bluuebunny/crossref_metadata_2025 huggingface dataset:
Scattering properties of multicomponent polymer solutions: polyelectrolytes, homopolymer mixtures and diblock copolymer
Authors: Borsali Redouane
Published: April 2003

This article reviews the understanding of static and dynamic scattering properties of multicomponent polymer systems in solution achieved during the past decade. We shall describe particularly ternary polymer systems which include polyelectrolyte solutions (polyion/counter‐ions/water), mixture of homopolymers (A and B)/solvent and the case of diblock copolymer (A‐B, linear or cyclic) solutions. The purpose of this paper is not an extensive survey of theoretical and experimental results obtained on the scattering behavior of these systems but rather an updating of recent results. For polyelectrolyte systems we shall focus, by means of scattering techniques, on the conformation of the polyelectrolyte chain and on the structure of the system induced by the dominant electrostatic interactions in solution involving polyions, counter‐ions and solvent. As for the mixture of homopolymers in solution and diblock copolymer/solvent systems, we shall mainly discuss their dynamic behavior and show that using linear response theory and the Random Phase Approximation (RPA), two relaxation modes describe the autocorrelation functions as revealed using dynamic light scattering (DLS) or/and Neutron Spin Echo (NSE) techniques: the first mode characterizes the concentration fluctuations and the second one the composition fluctuations. We shall discuss the scattering properties of these systems on the basis of recent developments with emphasis on possible coiling of the polyelectrolyte chain at low charge density and also how important parameters such as the mobility of the chain (diffusion process) and the interaction parameter (compatibility), which control the dynamics and the thermodynamics in homopolymer mixtures and diblock copolymer systems, could be deduced from scattering experiments.
On the stereoisomerization in thermal degradation of isotactic poly(propylene)
Authors: Sawaguchi Takashi , Seno Manabu
Published: April 2003

The terminal microstructure of the hydrogenated α,ω‐diisopropenyloligo(propylene) prepared by thermal degradation of isotactic poly(propylene) at 370°C was determined by means of 13C NMR spectroscopy, and therefrom the stereoisomerization reaction of the reacting polymer segment is discussed in relation to polymer dynamics. With respect to the asterisked carbons of the propyl end group CH3CH2*CH2(n‐Pr) and of the isopropyl end group (*CH3)2CH (i‐Pr) formed by hydrogenation, the mole fractions of triads (m meso, r racemo) Fmm = 0.64, Fmr = 0.09, Frr = 0.12 of n‐Pr‐*CH2 differ from the microtacticity of the main chain of telechelic oligomers, and the mole fraction of i‐Pr‐*CH3 is as follows: F(δtζt) + F(δeζe) = 0.74 (m); F(δtζe) + F(δeζt) = 0.26 (r). These results clearly show that the stereoisomerization occurs only at the asymmetric carbon near the end group of the telechelic oligomer. The value of the mole fraction of i‐Pr‐*CH3 is consistent with Fm = 0.73 (Fmm + Fmr) and Fr = 0.27 (Frr + Frm) of n‐Pr‐*CH2 at the outer position of the main chain rather than with Fm = 0.79 (Fmm + Frm) and Fr = 0.21 (Frr + Fmr) at the inner position. These results could be consistently traced by a simulation based on a reaction model including stepwise intramolecular hydrogen abstraction of the tertiary on‐chain macroradical near the center of the main chain before the successive β‐scission. This stepwise back‐biting is estimated to occur once (20%) and twice (80%) via a quasi six‐membered cyclic structure in a transition state, and occurs in a very limited part of the molecular chain.
Novel perylene‐containing polymers
Authors: Quante Heribert , Schlichting Peter , Rohr Ulrike , Geerts Yves , Müllen Klaus
Published: April 2003

Novel perylene‐containing polymers have been synthesized. They exhibit good solubilities in organic solvents and have good film forming properties. A water‐soluble perylene‐containing polyimide was obtained via sulfonation of the corresponding polyimide. Solubilities and spectral characteristics of these polymers are discussed as a function of their structures.
Polysiloxanes with benzophenone side groups: factors affecting their efficiency as free radical polymerization photoinitiators
Authors: Pouliquen Lydie , Coqueret Xavier
Published: April 2003

