bluuebunny/crossref_metadata_2025 huggingface dataset:
Stereoregular polymerization of methyl methacrylate initiated by dialkylmagnesium‐quaternary ammonium salt adducts
Authors: Novakov Christo P. , Tsvetanov Christo B.
Published: March 2011

The anionic polymerization of methyl methacrylate was carried out in the presence of Bu2Mg/quaternary ammonium salts in toluene at 0°C. It was found that the bulkiness and shape of the salt strongly affect the polydispersity and tacticity of the resulting polymers. Molecular weight distribution is in the range 1.3 w/Mn 4.7.>Tetrahexylammonium chloride causes the most drastic change in the tacticity. The structure of R4MNX, as well as the nature of the metal and the t‐BuOLi ligands produce a radical effect on the polymer properties. These initiator components perform their role by changing the microenvironment of the ligated and aggregated growing chains. The results clearly reveal the great potential of the mixed associate or mixed base as strong stereospecific initiator systems.
Ylide mediated polymerization of methacrylates and acrylates in the presence of tetraphenylphosphonium cation 3
Authors: Zagala Angela P. , Dimov Dimo , Hogen‐Esch Thieo E.
Published: March 2011

Triphenylmethide tetraphenylphosphonium (TPM, TPP) or methylisobutyrate tetraphenylphosphonium (MIB, TPP) formed by ion exchange reactions of TPP chloride(TPPCl) with the TPM or MB potassium salts in THF, initiate the living polymerization of MMA producing PMMA's with narrow MW distributions (below 1.3) at ambient temperatures.
Optically active polymers of 3‐alkylmalic acids: Contribution of the bioconversion for diversifying the chiral precursors
Authors: Bear Marie‐Maud , Langlois Valérie , Masure Michèle , Guerin Philippe
Published: March 2011

The need for new optically active monomers and polymers is conducive to the setting up of stereospecific synthesis routes starting from chiral precursors. The biomass can be considered as a major source for extracting such biomolecules aimed at chemoenzymatic transformation and further polymerization. Due to its versatility, ß‐methylaspartate ammonia‐lyase, from cell‐free extracts of Clostridium tetanomorphum, has been used in the bioconversion of alkylfumarates into optically active pure 3‐alkylaspartic acids with alkyl=methyl, ethyl, isopropyl. These amino acids have been transformed in several steps into optically active benzyl 3‐alkylmalolactonates leading to semi‐crystalline polyesters. 3‐Methylaspartic acid includes two chiral centers and the racemic compound containing the four stereoisomers can be prepared by a multiple step synthesis. The ability of ß‐methylaspartase to catalyse both syn‐ and anti‐elimination of ammonia from natural 3‐methylaspartic acid has been expressed to retain one stereoisomer and this bioconversion is a preparative method for obtaining unnatural stereoisomers. Moreover, the catalytic hydrogenolysis of the benzyl α,ß‐substituted ß‐lactone yields stable 3‐alkylmalolactonic acid which can be coupled with functional alcohols and copolymerized. At last the introduction of (2S)‐3,3‐dimethyl‐2‐butanol, using Rhodotorula glutinis as microorganism in a biological synthesis step, as chiral ester pendant group, has conducted to optically active polyesters with very high melting transition temperatures. The combination of bioconversion and chemical synthesis is a very useful tool for building hydrolyzable functionalized polyesters required for temporary applications.
Copolyethers with controlled structure: Mechanism of formation and microstructure
Authors: Bednarek Melania , Kubisa Przemyslaw
Published: March 2011

Cationic copolymerization of 3‐membered cyclic ethers (oxiranes) with 5‐membered cyclic ether (tetrahydrofuran) leads to linear copolyethers containing significant amount of cyclic fraction. When the copolymerization is conducted in the presence of diols, telechelic copolymers are formed by the process in which oxirane is incorporated into copolymer irreversibly by Activated Monomer mechanism, while tetrahydrofuran is incorporated reversibly by Active Chain End mechanism. Thus both kinetic and thermodynamic factors can be used to control the rate of the incorporation of comonomers. Studies of the kinetics of the competing reactions leading to formation of copolymer, studies of copolymer microstructure by 13C‐NMR and analysis of the composition of the cyclic fraction, led to the correlation between the copolymer microstructure and the amount of cyclic fraction formed. The dependence of the cyclic fraction content on the reaction conditions was therefore explained.
Cationic polymerization of aliphatic cyclocarbonates
Authors: Kricheldorf Hans R. , Weegen‐Schulz Bettina , Jenssen Jörg
Published: March 2011

Numerous polymerizations of trimethylene carbonate (TMC) and neo‐pentylene carbonate (NPC) were conducted in solution using methyl triflate as initiator. The polymerization mechanism was elucidated and rapid backbiting degradation along with the formation of ether groups was detected. When strong Lewis acids such as BF3, SnCl4 or SnBn4 were used as initiators, much higher molecular weights were obtained, but the resulting polycarbonates still contained ether groups. BuSnCl3 was found to be the most useful initiator yielding high molecular weight polycarbonates free of ether groups. However, in this case it is not clear, if a cationic mechanism or a coordination‐insertion mechanism is involved.
Initiation of cationic polymerization by photoinduced electron transfer
Authors: Yagci Yusuf
Published: March 2011

