bluuebunny/crossref_metadata_2025 huggingface dataset:
Microbial aspects of the degradation of water‐soluble synthetic polymers
Authors: Kawai F.
Published: March 2011

This paper focuses on microbial aspects of degradation of synthetic polymers, especially of water‐soluble specialty polymers. The polymer structures analogous to natural polymers suggest biodegradability which originates from enzymes which do not discriminate between natural and synthetic polymers. Hydrolysis and oxidation are the primary processes for biodegradation. Assimilation rates are determined by the conversion of the polymer carbons into common metabolic products whether degradation is exogenous or endogenous. Biochemical mechanisms in the degradation of polyethers are summarized. Microbial symbiosis was involved in the degradation of a copolymer and the availability of symbiotic processes is suggested for the degradation of all copolymers. Transportability of PEG 20 000 through cell walls was suggested and a chemical process using hydrogen peroxide and ferric ions is proposed for the depolymerization of PEG with Mn more than 20 000 and its copolymers.
Environmental aspects of photodegradable plastics
Authors: Guillet James
Published: March 2011

During the latter half of this century the production of synthetic plastics and fibers has grown so that the total volume of plastics produced world–wide now exceeds that of steel. This paper is concerned with theoretical and experimental studies relating to the environmental consequences of such a rapid shift from a technology based primarily on agriculture, forestry and metallurgy to one based on chemical raw materials such as oil, coal and natural gas. It is shown that plastics and synthetic fibers have the lowest energy costs of all comparable materials and cause less environmental pollution in their production and fabrication. They are easily recycled when not contaminated with other materials and can be manufactured in photo‐or biodegradable modifications tailored to highly litter–prone applications. The topics covered include sections on resource costs and renewal, environmental considerations, the technology and role of photodegradable plastics, and experimental studies of the biodegradation of conventional and photodegradable polyethylene, polypropylene and poly(ethylene terephthalate).
New catalytic systems for the manufacture of poly(aspartic acid)
Authors: Ross Robert J. , Batzel Daniel A. , Meah Abdul Rahman , Kneller James F.
Published: March 2011

Aspartic acid (I), when heated to a temperature in excess of 180 °C, undergoes a solid‐state condensation polymerization to afford the useful polymeric intermediate known as poly(succinimide) (II). Treatment of poly(succinimide) with aqueous base, such as sodium hydroxide, affords sodium poly(α,β‐DL‐aspartate) (III) also known as thermal poly(aspartate) (TPA). Acid catalysts, such as phosphoric acid have been added to the aspartic acid to afford higher‐molecular‐weight poly(succinimide) than is obtained in the non‐catalyzed polymerization. Recently, new sulfur‐based catalysts have been disclosed for the polymerization of aspartic acid. The sulfur‐containing catalysts provide a route to highly biodegradable, low‐color poly(aspartate)s in the molecular weight range of 2 000 to 20 000. A comparison of biodegradability, molecular weight, and spectral characteristics of the poly(succinimide)s and poly(aspartate)s derived from the catalyzed and non‐catalyzed polymerizations is presented.
Light scattering and dielectric relaxation studies of glass forming liquids
Authors: Fischer Erhard W. , Patkowski Adam , Steffen Werner , Gläser Harald , Kanaya Toshiji , Reinhardt Lutz , Reiter Johannes , Thurn‐Albrecht Thomas , Stickel Franz‐Josef , Eckstein Eva
Published: March 2011

Extended Abstract: Glass forming organic liquids and polymers exhibit long range density fluctuations with correlation length ξ in the range of 10–300 nm at temperatures above Tg (1 ‐ 6). This follows from dynamic and static light scattering experiments revealing some unexpected features, which cannot be explained on the basis of conventional liquid state theories: (i) In static light scattering the intensity I(q → 0) is no longer proportional to the isothermal compressibility, (ii) This excess scattering Iexc shows a strong q‐dependence (q = (4π/Λ.)sin(θ/2)) corresponding to a correlation length ξ in the above mentioned range, (iii) The Landau‐Placzek ratio IRayleigh/2IBrillouin is much too high compared with the results of light scattering theories, (iv) In photon correlation spectroscopy a new ultraslow hydrodynamic mode (Γ ˜ q2) is detected with relaxation rates Γ about 10−6 to 10−9 lower than those of the α‐process at a given temperature.

In order to explain these observations, a two‐state fluid model is proposed, which starts from the coexistence of “liquid‐like” and “aperiodic solid‐like” regions within the liquids. Such ideas have been discussed many times before, so for example A.R. Ubbelohde (7) speculates about “anticrystalline” clusters in liquids. Molecular dynamics simulations of atomic liquids showed that long range orientational fluctuations appear upon supercooling (8). A preferred icosahedral ordering is observed (9) and the number of icosahedral clusters increases with decreasing temperature (10). In connection with the interpretation of the dynamics of supercooled liquids different “two‐state” models have been proposed (11 ‐ 15).

For the explanation of the light scattering results we propose that the molecules in the different dynamic states (“liquid” or “solid”) aggregate during annealing of the liquid at temperatures above Tg. Experiments showed that the equilibration times can be rather long (3 ‐ 5), but nevertheless the liquids exhibiting long range density fluctuations are in the state of lowest free energy. We claim that our observations are the first experimental proof of the existence of such different dynamic states, which have been discussed many times before. The extended secondary clusters can also be detected by ultra small angle X‐ray scattering.
Computational modelling of declination loops under shear flow
Authors: Lavine Marc S. , Windle Alan H.
Published: March 2011

Optical observations of sheared lyotropic and thermotropic liquid crystals have shown them to have a rich microstructure dominated by disclination loops and networks. In thermotropic liquid crystalline polymers it has been possible to freeze in the microstructures, which are then sectioned and analysed by optical and electron microscopy, to enable the identification of the predominant types of disclinations.