Functionalized silicone copolymers containing 2‐benzoylbenzoic acid (2‐BBA) ester side groups were evaluated as radical polymerization photoinitiators in the presence of an amine co‐reactant. Following up previous reports, the study of their efficiency conducted at various concentrations of the photoinitiating system in a model acrylate formulation was compared to that of the low molecular weight 2‐BBA ester. The photosensitive polysiloxanes were confirmed to exhibit a clear polymer effect, the type II photoinitiating efficiency being enhanced when the chromophores are present as pendant groups on polymer chains and when the tertiary amine (ethyl 4‐dimethylaminobenzoate) is free in the medium and with r = [amine]0/[2‐BBA]0 = 1. The influence of the increase of r in the range 0.5‐2 on the initial polymerization rate at constant concentration of BBA was shown to improve the initial rate of polymerization as well as the limiting conversion. N,N‐Dimethyl and N,N‐diethyl aliphatic or aromatic low molecular weight aminoesters were studied as co‐initiators to gain a deeper insight into the process. The effect of the incident UV beam wavelength was also examined and showed the complex influence of the amine structure on reactivity. Light absorption characteristics, reducing power and aptitude to charge transfer initiation of acrylate polymerization seem to contribute to various extents to overall efficiency.
The crystal structure and drawing‐induced polymorphism in poly(aryl ether ketone)s, 1. Poly(oxybiphenyl‐4‐4′‐diyloxy‐1,4‐phenylenecarbonyl‐1,3‐phenylenecarbonyl‐1,4‐phenylene)
Authors: Wang Shanger , Wang Junzuo , Mo Zhishen , Zhang Hongfang , Wu Zhongwen
Published: April 2003

Crystal structure and polymorphism induced by uniaxial drawing of a poly(aryl ether ketone) [PEDEKmK] prepared from 1,3‐bis(4‐fluorobenzoyl)benzene and biphenyl‐4,4′‐diol have been investigated by means of transmission electron microscopy (TEM), electron diffraction (ED), wide‐angle X‐ray diffraction (WAXD), and differential scanning calorimetry (DSC) techniques. The melting and recrystallization process in the temperature range of 250‐260°C, far below the next melting temperature (306°C), was identified and found to be responsible for the remarkable changes in lamellar morphology. Based on WAXD and ED patterns, it was found that crystal structure of isotropic‐crystalline PEDEKmK obtained under different crystallization conditions (melt‐crystallization, cold‐crystallization, solvent‐induced crystallization, melting‐recrystallization, and crystallization from solution) keeps the same mode of packing, i.e., a two‐chain orthorhombic unit cell with the dimensions a = 0.784 nm, b = 0.600 nm, and c = 4.745 nm (form I). A second crystal modification (form II) can be induced by uniaxial drawing above the glass transition temperature, and always coexists with form I. This form also possesses an orthorhombic unit cell but with different dimensions, i.e., a = 0.470 nm, b = 1.054 nm, c = 5.064 nm. The 0.32 nm longer c ‐axis of form II as compared with form I is attributed to an overextended chain conformation due to the expansion of ether and ketone bridge bond angles during uniaxial drawing. The temperature dependence of WAXD patterns for the drawn PEDEKmK suggests that form II can be transformed into the more stable form I by relaxation of overextended chains and relief of internal stress at elevated temperature in absence of external tension.
High‐pressure free‐radical copolymerization of ethene and 2‐ethylhexyl acrylate
Authors: Buback Michael , Dröge Thomas , Herk Alex Van , Mähling Frank‐Olaf
Published: April 2003

The free‐radical copolymerization of ethene (E) and 2‐ethylhexyl acrylate (EHA) is studied between 150 and 250°C and at pressures from 1500 to 2500 bar. The reactions which were induced either thermally or laser‐photochemically are carried out in two types of continuously operated devices and also within a batch reactor. The precision in the determination of reactivity ratios is considered in detail for the continuous experiments taking the error structure of the copolymer composition measurement into account. The reactivity ratios rE and rEHA at 220°C and 2000 bar are found to be 0,050 ± 0,002 and 3,9 ± 0,9, respectively. From the ethene rich reaction mixtures rE is available with higher precision than is rEHA. The E/EHA reactivity ratios are found to be very close to literature data for the E/butyl acrylate (BA) copolymerization. Fitting of the combined data set, for E/EHA and E/BA, yields for the activation energy and activation volume of the ethene reactivity ratio EA(rE) = (11,9) kJ · mol−1 and ΔV≠(rE) = ‐(8,2 ± 3,5) cm3 · mol−1, respectively.
High and low molar mass 3‐alkyl‐1,4‐pentazadienes. Synthesis and photolysis
Authors: Baindl Andreas , Lang Armin , Nuyken Oskar
Published: April 2003