The objective of this paper is to discuss: (i) the general approaches to the initiation of cationic polymerization by photinduced electron transfer reactions (ii) the use of photoinduced electron transfer reactions for block copolymer synthesis. For the first, it is concluded that three general methods are currently available which involve reduction of onium salts by (a) photogenerated radicals, (b) photoexcited sensitizers or (c) electron donor compounds in charge transfer complexes. According to this view, a variety of initiating systems are discussed. For the second, recent developments on the application of photoinduced electron transfer reactions to the synthesis of block copolymer of monomers polymerizable with different mechanisms are presented.
Stepwise pyrolysis for recycling of plastic mixtures
Authors: Bockhorn Henning , Hornung Andreas , Hornung Ursel
Published: March 2011

For chemical recycling of plastic refuses a cascade of cycled‐spheres reactors has been developed combining separation and decomposition of polymer mixtures by stepwise pyrolysis at moderate temperatures. In low‐temperature pyrolysis, mixtures of poly(vinyl chloride), polystyrene and polyethylene or polystyrene, polyamide 6 and polyethylene have been separated into hydrogen chloride, styrene and polyamide 6 and aliphatic compounds from polyethylene decomposition. Compared with the low‐temperature pyrolysis of the single components, some interactions between the polymers are found when pyrolyzing mixtures. Some mechanistic aspects of these interactions are discussed.
Energy recovery
Authors: Akehata Takashi
Published: March 2011

Incinerators in use, power‐generating incinerators and pollution‐prevention methods in energy recovery from waste incineration are briefly reviewed. Results of a recent energy recovery experiment under real operating conditions are described: The addition of waste plastic to municipal solid waste brought about more stable combustion and no increase in the concentrations of dioxins. It is remarked that energy recovery through incineration is probably the best currently available means of disposal for plastics which are too difficult to recycle.
Several hypotheses and regularities in the chemistry of highly organized substances
Authors: Aleskowskii Valentin
Published: March 2011

It was found that level of structural substance organization, amount of embodied information, and consequently, substance properties are determined by the degree of the substance polyatomicity. This substantiates the fact that both covalent and noncovalent supermolecular individuals, which are the matter of the chemistry of highly organized compounds, fulfil the same general chemical but different specific regularities. Among the former there is extended Prust's law, which was re‐established by the fact of production and identification of solids with the constant composition. It was also found that formation of any individuals is due to production and realization of a certain amount of information sufficient for their structural organization. Chemical modeling of biosynthesis was chosen as the common approach for developing the processes of production and realization of information. It was shown that well‐known processes of chemical buildup (CB) and molecular self‐assembling (MSA) are those chemical models. The application of announced regularities has opened up a new perspective to create chemical‐information technology (CIT), allowing us to produce material resources making no perturbations in the planet ecosystem.
Augmented cylindrical wave method in the theory of electronic structure of quantum nanowires
Authors: D'yachkov Pavel N. , Kepp Oleg M. , Nikolaev Alexander V.
Published: March 2011

A computational method for the band structure of nanowires having approximately cylindrical symmetry is developed. The effective one‐electron potential is supposed to have spherical symmetry in the region of the atomic centres and is assumed to be constant in the interstitial region. The corresponding electronic density is supposed to be localised inside the region of cylindrical shape. The base wave functions are obtained by sewing together solutions of the Schrödinger equation for an electron in the empty cylinder (cylindrical waves) with spherically symmetrical solutions for the muffin‐tin spheres. Under the condition of the continuity of the base functions and their first derivatives overlap integrals and Hamiltonian matrix elements are obtained. Dispersion curves and electronic densities of states for chains of transition metals and those of nanowires from metals from K to Zn are calculated.
Study of the DNA packing caused by charged compounds of different nature in solution
Authors: Kasyanenko Nina A. , Zanina Anna V. , Plotnikova Ludmila V. , Simonenkov Andrei A. , Defrenne Stephanie , Nazarova Olga V. , Panarin Evgenii F.
Published: March 2011

A comparative study of DNA interaction with different counterions in solution has been conducted by the following methods: flow birefringence (FB), low‐gradient viscometry, circular dichroism (CD), and UV‐spectroscopy. The influence of counterions on the persistence length and polyelectrolyte swelling of DNA has been investigated. The process of DNA packing during the interaction with trivalent ions in solution has been studied, as well as the influence of Mn2+ on the binding of trivalent ions with DNA.
Cluster carbonyls of Os, Fe and Fe‐Rh on oxide supports: Synthesis and properties
Authors: Kuznetsov Boris N. , Kovalchuk Vladimir I. , Chesnokov Nikolai V. , Mikova Nadezhda M. , Naimushina Lilia V.
Published: March 2011

Surface nano‐size structures have been obtained by supporting on oxide supports (SiO2, MgO, Al2O3) some cluster carbonyls of Os, Fe, Fe‐Rh and by their following thermal conversions. Surface species were characterized by IR‐spectroscopy, high‐resolution TEM, XPS, Mössbauer spectroscopy and temperature‐programmed desorption technique. Their catalytic properties was studied in CO hydrogenation reaction.
Organized molecular assemblies: Creation and investigation of their functional properties
Authors: Repinsky Sergey M.
Published: March 2011

One of the most important problems of modern chemistry, both preparative and theoretical one, is the creation of organized atomic ‐ molecular assemblies i.e., atoms and molecules bound in a definite manner and interacting with each other, as a jointly, they become able to behave like an assembly, a single mechanism, to perform some functions, for example, to recognize separate molecules of environment (receptors), to transform an electromagnetic signal to electric field (photosynthetic), to memorize (memory cell), catalyze function and others.