In this work a computational model is presented which simulates the development of texture in liquid crystalline materials. The model has been designed so that it is possible to study large localised distortions which are subjected to a flow field. In the aspect of the work reported here, simulations have been used to study the influence of simple shear on individual disclination loops placed in an otherwise undeformed sample. The subsequent deformation of the loop is shown to be dependent on the angle that the rotation vector of the loop makes with the vorticity direction.
Polymer crystallisation: Role of metastability and the confluence of thermodynamic and kinetic factors
Authors: Keller A. , Rastogi S. , Hikosaka M. H.
Published: March 2011

Consideration is given to the effect of size on the thermodynamic stability in situations where two or more phase variants compete in the course of a phase transformation. It is found that, pending on material parameters, a situation can arise where the stabilities of the competing phases invert with size. Such a size induced stability inversion can have a profound influence on phase development in general connecting also with the kinetics of the phase transformation. Specifically, this newly considered combination of interrelated thermodynamic (stability) and kinetic (rates) factors can provide an explanation for the frequently experienced dominance of metastable phases (the century old Ostwald Stage Rule). When applied to polymers, as in the example of polyethylene, it provides a new outlook for polymer crystallisation. Amongst others it creates a unified approach for the two, so far largely disconnected areas of chain folded and extended chain type crystallisation incorporating (not contradicting!) existing approaches within a widened framework.
Macromolecular aggregation: Complexation due to hydrogen bonding and hydrophobic association
Authors: Jiang Ming , Li Mei , Liu Lu , Xiang Maoliang , Zhu Lei
Published: March 2011

This paper reports the main results of the studies carried out in our laboratory on various kinds of polymer aggregation in aqueous and organic solutions. (1) In solutions of a polymer blend with controllable hydrogen bonding, a transition from individual polymer coils to intermolecular complex is observed as the hydrogen bonding interaction increases to a certain level. This is found to be a general phenomenon of polymer blends in which hydrogen bonding is adjustable. (2) A new kind of aggregation behavior of block ionomers based on SEBS is found and studied by fluorospectroscopy. The results explore that the block ionomer can form dispersion of hydrophobic aggregates in water stabilized by rare ionic groups. (3) Fluorocarbon‐containing PNIPAM in water establishes hydrophobic association. Fluorocarbon‐modified pyrene (PycoRf) is found to be qualified to serve as a fluorescent probe to monitor the association.
Failure modes in vapor‐deposited organic led's
Authors: Antoniadis Homer , Hueschen Mark R. , Miller Jeffrey N. , Moon Ronald L. , Roitman Daniel B. , Sheats James R.
Published: March 2011

A study of the main failure mechanisms in vacuum vapor‐deposited organic light‐emitting diodes (LED's) is presented. Three degradation modes were identified for a prototype bilayer ITO/TPD/Alq3/Mg/Ag device: a) formation and growth of black non‐emissive spots, b) abrupt ceasing of light emission associated with catastrophic failures caused by electrical shorts, and c) long term wearout associated with the decrease of quantum efficiency and luminance along with an increase in voltage, while the device is stressed under constant current.
Photoluminescence enhancement in organic microcavity structures
Authors: Dirr Siegfried , Wiese Stefan , Johannes Hans‐Hermann , Böhler Achim , Ammennann Dirk , Kowalsky Wolfgang
Published: March 2011

We have studied the photoluminescence properties of the metal chelates aluminum‐tris(8‐hydroxychinoline) (Alq3) and tris(4,4,4‐trifluoro‐1‐(2‐thienyl)‐1,3‐butanediono)‐1,10‐phenanthroline europium(III) (Eu(TTFA)3Phen) sandwiched between a planar Fabry‐Perot microcavity structure. A strong influence of the position of the emission thin film on the luminescence spectra has been observed. The emission intensity normal to the substrate surface is drastically enhanced by an order of a magnitude if the active layer is placed at the antinode of the standing wave in the cavity. In comparison to non‐resonant Alq3 structures, the FWHM of the spectrum is reduced from 100 nm to about 20 nm. We also show that the Eu(TTFA)3Phen luminescence is spacially directed due to the inherent linewidth of only Sum.
New luminescent polymers for leds and LECS
Authors: Hwang Do‐Hoon , Chuah Beng Sim , Li Xiao‐Chang , Kim Sung Tae , Moratti Stephen C. , Holmes Andrew B. , De Mello John C. , Friend Richard H.
Published: March 2011

Statistical copolymers 5 containing poly(2‐dimethyloctylsilyl‐1,4‐phenylenevinylene) (DMOS‐PPV) and poly[2‐methoxy‐5‐(2′‐ethylhexyloxy)‐1,4‐phenylenevinylene] (MEH‐PPV) have been synthesized using the dehydrohalogenation condensation route. The copolymers show a shift of photoluminescence maxima to longer wavelengths as the proportion of the MEH‐PV unit increases. This trend is accompanied by reduced efficiencies and lower turn‐on voltages in single layer electroluminescent devices. Light‐emitting electrochemical cells (LECs) have been prepared using a blend of DMOS‐PPV 1 with poly(ethylene oxide)/lithium triflate and the homopolymer poly[2‐methoxy‐5‐(triethoxymethoxy)‐1,4‐phenylene vinylene] (MTEM‐PPV) 9 with lithium triflate. In comparison with single‐layer devices which were fabricated using the homopolymers 1 and poly[2,5‐bis(triethoxymethoxy)‐1,4‐phenylene vinylene] (BTEM‐PPV) 10, the LEC devices showed lower turn‐on voltages.
Synthesis and characterization of a soluble blue light emitting alternating copolymer
Authors: Cho Hyun Nam , Kim Jai Kyeong , Kim Dong Young , Kim Chung Yup
Published: March 2011