High and low molar mass compounds containing the 3‐alkyl‐1,4‐diarylpentazadiene group were synthesized in the reaction of aromatic diazonium salts with primary amines. These high nitrogen compounds are characterised by high photosensitivity and thermostability. The photolytic decomposition was studied in detail with respect to the substitution at the aromatic moieties and at N3 of the pentazadiene chromophore. Electron donating aromatic substituents were found to increase photosensitivity and decrease thermostability whereas electron withdrawing aromatic substituents cause higher photolytic and thermolytic stability. A little influence of the alkyl group at N3 on the photosensitivity of the pentazadiene group was observed. Photolysis was investigated by means of UV/Vis spectroscopy and obeys first order kinetics for some compounds under investigation. Gel permeation chromatography (GPC) measurements during photolysis of pentazadiene polymers prove that irradiation with UV light causes irreversible chain degradation. Thermolysis in bulk was studied for all compounds by differential scanning calorimetry (DSC). In contrast to the results of the photolysis the alkyl substituent at N3 has an effect on the thermostability of the pentazadiene chromophore.
Liquid‐crystalline polyimides, 28. Thermoplastic elastomers with smectic hard phase based on 3,5:3′,5′‐biphenyltetracarboximides
Authors: Kricheldorf Hans R. , Linzer Volker
Published: April 2003

Two series of copoly(ether‐imide)s were prepared by polycondensation of 3,5:3′,5′‐biphenyltetracarboxylic anhydride (BTCA) and mixtures of 4,4′‐(nonamethylenedioxy)dianiline and polytetrahydrofuran (polyTHF) containing two amino end groups. Two samples of polyTHF were used, one sample with a number‐average molecular weight Mn = 750 and another sample with Mn around 2100. All polycondensations were conducted in the form of a “one‐pot procedure” in refluxing m‐cresol. The mole ratio of poly‐THF and 4,4′‐(nonamethylenedioxy)dianiline was varied, so that the length of the hard segments varied.

Wide‐angle X‐ray scattering (WAXS) powder patterns proved that at least the hard phase of those poly(ether‐imide)s with relatively long hard segments possesses a smectic‐crystalline layered structure analogous to that of the homopolymer derived from BTCA and 4,4′‐(nonamethylenedioxy)dianiline. Only one polyimide showed highly elastic behavior.
Calorimetric study of tetrahydro‐1,3‐oxazin‐2‐one and poly(oxy‐1,3‐propanediyliminocarbonyl), and the polymerization/depolymerization equilibrium
Authors: Lebedev Boris V. , Smirnova Natal'ya N. , Kiparisova Elena G.
Published: April 2003

In adiabatic vacuum and dynamic calorimeters the temperature dependence of the heat capacity Cp0 of tetrahydro‐1,3‐oxazin‐2‐one (THO) and poly(oxy‐1,3‐propanediyliminocarbonyl) (PTHO) was studied between 5 and 500 K. The melting temperature of the monomer and the polymer, the enthalpies of melting of THO and the glass transition temperature of PTHO were determined. In a calorimeter with a static bomb and an isothermal shield the energies of combustion ΔUcomb of the monomer and the polymer were measured. From the experimental data the thermodynamic functions Cp0, H0(T) – H0(O), S0(T), G0(T) – H0(0) were calculated in the range of 0 to 450 K, and enthalpies of combustion ΔHcomb0 and thermochemical parameters of formation ΔHf0, ΔSf0, ΔGf0 of the compounds studied were estimated at T = 298.15 K and standard pressure. The results obtained were used to estimated the thermodynamic characteristics of the equilibrium of THO polymerization in bulk (ΔHpol0, ΔSpol0, ΔGpol0), with opening of the six‐membered ring and formation of the linear polymer PTHO, in the range 0 to 450 K. It was found that the ΔGpol0 values are always negative and change from −18 kJ · mol−1 at 0 K to −14 kJ · mol−1 at 450 K. Thus, the process equilibrium is everywhere shifted towards the formation of the polymer. The upper (ceiling) limiting temperature of THO polymerization in bulk at standard pressure is Tceil = 750 K, that is, considerably higher than the temperature of the onset of the thermal polymer decomposition (450 K).
Infrared temperature studies of a simple polyurea
Authors: Coleman Michael M. , Sobkowiak Maria , Pehlert George J. , Painter Paul C. , Iqbal Tahir
Published: April 2003

Infrared temperature studies of a polyurea formed from 2‐methylpentane‐1,5‐diamine and 4,4′‐methylenebis(phenyl isocyanate) are presented, together with those of two model diureas, 2‐methylpentane‐1,5‐diphenylurea and ethylene diphenylurea. The main thrust of the work concerns the interpretation of the infrared changes that are observed in ordered and disordered hydrogen bonded ureas.
Polymers by “criss‐cross”‐cycloaddition, 7. Segmented block copolymers
Authors: Maier Gerhard , Fenchl Andrea , Sigl Gerhard
Published: April 2003