The chemistry of preceding period had been developing as the science of properties and transformations of individual compounds and substances. At present the progress in the notion of the nature of chemical bonds, a new level of understanding of the chemical reactions mechanism, the knowledge of the regularities of nonstationary states in reactive media and the data on the at processes interfaces have determined the up to day problem of organized molecular assemblies with a required functionality.

Thermal oxidation of silicon crystals which is the key process in the technology of integral circuits production can be represented, in its main features, by the mechanism of semiconductor dissolving in the condensed phase. A characteristic feature of silicon oxidation is that the silicon activation energy of the limiting stage is lower than that of the formation of gas ‐ phase monoxide, difference being the energy of siloxane net reorganization in silicon dioxide. The analysis shows that within the row of possible systems semiconductor ‐ dielectric, it is silicon ‐ silicon dioxide that is distinguished by a maximum self ‐ organizing effect. This is one of the main reasons why only silicon could be chosen among large number of semiconductor substances for use in the technology of integral circuits.

A molecular system of amphiphilic long ‐ chain molecules, obtained according to the Langmuir ‐ Blodgett method is an example of simplest assembly on the basis of which the elements of gas sensors can be prepared, as well as the systems of quantum dots, the objects of the low ‐ dimension physics.

We have investigated assemblies constructed from multimolecular compositions using the Langmuir ‐ Blodgett technique and thin ‐ layer systems based on glassy and amorphous silica films with fragments of organic molecules introduced into the matrix.

Molecular engineering is a new level of the modern preparative chemistry; moreover, it is a system of concepts introducing a new culture in technology. In this sense, it is most important to realize the evolution principle in the strategy of science research.
Optimisation of photo‐induced geometric isomerisation of azobenzene derivatives in dye‐doped polymer films for enhanced photo‐induced poling
Authors: Mitchell G. R. , King N. R.
Published: March 2011

Photo‐induced geometric isomerisation of azobenzene based chromophores can be utilised in a variety of molecular control procedures including photo‐induced poling. In such processes additional mobility is imparted to chromophores trapped in a glassy matrix through the photo‐induced trans‐cis‐trans cycle. We show that by using selected narrow wavelength bands of light to induce the isomerisation cycle during photo‐induced poling, enhanced levels of polar order can be obtained in comparison to those obtained with monochromatic light. We attribute this to an increase in the fraction of chromophores which undergo isomerisation via an inversion mechanism. As a result, a higher proportion of the chromophores are able to participate in the photo‐induced poling process since the free volume for isomerisation is reduced from that required for the rotation mechanism.
Complex formation through heterogeneous nucleation of thermoreversible gelation
Authors: Guenet Jean‐Michel , Lopez Daniel
Published: March 2011

The preparation method and the molecular structure of a composite material consisting of a ternary system polymer/bicoppercomplex/solvent are presented. The properties of each binary system are exposed first. The polymer solutions produce thermoreversible gels while the bicopper organic complex forms a randomly‐dispersed, self‐assembling structure in organic solvents. It is shown that, in a common solvent, the bicopper complex acts as a nucleation agent for the gelation of the polymer (heterogeneous nucleation). As a result, bicopper complex filaments are encapsulated in a polymer matrix.
NMR approach to kinetics of polymer ordering in polyacrylonitrile solutions and acrylonitrile‐sodium methallylsulfonate copolymer solutions: Solution‐concentration and polymer‐tacticity effect
Authors: Margulies Monique Marie , Viallat Annie , Addad Jean‐Pierre Cohen
Published: March 2011

Partial crystallinity of polyacrylonitrile and acrylonitrile‐sodium methallylsulfonate copolymer is detected by X‐ray diffraction in dimethyl formamide and glycerol‐dimethyl formamide solutions in the range of polymer concentration (0.14, 0.325 mol/mol). Kinetics of isothermal ordering are followed by NMR for various temperatures, polymer concentration of the solutions and polymer tacticities. The rate of polymer ordering increases upon either a decrease of the temperature, an increase of the polymer concentration or an increase of the percentage of isotactic triads. Mandelkern's model of isothermal polymer crystallisation is applied to estimate the size of critical crystalline nuclei. Assuming that crystallites growth is negligible along polymer chain axis, one can deduce the maximal size of crystallites along this axis. The size of the crystallites perpendicularly to polymer chain axis is evaluated by X‐ray diffraction. It is found to be of the order of 100 Å.
Polymerisation of intercalated solvents in gels; An attempt to obtain molecular blending
Authors: Corstjens Tosca , Rastogi Sanjay , Lemstra Piet
Published: March 2011

Recent studies performed on gels like syndiotactic polystyrene/benzylmethacrylate and poly‐benzyl‐L‐glutamate/benzylmethacrylate indicate that the solvent molecules can be intercalated between or within the helices of the polymer. The present paper describes the UV polymerisation of these intercalated solvents. It was found that for both systems the solvent stays intercalated between the helices after polymerisation. This method can therefore be used to blend two immiscible polymers on a molecular scale.
Chemical separations by nanoporous crystalline samples of syndiotactic polystyrene
Authors: Guerra Gaetano , Milano Giuseppe , Venditto Vincenzo , Loffredo Fausta , De Ballesteros Odda Ruiz , Cavallo Luigi , De Rosa Claudio
Published: March 2011