An alternating copolymer with monomer units of fluorene and phenylenedivinylene was synthesized by reaction between n‐hexyl fluorene phosphonium salt and isophthalic aldehyde based on the Wittig reaction. The polymer solution in chloroform was made into a film with a very fine surface by spin‐casting on indium‐tin oxide (ITO) coated glass to fabricate a light emitting diode (LED) with an aluminum negative electrode. The optical absorption spectrum of the solid film shows a peak at 370 ran while the PL spectrum has the main peak at 560 nm with a secondary peak at 440 nm and the EL spectrum has a single peak at 560 nm showing the Stokes shift of 190 nm. The peak in the PL spectrum shifts to 420 nm with a vibronic structure at 440 nm on either dilution by chloroform or blending with polyvinylcarbazole (PVK). The emissive polymer bulk seemed to generate sites for excimers and molecular aggregates which were diminished on the dilution or blending. The peak in the EL spectrum also shifts to 440 nm on blending of 20% of the copolymer with PVK. Further dilution to 10% of the copolymer shifts the EL peak to 420 nm with the onset potential of 15 V and the highest quantum efficiency of 0.01% in this series. The concentrated channels were developed in the blends with severe phase separation to show a lower onset potential but poor quantum efficiency.
Coordination‐polymer films by reactive self‐assembly
Authors: Laurence D. , Iii Thomsen , Papadimitrakopoulos Fotios
Published: March 2011

A novel self‐assembly technique for the growth of insoluble and intractable thin organic films is presently reported. Bifunctional 8,8′‐dihydroxy‐5,5′‐biquinoline (bisquinoline) is reactively self‐assembled with diethyl zinc to form a linear coordination polymer. FTIR, UV/VIS spectroscopy, profilometry, and photoluminescence measurements were used to characterize these new multilayer films. The growth of these films on glass substrates was monitored by increasing absorbance at 396.6 nm using UV/VIS spectroscopy and by profilometry. FTIR spectroscopy indicated that the self‐assembled films are polymeric in nature. The reduction of end‐group hydroxyls and a significant red‐shift of the photoluminescence emission spectrum with respect to zinc bisquinoline powder was attributed to an increase in conjugation length.
Organic polymer leds with mobile and immobile ions
Authors: Schoo Herman F.M. , Demandt Rob C.J.E. , Vleggaar Jeroen J.M. , Liedenbaum Coen T.H.
Published: March 2011

The syntheses of partially conjugated alkoxy substituted Poly(p‐phenylenevinylene) (PPV) materials with tertiary amines and cationic species covalently bound to the polymer backbone are described. The amine/cationic species are introduced via a polymer analogous reaction of a functional alcohol and the chloro‐precursor polymer. Single layer, polymer light emitting diodes (PolyLEDs), prepared with the modified polymer materials show a strong ‘burn‐in’ effect, leading to very high electroluminescence (EL) quantum efficiencies especially with higher workfunction cathodes.
Thermal stability of organic electroluminescent devices fabricated using novel charge transporting materials
Authors: Tokito Shizuo , Tanaka Hiromitsu , Noda Koji , Okada Akane , Taga Yasunori
Published: March 2011

Novel hole and electron transporting materials have been synthesized to improve the thermal stability of organic electroluminescent (EL) devices. Molecular structures of such hole and electron transporting materials were designed based on triphenylamine (TPA) and oxadiazole (OXD) moieties, respectively. It has been found that the resulting materials have high glass transition temperatures (Tg) over 100°C and the vacuum‐deposited thin films are significantly thermally stable. For the two‐layer EL devices using the novel hole transporting materials and the typical emitting material, tris(8‐quinolinolato) aluminum, the thermal stability has been clearly seen to depend on the Tg of the hole transporting material; excellent thermal stability was achieved. For the three‐layer EL device using the novel electron transporting material, good emission efficiency and good stability were achieved. The electron transporting materials have been also applied to the polymeric system with polyvinylcarbazole matrix.
Studies of adhesion to molecularly engineered surfaces using contact mechanics methods
Authors: Kim Soojin , Choi Gun Young , Nezaj Jeff , Ulman Abraham , Fleischer Cathy
Published: March 2011

We synthesized a number of poly(dimethylsiloxane) (PDMS) polymers with different molecular weights, and prepared model PDMS networks with a systematic change of cross‐link density, and therefore elastic constant (K). Self‐adhesion studies of PDMS hemispheres using the JKR method—the contact mechanics of solids spreading their interfacial area under load—reveal that hysteresis which results from relaxation processes in the elastomer can be practically eliminated using stepwise loading and unloading protocols. The adhesion of crosslinked PDMS surfaces to self‐assembled monolayers with different chemical functionality was investigated. Interfacial H‐bonding was shown to be an important chemical interaction causing significant adhesion hysteresis. The number of H‐bonds between PDMS and silanol groups on SiO2/Si surfaces increased with time of the contact under a constant load, indicating pressure‐induced reorganization of the PDMS network near the interface. The interaction between PDMS and carboxylic acid groups showed somewhat smaller hysteresis which suggests weaker H‐bonding strength. The interaction between PDMS and functionalized biphenyl groups exhibited small hysteresis which is believed to be caused by dipolar interaction, whereas that between PDMS and nonpolar perfluorocarbon groups showed negligible hysteresis. The distinction in the behavior of the unloading data between H‐bonding related interaction and dipolar interaction seems to indicate the difference in the nature between non‐specific (van der Waals, dipolar) and specific (donor‐acceptor, H‐bond, acid‐base) interactions.
Absorption of ionic amphiphils by oppositely charged polyelectrolyte gels
Authors: Kabanov Victor A. , Zezin Alexander B. , Rogacheva Valentina B. , Khandurina Yulia V. , Novoskoltseva Olga A.
Published: March 2011

