoyltrifluoroacetone)(3) and poly(p‐benzoylacetylstyrene)(4) were synthesized. And then polymeric β‐diketone‐europium(III), ‐terbium(III), ‐samarium(III), ‐dysprosium(III), ‐europium(III)‐gadolinium(III), ‐terbium(III)‐gadolinium(III), and ‐europium(III)‐terbium(III) chelates were also synthesized. The chelate structures were confirmed. The influence of the structure on the fluorescence properties was investigated. The fluorescence intensity of polymeric rare‐earth metal complexes is closely related to the ligand and metal content. Polymeric complexes possess a higher fluorescence stability than that of corresponding low‐molecular‐weight complexes.
Precise pariser‐parr‐pople molecular orbital calculations using new‐γ. A novel guiding principle for the design of functional materials
Authors: Tokita Sumio , Hiruta Kimihiro , Nishimoto Kichisuke
Published: March 2011

For precise Pariser‐Parr‐Pople molecular orbital (PPP MO) calculations, the values of the spectrochemical softness parameter k of a new two‐center electron repulsion integral new‐γ were evaluated based on an appropriate partial structure of polycyclic aromatic hydrocarbons (PAHs). The spectroactive aromatic sextet resonance system (ASRS) was defined as a spectroactive partial structure of a molecule. The calculated excitation energies of the p‐band of PAHs accurately reproduced the observed ones.
Computer design, synthesis and investigation of gradient‐modulus polymers
Authors: Askadskii Andrey , Goleneva Lidiya
Published: March 2011

Gradient‐modulus polymeric materials have been prepared, which show a continuous transition, within the same sample, from rubber to plastic without any junctions, joints, etc. These materials are elastic and have a modulus ranging from 4.5 to 2000 MPa. The properties of the materials were calculated before their synthesis. It was shown that a prerequisite of such materials is a network structure comprising rigid bulky crosslinked points and short flexible linking chains. Another prerequisite of such materials is the occurrence of microphase separation.