Chemical separations based on absorption phenomena into syndiotactic polystyrene samples including a nanoporous crystalline phase are described. These separation phenomena are due to the presence into the crystalline phase of cavities whose size and shape have been studied through sorption experiments relative to linear hydrocarbons and through calculation procedures relative to the available crystalline structures of different polymorphic and clathrate forms of syndiotactic polystyrene.
Influence of water on the physical aging of poly(ethylene terephtalate)
Authors: D'Aniello Concetta , Romano Gennaro , Russo Roberto , Vittoria Vittoria
Published: March 2011

Physical aging in polyethylene terephtalate (PET) has been studied on samples well characterized in terms of aging history and their content of water. This allows us to better understand the role played by water in the complex phenomenology of the physical aging in a hygroscopic material as PET. No appreciable changes in the thermal behavior in the sample aged in water at room temperature for one month were noted, while substantial changes were observed in samples aged in more severe conditions like 50°C under vacuum and 50°C in water for one month. The results are consistent with the formation of small regions in which segments of chains are closely packed.
Behavior of polymers at surfaces and interfaces as observed in simulated systems
Authors: Pakula Tadeusz
Published: March 2011

Cooperative motion algorithm (CMA) is used to simulate polymer chains in three types of dense systems reflecting special cases of polymer behavior at surfaces and interfaces: polymer brushes with variable grafting density in the range 0–1, both in a neutral solvent and in a polymer melt, layers of end‐functionalized polymers between parallel end‐adsorbing walls, and copolymers of various distributions of comonomer units (random, block and gradient copolymers) at interfaces with noncompatible polymers.
Polysoaps and biopolymers: The effect of secondary structure on the extension elasticity
Authors: Borisov Oleg V. , Halperin Avraham
Published: March 2011

Extension of DNA and the protein titin reveals a plateau in the force vs. end‐to‐end distance diagram. A similar feature is predicted for the stretching elasticity of long polysoaps. These are linear hydrophilic chains that incorporate, at intervals, covalently bound amphiphilic monomers. In water, the amphiphilic monomers self‐assemble into intrachain micelles thus endowing the chain with a secondary structure. The similarity in the force laws is traceable to the equilibration of the secondary structure. For polysoaps forming a linear string of micelles, the plateau is associated with a coexistence of weakly perturbed micelles and fully dissociated amphiphiles. Similar scenarios can be invoked to explain the behaviour of DNA and titin. The resulting functional form seems to depend only weakly on the precise nature of the system.
Unusual adsorption behavior of polymers in layered structures
Authors: Sommer Jens‐Uwe , Blumen Alexander
Published: March 2011

We studied the conformations of polymer chains embedded in regular lamellar matrices such as microphase‐separated block copolymer melts or lipid/water systems. In such quasi‐one‐dimensional systems, the host plays the role of a nearly‐periodic external potential. A probe chain can get trapped with the localization length L at isolated defects, when its degree of polymerization N exceeds a cross‐over value NL. Interestingly, the radius of gyration, Rg, of the chain displays a minimum as a function of the defect density, ρ, the minimum being estimated by ρcL ≃ NL/N. Using Monte Carlo simulation, we underline the non‐monotonic behavior of Rg and calculate Green's function for various defect densities. On the same vein, the mean square displacement of the monomer units at large times shows a pronounced minimum as a function of the defect density, ρ.
Structure‐property correlations of non‐starch food polysaccharides
Authors: Bemiller James N.
Published: March 2011

Gums, the majority of which are polysaccharides, have a wide variety of chemical structures, a range of physicochemical properties, and impart a range of functionalities to foodstuffs and prepared foods.
Unique properties of high viscosity gums
Authors: Hoppe Craig A. , Goswami Animesh
Published: March 2011

Guar gum, a galactomannan from the seed endosperm of the legume, Cyamopsis tetragonolobus, is an important food stabilizer used in a variety of food products ranging from sauces to ice cream. Two guars having viscosities 13‐250% higher than conventional guars were studied. Viscosity, effect of shear rate on viscosity, synergy with xanthan gum, granulation, galactomannan content, molecular weight, and scanning electron microscopy of the guar types were evaluated. At equal usage levels of guar, the high viscosity type showed a higher viscosity alone and in combination with xanthan gum under all conditions tested. The high viscosity products have electron microscopic morphology that is more elongated and molecular weights which are greater than normal guars. These factors are discussed in light of the viscosity differences which exist between these products.
Physical properties of xanthan, galactomannan and their mixtures in aqueous solutions
Authors: Rinaudo M. , Milas M. , Bresolin T. , Ganter J.
Published: March 2011

Some new information on the conformation of xanthan in aqueous solutions is given. A single helical chain conformation characterizes xanthan in the native state. When heated over the critical temperature for conformational change ( helixŕ coil), the xanthan is denatured and renatured when it is cooled down in a localy double helical structure. A galactomannan was also characterized and its persistence length was obtained (Lp ≈︁ 90A°). Then mixtures of the galactomannan and xanthan were investigated to propose a mechanism for the specific gelation. From the results of microcalorimetry and circular dichroism, it is concluded that a complex is formed between one disordered xanthan chain and one galactomannan chain and that an ordered conformation is stabilized at temperatures lower than 25°C when the galactomannan has a M/G ratio of ≈︁ 3. This temperature corresponds to the sol‐gel transition. This is the first time that a structure of the crosslink points is demonstrated.
Rheology of carboxymethylcellulose made from bacterial cellulose
Authors: Cheng H. N. , Takai Mitsuo , Ekong Ekong A.
Published: March 2011