Slightly cross‐linked polyelectrolytes absorb oppositely charged surfactants in aqueous media. Transfer of amphiphilic ions from solution into the swollen network proceeds as a frontal heterogeneous cooperative reaction causing a collapse of the original polyelectrolyte gel. Small and wide angle X‐ray diffraction data show that electrostatic complex formed as a result of the reaction consists of lamellar type surfactant micelles embedded in a polyelectrolyte network. It is also shown that such complexes contain equimolar amount of surfactant ions and ionized polyelectrolyte units paired with amphiphil head groups. In other words a charged network is not able to bind surplus oppositely charged surfactant ions. However, it is still able to solubilize a substantial amount of a nonionized surfactant. Chemical structure of surfactants strongly affect internal structure of lamellae and stability of the complexes.
Polyelectrolyte adsorption and stabilization of silica‐suspensions
Authors: Bauer Doris , Killmann Erwin
Published: March 2011

The adsorption of cationic polyelectrolytes on colloidal silica‐particles is investigated. The polyelectrolytes poly(diallyl‐dimethyl‐ammoniumchloride) PDADMAC of different molar mass have been used. The adsorbed amount is influenced by the ionic strength and pH of the suspension and the molar mass of the macromolecule. The adsorption determines the zetapotential of the covered particles. The electrostatic interaction between the particles as well as the structure of the adsorbed polyelectrolytes play an important role in the stabilization and flocculation behaviour of the polyelectrolyte covered suspensions.
Polymers grafted from solid surfaces
Authors: Rühe Jürgen
Published: March 2011

Monolayers of polymer molecules were generated at the surface of a solid substrate in situ by using self‐assembled monolayers of initiator molecules. The layers were characterized by IR‐spectroscopy, surface plasmon resonance measurements, ellipsometry, X‐ray reflectometry, AFM and neutron reflectometry. Several novel techniques for the photolithographic patterning of the attached films are described. As a potential application for the attached layers the control of adhesion of biological cells to solid substrates is studied.
On the mechanism of adsorption of a cationic surfactant on quartz
Authors: Churaev N. V. , Sergeeva I. P. , Sobolev V. D.
Published: March 2011

Experimental data on surface charge of quartz in dependence on concentration of CTAB solution and pH were obtained using capillary electrokinetic method. The results are compared with the developed theory of the Langmuir‐type adsorption that takes Into account adsorption both on charged and noncharged surface centers. Computer optimization procedure results in adsorption potential values −15 kT and −11 kT, respectively. A ratio between surface concentrations of the centers was also estimated.
A study on the adhesion of anchoring groups to pigment surfaces
Authors: van Den Haak Henk J. W. , Schöps Matthias , Adler Hans‐Jürgen P. , Fietzek Christopher , Montagut Judit
Published: March 2011

A method is described for the comparison of the adhesion of anchoring groups to pigment or filler surfaces, using simple model compounds. Energies of adsorption and the amount of anchoring groups per gram of pigment can be estimated.
Electrochemical polymerization of functionalized thiophene derivatives for the immobilization of proteins
Authors: Welzel Hans‐Peter , Kossmehl Gerhard , Engelmann Gunnar , Neumann Barbara , Wollenberger Ulla , Scheller Frieder , Plieth Waldfried
Published: March 2011

The hydroxy group of 3‐(2‐hydroxyethyl)thiophene was protected as methyl ether 1 and as dimethyl tert‐butyl silyl ether 5 before anodic polymerization. The poly[3‐(2‐methoxyethyl)thiophene] 2 was prepared by electrochemical homopolymerization of 1. Ether cleavage was carried out in the polymer film 2 and the resulting poly [3‐(2‐hydroxyethyl)thiophene] (3) was activated with cyanogen bromide to immobilize alcohol dehydrogenase. Silylether 5 did not undergo homopolymerization but copolymerization of 5 with 3‐methylthiophene (4) was successful. After cleavage of the protecting group the resulting copolymer 7 was activated by cyanuric chloride, and chymotrypsin was immobilized. Electrocopolymerization of thiophene‐3‐acetic acid (8) and 3‐methylthiophene (4) under various conditions produces copolymer 9. By activation of the carboxylic groups with N,N'‐dicyclohexylcarbodiimide (DCC) lactate oxidase (LOD) was bond to the surface of the electrode to form a lactate sensor.
Interfacial tension in polymer blends
Authors: Luciani André , Champagne Michel F. , Utracki Leszek A.
Published: March 2011

Theoretical models of the interfacial tension coefficient in polymer blends, v12, were evaluated. A new working relation was derived that makes it possible to compute v12 from the chemical structure of two polymers. The calculations involve determination of the dispersive, polar and hydrogen‐bonding parts of the solubility parameter from the tabulated group and bond contributions. The computed values of v12 for 46 blends were found to follow the experimental ones with a reasonable scatter of ± 36%.

Next, the experimental methods of v12‐measurements were critically examined. Although many have been developed for low viscosity Newtonian fluids, most are irrelevant to industrial polymeric systems. For the present studies two were selected. Values of v12 were measured using the so‐called “capillary breakup method,” and a newly developed method based on the retraction rate of deformed drop.
Tem‐ and neutron reflection studies on surfaces and interfaces with block copolymers
Authors: Stark Bernhard , Scherble Jonas , Ganter Markus , Kressler Jörg , Stühn Bernd , Lauter Jochen
Published: March 2011

The behavior of block copolymers at various interfaces is studied by transmission electron microscopy and neutron reflection. A thin film of a symmetric diblock copolymer of styrene and methyl methacrylate forms layer structures when in contact with air and a random copolymer of styrene and acrylonitrile containing 35 wt% acrylonitrile. When the random copolymer has an acrylonitrile content of 25 wt%, a competition between layer formation and diffusion of disordered micelles takes place. Driving force for these processes are different interfacial tensions and a changing miscibility behavior as a function of acrylonitrile contents of the random copolymers. The ordering behavior of a symmetric diblock copolymer of deuterated styrene and isoprene in contact with poly(3,5‐dimethyl phenylene ether) is studied by neutron reflection. Polystyrene‐block‐poly(ethene‐co‐but‐1‐ene)‐block‐polystyrene with cylindrical PS microdomains shows an interfacial phase transition to lamellae near to the interface with different polymers. The morphological studies are in agreement with adhesion data obtained by peel tests on different bilayer specimens.
Neutron reflectivity studies of hot polymer melt interfaces
Authors: Hermes Helen E. , Bucknall David G. , Butler Simon A. , Higgins Julia S.
Published: March 2011

Neutron reflectivity data have been obtained using a specially designed cell that allows the investigation of the interfaces between polymers in the melt state. Systems which are semicrystalline at room temperature can be investigated for the first time. Example results from a polystyrene (PS)/ polyethylene (PE) interface (both with and without copolymer) and an isotactic polypropylene (PP)/ high density polyethylene interface are presented.
How green are petro‐polymers going to be?
Authors: Put Jos
Published: March 2011

The controversy between “petro‐polymers” and “green polymers” is a false one. Polymers synthesized by organisms, manipulated or not, are seen as green. Polymers based on cracker products, so called petro‐polymers, are considered to be environmentally unfriendly. Arguments used in favour of “natural” polymers are: biodegradability, renewable resources, recyclability, non waste producing etc. We think that several of these arguments are incorrect or irrelevant. Furthermore, we are convinced that petro‐polymers might move substantially towards a sustainable situation. It might seem strange, but the most important steps towards such a situation have to be made not in the field of petro‐polymers themselves but in the domain of energy supply.
Structure and mechanical properties of polysaccharides
Authors: Ross‐Murphy Simon B. , Wang Qi , Ellis Peter R.
Published: March 2011

This article serves both as a review of polysaccharides as gelling and thickening agents and as an introduction to polysaccharides, other than starch and cellulose, their source and extraction, and how molecular detail is reflected in their macromolecular and supramolecular properties. The whole is summarised for workers in the synthetic polymer area interested in new “green” polymers. We also introduce results for a new polysaccharide extracted from a Nigerian tree pod, and describe details of its structural and physicochemical characterisation including light scattering and rheological measurements.
Starch alkanoates as models for thermoplastic polysaccharides
Authors: Pellegrini Claudio , Tomka Ivan
Published: March 2011

The low degree of internal molecular mobility of stiff polysaccharide chains prevent any thermal transition in the temperature range of their chemical stability. Substituted starches were synthesised to find the structural range, i.e. the necessary amount and length of mobile side chains which support the molecule with high enough level of internal degrees of freedom. Esterification and transesterification with hydroxy alkanoates, their polymers and lactones were used. The reaction was best catalysed with strong delocalised bases. The thermal properties of these model substances were characterised.
Starch ‐ polyvinylalcohol ‐ acetal: A watersoluble film
Authors: Keilbach Andreas , Tomka Ivan
Published: March 2011

To ensure more comfort, dosage units of active ingredients may be packed in water soluble film prior to application. In the mean time plasticised polyvinylalcohol (PVAL), with limited metabolitic degradability in common water epuration units, is used for present purpose. In this work we found that the reducing chain ends of degraded starch molecules form semi acetals with the hydroxyl moieties of (PVAL). Reaction conditions could be selected for processing in a twin screw extruder. Due to replacement of around 50% of the polyvinylalcohol by starch the production costs are significantly lower than that of pure PVAL‐films. The acetal films show better mechanical properties, seal easier, dissolve faster in water and mineralise at lower temperatures if compared with pure PVAL.
Polymers from pine gum components: Radical and coordination homo and copolymerization of pinenes
Authors: Ramos Ana Maria , Lobo Luís S. , Bordado João M.
Published: March 2011

The present work is aimed at studying the reactivity of α‐ and β‐pinenes in radical polymerization. The pinene homopolymers obtained were oligomers, showing both isomers similar reactivities. In order to achieve products of higher molecular weight, the radical copolymerization of α‐ and β‐pinene with methyl methacrylate and styrene was performed, giving rise to polymers with M̄w varying from 11 500 to 53 000. In radical copolymerization α‐pinene showed to be more reactive than β‐pinene. All the radical reactions performed were carried out with a Ziegler‐Natta catalyst, TiCl4/Et3Al, and with Et3Al. Under the conditions tested, β‐pinene did not undergo any polymerization reaction and the cocatalyst showed a pronounced catalytic effect. The coordination polymers obtained at 5 h had chain lenghts of the same order of magnitude of the corresponding radical copolymers obtained at 50 h, although for much lower overall conversion.
Investigations on homopolymerization and copolymerization of phenylacetylene and 1‐hexyne by iron‐based ziegler‐natta catalyst systems
Authors: Duc Sandrine , Petit Alain
Published: March 2011