Partly as a result of the high solution viscosity of bacterial cellulose, carboxymethylcellulose (CMC) derived from this material exhibits shear‐thinning and thixotropic properties. With suitable sample treatment, the CMC solution shows gel‐like rheology suggesting the presence of a three‐dimensional network. This behavior is consistent with heterogeneous substitution of the carboxymethyl functionality on the polymer chains. For comparison, bacterial cellulose is also degraded by either acid or ultrasound to reduce its molecular weight and converted to CMC. The flow behavior of the resulting CMC solutions is nearly Newtonian with slight shear thinning but no thixotropy, suggesting that the carboxymethylation reaction is almost random.
The measurement of mass and size distributions, conformation, and branching of important food polymers by mals following sample fractionation
Authors: Chen Michelle Hong , Wyatt Philip J.
Published: March 2011

Three distinctive food polymers (ultra high molar mass amylopectin, guar gum, and hemi‐cellulose) were chosen as model samples to illustrate the use of multi angle light scattering (MALS) detection in conjunction with size exclusion chromatography (SEC) separations for the characterization of such macromolecules. By combining SEC and MALS, absolute molar mass, rms radius and their distributions can be measured readily without reference to any molar mass standards and without the need to make structural assumptions. In addition, the conformation and branching of those polymers can be derived also.
NMR of casein hydration and activity in solutions with ions
Authors: Mora‐Gutierrez Adela , Farrell Harold M. , Kumosinski Thomas F.
Published: March 2011

Oxygen‐17 NMR studies of caseins isolated from fresh milk of several species were carried out in concentrated electrolyte solutions as a function of both protein and electrolyte concentration. Molecular dynamics simulations of ion and water binding to caseins are compared with the experimental observations by 0–17 NMR of caseins in solutions with ions. Protein activities are also determined by utilizing Wyman's theory of linked functions with a detailed model of ion binding to casein.
Thermodynamic linkage of ion binding and hydration in myofibrillar protein solutions determined from multinuclear spin relaxation studies
Authors: Baianu Ion C. , Kumosinski Thomas F. , Mora‐Gutierrez Adela , Ozu Eiichi M. , Lioutas T. S. , Bechtel P. J.
Published: March 2011

The mechanisms for the anionic and cationic interactions with myofibrillar proteins in aqueous solutions were investigated by nuclear magnetic resonance over a wide range of salt concentration. Markedly nonlinear dependeces of the 17O and 23Na NMR transverse relaxation rates on salt concentration were analyzed with a thermodynamic linkage model of salt‐dependent solubility and hydration (ligand‐induced association model), according to Wyman's theory of linked functions. Nonlinear regression analysis of both 17O and 23Na NMR data suggested cooperative, reversible binding of hydrated ions to myofibrillar proteins. Both ions and water were found to exchange fast, on the NMR timescale, between the binding sites of the myofibrillar proteins and the aqueous solution. At sodium chloride concentrations higher than about 0.1 grams salt/gram water, ion activities have marked effects upon the NMR relaxation rates of both ions and water. A salt activity model allowed quantitative fitting of the NMR data at high salt concentrations. The effect of neglecting the ion activity in solutions of myofibrillar proteins was also estimated and compared with the ligand‐induced, cooperative association model for myofibrillar proteins. The comparison between the 17O and 23Na results strongly suggests that water is exchanged as the hydrated ion species between the myofibrillar protein binding sites and the bulk, aqueous solution.
Segmental orientation and chain relaxation of polymers by fourier transform infrared dichroism
Authors: Lachenal Gilbert , Ozaki Yukihiro
Published: March 2011

Fourier transform infrared dichroism has been used to investigate molecular orientation in polymeric materials. It is first applied to characterize network behavior in some elastomeric systems such as model networks of poly(dimethylsiloxane). The strain dependence of segmental orientation is analyzed through networks of known degree of cross‐linking and experimental results are compared with calculation predictions based on the rotational isomeric state formalism. Infrared dichroism spectroscopy has also been used to analyze orientational relaxation in binary blends of long and short polystyrene chains. The effect of short deuterated chains (Mw = 3000 to 72000) on the orientational relaxation of long entangled chains (Mw = 2 000 000) is examined in the bidisperse melts uniaxially deformed above the glass transition temperature. While the long chain relaxation is found to be dependent on the short‐chain concentration, the local orientational order of the latter is molecular weight dependent in agreement with the classical relaxation theories.
Structural changes in solvent‐induced crystallization of syndiotactic polystyrene viewed from the time‐resolved measurements of infrared/Raman spectra and X‐ray diffraction
Authors: Tashiro Kohji , Ueno Yoko , Yoshioka Akiko , Kaneko Fumitoshi , Kobayashi Masamichi
Published: March 2011