Homopolymerization and copolymerization of phenylacetylene (PA) and hex‐1‐yne (HX) were performed in the presence of two iron‐based catalysts having various ligands: an organic salt, iron tripropionate [Fe(prop)3] and a complex, iron triacetylacetonate [Fe(acac)3], both in combination with the triethylaluminum (AlEt3). The geometric structures of the resulting monosubstituted polyacetylene samples were investigated by 1H‐NMR, 13C‐NMR and IR spectroscopic techniques. The number‐average molecular weights were also determined. The compositions of the PA‐HX copolymers were obtained by 1H‐NMR analysis and the monomer reactivity ratios were calculated from these values using the Kelen‐Tüdös method and a nonlinear least squares curve‐fitting procedure. The proportions of cis and trans structural units in polyalkynes and the relative reactivities of two monomers PA and HX during the copolymerization were found to be strongly associated with the nature of the initiating system.
Polyfunctional polyisobutenes as building blocks for amphiphilic graft polymers
Authors: Grasmüller Martin , Rueda‐Sanchez Juan C. , Voit Brigitte I. , Nuyken Oskar
Published: March 2011

Polyfunctional polyisobutenes (PIB) have been synthesized by cationic copolymerization of isobutene and chloromethylstyrene. Their potential applications with focus on their use as macroinitiators (MI) for oxazoline polymerization were discussed. The “grafting from” reaction led to tailor‐made graft copolymers with various backbones and adjustable graft arm length. Graft copolymers with hydrophobic PIB backbone and poly(2‐methyloxazoline) graft arms have unusual viscosity properties due to their amphiphilic character and show aggregate formation.
Adhesive liquid‐crystalline polymers
Authors: Nieuwhof René P. , Marcelis Antonius T. M. , Sudhölter Ernst J.R. , van Der Wielen Maarten W.J. , Cohen Stuart Martien A. , Fleer Gerard J.
Published: March 2011

The synthesis and characterization of liquid‐crystalline polymers with possible good adhesive properties is reported. These polymers are prepared by alternating copolymerization of maleic anhydride and mesogenic alkenes. The spacer length m is varied (m = 2, 3, 4, 6, 8 and 9) and methoxybiphenyl is used as the mesogenic group. The glass transition temperature decreases and the isotropization temperature increases with spacer length. Depending on the spacer length and temperature, SB and SAd mesophases can be observed. After annealing, spin‐coated films of these polymers show very regular layered structures with a layer spacing similar to that in the bulk.
Electrospinning of ultra‐thin polymer fibers
Authors: Jaeger Raimund , Bergshoef Michel M. , Batlle Cristina Martín I. , Schönherr Holger , Julius Vancso G.
Published: March 2011

The electrospinning technique was used to spin ultra‐thin fibers from several polymer/solvent systems. The diameter of the electrospun fibers ranged from 16 nm to 2 μm. The morphology of these fibers was investigated with an atomic force microscope (AFM) and an optical microscope. Polyethylene oxide) (PEO) dissolved in water or chloroform was studied in greater detail. PEO fibers spun from aqueous solution show a “beads on a string” morphology. An AFM study showed that the surface of these fibers is highly ordered. The “beads on a string” morphology can be avoided if PEO is spun from solution in chloroform; the resulting fibers show a lamellar morphology. Polyvinylalcohol (PVA) dissolved in water and cellulose acetate dissolved in acetone were additional polymer/solvent systems which were investigated. Furthermore, the electrospinning process was studied: different experimental lay‐outs were tested, electrostatic fields were simulated, and voltage ‐ current characteristics of the electrospinning process were recorded.
Effects of recycling on mechanical and thermal properties of polystyrene
Authors: Djidjelli H. , Benachour D.
Published: March 2011

A commercial Polystyrene (Mw = 2.5 105, MFI =14.80) was extruded repeatedly from one to eight times at 190 °C. The effects of extrusion process on physical and chemical properties of polystyrene were investigated using: ‐Average molecular weight

—Izod Impact strength;

—Thermal properties (TGA, DTA).

The results showed that processing of polystyrene leads to degradation. In fact, a decrease of 23% in the average molecular weight was observed for the 8th cycle sample and a reduction in impact strength by 34% was also noticed for the 4th cycle sample.
Polypropylene, modified with some oligoesters
Authors: Gorbunova Irina YU. , Kerber Michail L. , Vladimirova Svetlana I. , Musleh Reem R. , N. Avdeev Nickolay
Published: March 2011

Miscibility of polypropylene with some oligoesters was evaluated by optical wedge interference microscopy. Mechanical, thermal, rheological and relaxation properties were studied. Compatibility between the polymers and modifying agents was shown to have a marked effect on stress‐strain properties as well as on the structure and melting characteristics of the modified polymers.
Abiotic and biotic degradation of aliphatic polyesters from “petro” versus “green” resources
Authors: Karlsson Sigbritt , Albertsson Ann‐Christine
Published: March 2011

Aliphatic polyesters are degradable by abiotic and/or biotic hydrolysis. The accessibility of a polymer to degradative attack by living organisms is not dependent on its origin, but on its molecular composition and architecture. Synthetic polymers with intermittent ester linkage (e.g. polyesters, polyurethanes etc.) are accessible to biodegradative attack of esterase. On the other hand aliphatic polyesters are also quickly degraded by a pure abiotic hydrolysis. The results from abiotic and biotic hydrolyses of polycaprolactone (PCL) (from “petro” resource), poly(L‐lactide) (PLLA) and polyhydroxyalkanoates (PHA) (from “green” resources) are presented and discussed with the respect to rate of degradation, molecular weight changes and degradation product pattern. For the environmental consequences, the type of formed degradation products are of importance and not the origin of the polymer.
Synthetic and natural polymers as drug carriers for tuberculosis treatment
Authors: Batyrbekov Erkesh O. , Iskakov Rinat , Zhubanov Bulat A.
Published: March 2011

Drug forms based polymer carriers of prolong action were created for toxicologic effect of drug to be reduced in spite of long treatment of diseases. In present work a number of synthesis and natural polymers have been studied as carriers of antituberculous drugs for controlled delivery application. Following as drugs as isoniazid and ethionamide were incorporated into polymeric matrix (segmented polyurethanes, polyvinyl alcohol) and chemically bound with the polymer chain by covalent or electrostatic forces (aldehyde‐ and carboxymethylderivatives of polysaccharides). Biodegradation of polymeric systems and the release of drugs were studied by various physico‐chemical methods. It was shown that the drug release depends of method of the immobilization, type of the drug/polymer bonding, drug loading. The bacteriostatic activity of obtained systems was determined. The possibility of tuberculosis treatment was proved in experiments of animals.
Solid state interchain transesterification reactions in macromolecules
Authors: Economy J. , Schneggenburger L. A.
Published: March 2011

Interchain transesterification reactions (ITR) play an important role in high temperature synthesis of most linear polyesters. For example, polyethylene terephthalate (PET) is prepared commercially by heating and distillation of ethylene glycol from a glycol capped oligomer of PET. In this paper, the potential importance of ITR to effect a much wider range of reactions and process is examined. For example, the ability to control the sequence distribution in linear copolyesters is described. In particular, it is shown that one can induce a random sequence distribution in copolyesters by ITR or, conversely, develop an ordered sequence from a random copolyester again by ITR. In one family of liquid crystalline copolyesters an unusual competition between ordering and a thermal Fries rearrangement is described. A whole new family of crosslinked copolyesters has been developed based on this knowledge of ITR. Solid state processing of cured copolyesters into finished articles by ITR has also been demonstrated. These crosslinked copolyesters can be depolymerized back to the starting oligomers by a reverse ITR, providing for the first time a recyclable thermosetting resin.
Synthesis of hyperbranched aromatic polyamides by direct polycondensation
Authors: Russoy Saverio , Boulares Alya , Mariani Alberto
Published: March 2011

Some hyperbranched aromatic polyamides have been synthesized by direct polycondensation using the modified Higashi's method. Structures of the above polymers have been realized taking in proper account the analogies with amide group sequences of poly(p‐phenyleneterephthalamide) (PPDT) and poly(p‐benzamide) (PBA). Therefore, AB2‐ type monomers as well as suitable combinations of different bi‐ and trifunctional reactants (AA + B3) (e.g., p‐phenylenediamine + trimesic acid or other trifunctional acids) have been considered. For the latter systems, network formation has been minimized. In the present paper, our results on their direct polyamidation together with some preliminary characterization data on the resultant hyperbranched aramids are given.
Macrocyclic polymerization ‐ a new approach to molecular engineering
Authors: Kricheldorf Hans R. , Lee Soo‐Ran , Eggerstedt Sven , Hauser Karsten
Published: March 2011

2,2‐Dibutyl‐2‐stanna‐1,3‐dioxacycloalkanes were used as cyclic initiators for the ring‐opening polymerization of various lactons. This method exclusively yielded series of macrocyclic polylactones without any competition with linear polymers. Under optimized reaction conditions these macrocyclic polymerizations obey the pattern of “living polymerizations”. The living chain ends allow the syntheses of macrocyclic blockcopolymers. The macrocyclic polylactones react with carboxylic acid chlorides by ring‐opening yielding telechelic oligo or polylactones. Furthermore, the tin containing macrocyclic polylactones can be used as difunctional “monomers” for polycondensations with dicarboxylic acid dichlorides.
The synthesis of mesogenic polymers provoked by molecular mobility. polysiloxanarylenes
Authors: Skorokhodov Serguei
Published: March 2011

An approach to the synthesis of potentially thermotropic liquid crystalline polymers based on parallel investigation of their molecular mobility was realized. The initial idea was provoked by the observation that there exists some correspondence of molecular mobility data and the ability of a polymer to form a liquid crystalline phase. Previously this phenomenon was demonstrated on the example of a series of thermotropic main chain polymers with flexible dimethylsiloxane spacers of variable length. The relation between the structure of the main chain and local molecular mobility of different fragments was investigated in a series of regular polysiloxane‐silarylenes containing rigid aromatic sequences. Molecular mobility was studied by dielectric spectroscopy in solution and in solid state. The structure of the main chain has been changed by variation of the repeated fragments' length, substituents and joint groups. The data of molecular mobility and their conformity with the chain structure were used for directed synthetic search of desired mesogenic polymers.
New aspects in chemistry and characterization of poly(ethylene oxide) hydrogels
Authors: Kazanskii Konstantin S.
Published: March 2011

To extend the variability of poly(ethylene oxide) (PEO) hydrogels in their swelling behaviour, ability to bind various subjects, and possible applications, some new synthetic approaches have been elaborated recently: (i) PEO networks with ionic and reactive groups were prepared by the reaction of P‐OH groups of poly(oligoethylene glycol phosphate)s with diepoxide. The swelling degree of these hydrogels is strongly affected by salts, what is typical of polyelectrolyte networks. The structure parameters of the network evaluated from the swelling data are discussed.