Solvent‐induced crystallization behaviour has been investigated for the glass sample of syndiotactic polystyrene. The time‐resolved measurements of the Fourier‐transform infrared and Raman spectra and the X‐ray diffraction profile revealed the molecular and crystal structural change during the ordering process of polymer chains. On the basis of the idea of critical sequence length, the structural change in the conformational ordering process could be deduced. The crystallization rate was found to be affected remarkably by the kind of solvent: chloroform gave higher crystallization rate than benzene and toluene. This tendency was in contrast to that observed for the gelation process from the dilute solution: the gelation rate was chloroform «benzene. This high contrast between the crystallization and gelation rates could be interpreted qualitatively in terms of the difference in the solubility of polymer in these solvents.
Gel‐state NMR investigation of crosslinked poly(methy1 methacrylate) incorporating 13C labeled ethylene glycol dimethacrylate
Authors: Mathias Lon J. , Steadman Scott , Anderson Kelly , Davis Rick , Jarrett William , Redfearn Richard D. , Bunn Alan
Published: March 2011

13C labeled ethylene glycol dimethacrylate (EGDMA) was used to form labeled crosslinked PMMA and model 13C labeled pendant double bond copolymers. Solution NMR was possible on solvent‐swollen samples containing less than 0.5% by weight EGDMA. Spectra confirm significant amounts of singly reacted EGDMA in fully polymerized networks. Peaks arising from the two most likely stereochemical triads (syndi‐ and heterotactic) were identified but no evidence of cyclic species was observed. Labeled EGDMA allowed observation of the crosslink site at concentrations as low as 0.02 wt‐% EGDMA.
Vibrational spectroscopic characterization of ethylene‐Co‐vinyl cinnamate copolymers before and after UV exposure
Authors: Coleman Michael M. , Hu Yin , Sobkowiak Maria , Painter Paul C.
Published: March 2011

Vibrational spectroscopic studies of a series of ethylene‐co‐vinyl cinnamate (EVCIN) copolymers, before and after exposure to UV radiation, are reported. The purpose of these studies is to determine whether or not significant reaction (photo‐crosslinking) of the cinnamate groups in EVCIN copolymers occurs upon UV exposure in the solid state as the concentration (fraction) of cinnamate groups is systematically reduced. By increasing the ethylene concentration in the EVCIN copolymers the cinnamate groups are “diluted” and progressively spaced apart in the copolymer. Somewhat surprisingly, we find that an EVCIN copolymer containing only 5 mole % vinyl cinnamate still undergoes a facile crosslinking in the solid state upon UV exposure.
The effect of branching on chain diffusion in ultralong N‐alkane crystals observed by 13C NMR
Authors: Driver Martin A. N. , Klein Philip G.
Published: March 2011

13C NMR progressive saturation measurements are used to investigate solid state chain diffusion in semicrystalline alkanes. Monodisperse, ultralong n‐alkanes, of 198 and 191 carbon atoms in length, are characterized and prepared in such a way that they comprise crystals containing chains which are exclusively of once‐folded conformation. This preparation is confirmed with DSC and SAXS. The progressive saturation experiments show that the longitudinal relaxation of magnetisation is consistent with a solid state chain diffusion process. Reptation and one‐dimensional diffusion models are demonstrated to satisfactorily represent the data. The addition of branches to the alkane chains is shown to result in a decrease in the diffusion coefficient. The obtained diffusion coefficients range from 0.0918 nm2s−1 for the linear chain to 0.016 nm2s−1 for a chain with a branch 4 carbons in length. These diffusion coefficients are consistent with those previously obtained for polyethylenes.
Effect of molecular orientation on the biodegradability of aliphatic polyester
Authors: Yoo Eui Sang , Im Seung Soon
Published: March 2011

The effect of morphological microstructure on the biodegradability of aliphatic polyester, poly(ϵ ‐caprolactone) (PCL) was studied in terms of crystallite size, crystallinity and amorphous and crystalline orientation factors. Microstructural changes during hydrolysis/biodegradation of the drawn PCL films were investigated by the conventional small and wide angle X‐ray scattering methods. The lower was the draw ratio, the higher the hydrolytic degradability or biodegradability. With the increase of the hydrolysis time, the long period, at earlier stage, decreased; then slightly recovered and the crystallinity increased while the lamellar thickness remained unchanged. The amorphous orientation factors start to decrease at earlier stage and gradually go down to zero before the end of hydrolysis. In the case of crystalline orientation factor, although the values decrease with increasing hydrolysis time, they do not reach zero point. After the biodegradation for 60 days, crystallinity, crystal lateral size and lamellar thickness in all drawn PCL films decreased, and then it was confirmed that even crystalline regions were degraded for long term biodegradation test.
Synthesis and second harmonic generation studies of nlo‐functionalized polyimides
Authors: Shim Hong‐Ku , Yoon Chong‐Bok , Woo Han Young
Published: March 2011

Several NLO‐functionalized polyimides were synthesized through novel synthetic pathways and their NLO properties were characterized. For preventing the disadvantage in poly(amic acid) precursor route, the Mitsunobu reaction and alternative synthetic route for NLO polyimides were chosen. The second‐order NLO coefficients (χ(2)) of the synthesized polyimides were between 48pm/V and 122pm/V. The thermal stability of nonlinearity characterized showed that all polyimide films retain their NLO activities at temperatures below 100°C.
Photoacid‐generating sulfonyloxymaleimide polymers and their application to photoimaging
Authors: Ahn Kwang‐Duk , Chung Chan‐Moon
Published: March 2011

Synthesis and properties of photoacid generating polymers based on four sulfonyloxymaleimides (RsOMI), N‐(tosyloxy)maleimide (TsOMI), N‐(methanesulfonyloxy)maleimide (MsOMI), N‐(trifluoromethanesulfonyloxy)maleimide (TfOMI), and N‐(10‐camphorsulfonyloxy)maleimide (CsOMI) are described. The RsOMI polymers photochemically produce corresponding sulfonic acids (RsOH), TsOH, MsOH, TfOH and 10‐camphorsulfonic acid (CSA) which can catalyze deprotection of the acid‐labile t‐BOC groups in the same polymer chains via a chemical amplification process. The photoacid generating polymers with concurrent acid‐labile groups offer great potential for applications in functional transformation and photoimaging.
Complexation behaviour of polymers with pendant cyclodextrin side groups
Authors: Adams Jörg , Hollas Markus , Chung Myung‐Ae , Park Joon Woo , Hong Ji Hyun , Park Kwanghee Koh
Published: March 2011

The influence of the chain conformation on the formation of polymeric supramolecular complexes as well as the influence of the complexation on the conformation of the polymer chain has been studied. The complexation of pyrene into the cavity of β‐cyclodextrin (β‐CD) was investigated in aqueous solutions of β‐CD substituted poly(allylamine) (PAA) under variation of external parameters, i.e. temperature, pH, ionic strength and addition of urea. The observed changes of the complexation constant K for the formation of the 2:1 β‐CD/pyrene complex can be explained by a change of the chain flexibility which leads to a variation of the mean distance between neighbouring β‐CD‐moieties along the polymer chain. The intra‐chain association of the decyl group with β‐CD in PAA with co‐pendant decyl and β‐CD is disrupted by the addition of 1‐adamantanamine HCl resulting in a more extended structure of the polymer. The β‐CD moiety in PAA‐CD shows one order of magnitude greater affinity to 2‐(p‐toluidyl)naphthalene‐6‐sulfonate than the native β‐CD and the affinity increases further by the presence of decyl side groups.
Highly efficient template‐based preparation of shape‐persistent macrocyclics
Authors: Höger S.
Published: March 2011

The synthesis of shape‐persistent macrocycles via oxidative dimerization or trimerization of rigid bisacetylenes (via Glaser coupling) is described. To enhance the yield of the desired target structures, the precursors are temporarily covalently bound to a template resulting in an intramolecular coupling instead of an intermolecular coupling. As a result, product yields up to over 90 % are observed.
Temperature dependence of radiation effects on polymers
Authors: Tabata Yoneho , Oshima Akihiro
Published: March 2011

Temperature dependence of radiation effect on various polymers including hydrocarbon and fluorocarbon polymers was investigated. Gas evolution and mechanical properties were measured in a wide range of temperatures. G‐values of chain scission and crosslinking were estimated. It has been made clear from those experimental results that radiation effect be profoundly affected by temperature. Particularly, significant changes of radiation effect in the melting region were found out.
Inorganic‐organic polymers as a route to biodegradable materials
Authors: Allcock Hairy R.
Published: March 2011

The polyphosphazene platform allows the design and synthesis of a broad range of different polymers, some of which have special properties as biodegradable materials. Different polyphosphazenes are produced mainly by means of macromolecular substitution reactions carried out on a reactive polymeric intermediate, poly(dichlorophosphazene), (NPCl2)n. Organic side groups such as amino acid esters, glucosyl, glyceryl, glycolate, lactate, or imidazolyl sensitize the polymers to hydrolysis to benign materials such as phosphate, ammonia, and the free side unit. Other polymers are of interest as the basis for hydrogels and microencapsulation materials.
Degradable plastic films for agricultural applications in Taiwan
Authors: Yang Shaw‐Rong , Wu Chin‐Hsiang
Published: March 2011

Tainan District Agricultural Improvement Station began in February 1991 to evaluate the feasibility of using degradable plastic films for horticultural crops production. Products from China, Korea, Israel, Germany, U.S.A. and Taiwan were used for comparison. Results are summarized as follows: Macro‐and micro‐environmental changes in different seasons affected the degradation time of the tested degradable plastic films. The silver/black bio/photo‐degradable PE films containing 20% starch from USI Far East Corporation degraded after 56, 83, 38, and 33 days when they were mulched in fall(October, 1991), winter(December, 1991), spring(April, 1992) and summer (August, 1992), respectively. The more starch incorporated, the faster the films degraded. No difference was observed in size, weight, yield, total soluble solids and heavy metal contents of the fruits of cantaloupe and watermelon grown on the beds mulched with various kinds of degradable PE films or traditional PE film. No difference was observed in yield as well as the heavy metal (Fe, Pb, Ni, Cu, Cd and Cr) contents in the edible part of the crops of cabbage mustard and head lettuce that were grown in the soil without or incorporated with debris of degradable PE films in 6 consecutive years. The same results were also obtained in another trial on cantaloupe and paddy rice for 4 consecutive years. Various amounts(0, 4, 8, 16, 32 and 64g) of used degradable PE films were seperately mixed with field soil. The mixed soil were used to grow paddy rice in clay pots. No difference was observed in plant height, length and weight of the spike, 1,000‐seed weight and the kernel per spike among the treatments at harvesting. Six pieces (each 10cm□10cm) of Bioplastics, Bioflex and Green choice biodegradable films were buried in a 8‐inch clay pot. Then head lettuce were planted in the pots. No difference was observed in head weight and qualities(vitamin C. total soluble solids and crude fiber)either among the treatments or the control. The weight losses for Bioflex, Bioplastics and Green choice were 58.4%,47.9% and 11.3%, respectively after 40 days.
Accelerated chemical degradation of polyacrylamide
Authors: Gao Jianping , Lin Tong , Wang Wei , Yu Jiugao , Yuan Shaojun , Wang Shaomin
Published: March 2011