(ii) A series of hydrogels with controlled structure was obtained by radical polymerization of methacrylate PEO macromonomers of various molecular weights and average functionality (0.99–1.85) in aqueous media. The networks prepared are characterized by means of elastic modulus and swelling pressure measurements as well as with the help of microparticles of liquid‐crystalline dispersion of DNA as probes highly sensitive to the network structure and state.
Structural influences on the properties of aromatic polyamidines
Authors: Böhme Frank , Kunert Christoph , Klinger Christian , Komber Hartmut
Published: March 2011

Polyamidines with both nitrogens in the main chain (‐X‐NH‐CR=N‐) were obtained by polycondensation of diamines with different orthoesters. The thermal properties could be tailored by the choice of diamine and orthoester. Quantitative formation of a cyclic trimer could be observed when 2,6‐diamino‐pyridine was converted with triethyl orthoformate. 1H, 13C and 15N NMR spectroscopic investigations in solution and in solid state showed that the configuration of the amidine group was strongly dependent on the residue R. In polyformamidines, strong interactions caused by hydrogen bonds could be evidenced.
Novel branched blockcopolymers from poly(vinylpyridine) by chromium allyl compounds
Authors: Novakov Petar P. , Kuckling Dirk , Fedorova Ljubov , Adler P. Hans‐Juergen
Published: March 2011

Novel branched blockcopolymers from polyvinylpyridine are formed by chromium allyl compounds. Our present work shows results for the homopolymerization of vinylpiridine (VP), dimethylacrylamide (DMAA), tert ‐ butylacrylate (t ‐ BA) as well as the graftcopolymerization of poly(vinylpyridine) (PVP), using tris (π ‐ allyl) chromium (TPC) as initiator. PVP activated by TPC was used for grafting with DMAA ‐ “grafting from”. On the other hand living PDMAA polymerized by TPC, was able to react with PVP chain ‐ “grafting onto”.
Acid‐catalyzed reactions in polyimide synthesis
Authors: Kuznetsov Alexander A. , Tsegelskaya Anna Yu. , Belov Michael Yu. , Berendyaev Vladimir I. , Lavrov Sergey V. , Semenova Galina K. , Izyumnikov Anatoly L. , Kozlova Nina V. , Kotov Boris V.
Published: March 2011

Melts of aromatic carboxylic acids are found to be excellent reaction media for 1‐pot high molecular weight polyimide synthesis from diamines and tetracarboxylic acid dianhydrides. No reversible reaction of polyamic acids (PAA) formation was observed. The effect of the reactivity equalization was observed for low‐ and high reactive diamines in acid media. The intrinsic acid catalysis of the imidization reaction was shown to take place also in polycyclization of PAA in concentrated solutions in amic solvents. It is found that the dependence of relative imidization rate (% conv./min) vs. AA/N‐MP ratio for model low molecular and oligomeric amic acids (AA) in N‐MP at 140–150°C possesses a sharp maximum near the molar ratio 1:1, the imidization rate at the point of the maximum being an order of magnitude higher than that for diluted solutions. A scheme is proposed which includes the opportunity of two reaction channels to occur: A usual one (I) and a catalytic one (II). In diluted solutions and in solid phase experiments with easy evacuation of volatile products, the role of catalytic channel II is low. To the contrary, in high concentrated solutions or in solid phase experiments under the conditions exluding volatile products evacuation, the catalytic channel becomes the key one. It is proposed that the catalytic reaction proceeds via the common acid catalysis mechanism, the solvent and water playing the role of co‐catalysts, probably through the mechanism of ionic dissociation of AA or hydrogen‐ bound complex AA‐solvent. It is shown that the water released in the course of solid phase imidization of phtalamic acid at 140°C under the conditions where vaporization is impossible causes a sharp autocatalytic effect after initial 20%‐conversion period to obtain entirely imidizied product.
Controlled polymerization of cyclic esters. structure of initiators and of active species related to the selectivity of initiation and propagation
Authors: Penczek Stanislaw , Duda Andrzej , Libiszowski Jan
Published: March 2011

This paper reviews mostly the already published work of our own, complemented with some new data and related to the control (i.e. selectivity) in the anionic and covalent (pseudoanionic) polymerization of cyclic esters. Ionic and covalent growing species are briefly compared in terms of their susceptibility to undergo side reactions. Then, structures of covalent initiators (mostly multivalent metal alkoxides) are discussed from the view point of their behavior in initiation and formation of active species. R2AlOR', (RO)3Al, and other metal alkoxides are discussed.
Chemical modification of polymeric hydrocarbons
Authors: Braun Dietrich , Hellmann Goetz P.
Published: March 2011

Although polymeric hydrocarbons (PCH) carry no functions, they can be modified in many ways. Unsaturated PCH undergo addition reactions as hydrogenation, halogenation, epoxidation and thiol addition. Saturated PCH can be substituted with various functions, notably halogen and chlorosulfonyl groups. All PCH can be modified, by a grafting mechanism, with functional monomers as maleic anhydride. Some modified PCH play a major role in multiphase systems as blends, rubber‐modified thermoplastics and thermoplastic elastomers. Attractive grafting procedures involve in‐situ grafting in PCH/monomer solutions and during reactive blending processes.