The chemical degradation of polyacrylamide(PAM) at low temperature in aqueous medium was initiated by peroxides. The degradation degree of the polymer rose with the reaction time. The degradation degree of PAM depended not only on peroxide characteristic but also on the concentration of polyacrylamide and potassium persulfate, degradation temperature and original molecular weight of PAM. The results showed that the order of degradation degree of PAM in three peroxides is K2S2O8 > K2S2O8 — Na2S2O3 > H2O2. The degradation degree of PAM grew as reaction temperature, molecular weight of PAM, concentration of potassium persulfate and PAM increased.
Methodology in studying improvement of polyacrylates biodegradability
Authors: Gancet Christian , Pirri Rosangela , Dalens Jean Marc , Boutevin Bernard , Guyot Bernard , Loubat Cédric , Le Petit Jean , Farnet Anne Marie , Tagger Simone
Published: March 2011

The biodegradability of polyacrylic acid derivatives may be improved through introduction of some fragility points within the main carbon chains. These weakness points can be either hydrolizable bonds or oxidizable sites. Enzymatic hydrolysis and oxydative biomimetic degradation tests have been set up in order to quickly evaluate new polymeric structures, before their possible evaluation through microbial degradation by Candida tropicalis.
Novel lipase‐catalyzed ring‐opening copolymerization of oxiranes and dicarboxylic anhydride forming polyesters bearing carboxyl groups and their physicochemical properties and biodegradability
Authors: Matsumura Shuichi , Okamoto Takeshi , Tsukada Keisuke , Mizutani Noriyuki , Toshima Kazunobu
Published: March 2011

Oxiranes, such as benzyl glycidate and glycidyl phenyl ether, were copolymerized with dicarboxylic anhydride by lipase at a temperature between 60 and 80 °C to yield the corresponding polyesters bearing carboxyl or phenyl groups. Bulk polymerization, especially at 80 °C, and preferably using porcine pancreatic lipase, gave biodegradable polyesters with a molecular weight of greater than 10000. Poly(sodium carboxylate)s containing ester linkages in the backbone prepared in this study were readily biodegradable by the activated sludge and exhibited a calcium ion sequestration capacity.
Characterization of nanoparticles
Authors: Lechner M. D. , Mächtle W.
Published: March 2011

Nanoparticles with diameters from 1–100 nm are used in large quantities for very different applications. A precise determination of the important physical quantities (which are responsible for the application properties) such as diameter, particle size distribution, and surface is therefore very essential. The most common methods for the determination of these quantities are analytical ultracentrifugation (AUC) and dynamic light scattering (DLS). The paper demonstrates the techniques of getting a precise characterization of nanoparticles and suggests a new method for the correction of the sedimentation coefficient and its distribution with respect to the diffusion coefficient.
Phenomena of counterion binding, polyion complexation and polyion condensation
Authors: Nordmeier Eckhard
Published: March 2011

The article handles some aspects of polyelectrolyte research investigated during the last ten years at the university of Osnabrück. They are: counterion binding, polyion complexation, and polyion condensation. Fundamental features are presented that are common to the behaviour of most polyions. Another intention is to bridge a gap between synthetic and biological polyelectrolyte research. For this purpose, DNA condensation is reviewed in some detail.
Temperature and pH sensitive polymers in water ‐ from solution to thin films
Authors: Kuckling Dirk , Adler Hans‐Juergen P. , Arndt Karl‐Friedrich , Ling Long , Habicher Wolf Dieter
Published: March 2011

A series of temperature and pH sensitive polymers which contain both temperature and pH sensitive components were synthesised by copolymerization of N‐isopropylacrylamide (NIPAAm) and acrylamide derivatives containing a spacer and a sensitive headgroup. The cloud point and heat of transition (ΔHPT) of aqueous solutions of polymers with various compositions were measured by means of DSC. The observed cloud points and ΔHPT values strongly depend on the polymer composition and the pH value. The irradiation of dimethylmaleinimide groups (DMIAAm) bearing copolymers with UV light resulted in crosslinking of the polymers. The prepared thin layers showed fast temperature dependent swelling with transition temperatures similar to the uncrosslinked polymers.
Theory of relaxation spectra of polymer networks with interchain friction and long‐range hydrodynamic interactions
Authors: Gotlib Yuli YA.
Published: March 2011

The dynamic network model taken into account the friction relative to incompressible effective viscous medium (EVM), the hydrodynamic interactions of a network with the EVM, and the interchain friction is considered. Two collective network relaxation spectra (RS) arise. The first RS corresponds to the network motion relative to immobile EVM, the EVM does not take part in this motion. The second RS includes the combined viscous motion of the network and EVM because of long‐range hydrodynamic interactions. This RS is finite and narrow for infinitely large network. The symmetry of this motion is in concordance with that of incompressible EVM. The existence of interchain friction leads to the narrowing of both types of relaxation spectra.