“Criss‐cross”‐cycloaddition of 4,4′‐diisocyanatodiphenyl ether and 4‐methoxybenzaldazine was used to synthesize α,ω‐diisocyanato telechelics of molecular weights between 1 600 and 3 900. These precursors were reacted with different α,ω‐dihydroxy functionalized aliphatic polyethers to produce segmented block copolymers in which the precursors obtained by cycloaddition reaction provide hard segment domains embedded in a polyether soft segment matrix. The resulting materials were soluble in common organic solvents such as tetrahydrofuran and chloroform and were characterized by spectroscopic techniques (1H‐, 13C NMR, IR spectroscopy) as well as gel permeation chromatography (GPC) for molar mass determination. The block copolymers were molded in a hot stage press, and the resulting samples were characterized by differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA) and stress‐strain measurement. The materials with a hard segment fraction below 0.36 and a molecular weight above M̄n = 90 000 were elastomers with ultimate elongations above 700%.
Thermal and mesogenic properties of semirigid polyamides based on mono‐ or trimethylsubstituted 1,3‐diaminobenzenes
Authors: Sato M. , Ujiie S.
Published: April 2003

Thermal and mesogenic properties of semirigid polyamides composed of one benzene ring with a kinked linkage and various aliphatic chains in the repeating unit, which are derived from three 1,3‐diaminobenzenes and aliphatic dicarboxylic acids, were examined. Only two polyamides with a long aliphatic chain (C18H36), based on 4‐methyl‐ and 2,4,6‐trimethyl‐1,3‐diaminobenzenes, form mesophases although the polymers exert nontraditional mesogenic units. Formation of the mesophase in the latter case depends on the inherent viscosity, i.e., polymers with lower inherent viscosity (⩽1,47 dL/g) form a layered structure by intermolecular interaction via hydrogen bonding of the amide linkage.
Interpolyelectrolyte complexes of poly[4‐(but‐3‐en‐1‐ynyl)‐1‐methylpiperidin‐4‐ol] with poly(carboxylic acids)
Authors: Kudaibergenov Sarkyt E. , Nurkeeva Zauresh S. , Sigitov Vladimir B. , Zh. Akimbekova K. , Ushanov Valerii Zh.
Published: April 2003

The formation of polyelectrolyte complexes (PEC) between linear or crosslinked poly[4‐(but‐3‐en‐1‐ynyl)‐1‐methylpiperidin‐4‐ol] and linear as well as crosslinked poly(acrylic acid) and poly(methacrylic acid) was studied by potentiometric, conductimetric, turbidimetric, viscometric and volumetric methods in aqueous solution. The composition of PEC particles depends on the conformational state of the interacting macromolecules. The destruction of PEC particles into the individual components takes place at an ionic strength μ > 1 × 10−2 mol/L. The addition of organic solvents causes the conformational transition of PEC particles from the compact structure to an extended one. The sorption of linear polyelectrolytes by networks is accompanied by the shrinking of the polyelectrolyte gels. The kinetics of sorption increases with increasing temperature, ionic strength of the solution and ionization degree. The destruction of PEC consisting of oppositely charged linear and crosslinked polyelectrolytes takes place at high ionic strength of the external solution. The completeness of interpolyelectrolyte reactions with participating of linear and crosslinked poly[4‐(but‐3‐en‐1‐ynyl)‐1‐methylpiperidin‐4‐ol] was detected by the disappearance of the Bohlman band at 2 800 cm−1. The kinetics of sorption of linear polyelectrolytes by crosslinked polyelectrolytes as well as of the competition reaction which is accompanied by the destruction of PEC composed of oppositely charged linear and crosslinked polyelectrolytes was also studied.
Synthesis and characterization of monomethacrylate‐functionalized self‐organizing crown ether compounds
Authors: Percec Virgil , Zipp Gabriela , Johansson Gary , Beginn Uwe , Möller Martin
Published: April 2003

Synthesis and characterization of methacrylate‐monofunctionalized crown ether compounds based on derivatives of 2‐hydroxymethyl‐1,4,7,10,13‐pentaoxacyclopentadecane and 4′‐hydroxymethyl‐1,4,7,10,13‐pentaoxabenzocyclopentadecane is described. By differential scanning calorimetry (DSC) and thermooptical analysis (TOA) it is shown that the synthesized compounds and their sodium triflate complexes exhibit columnar mesophases.
Hydrolysis and release behavior of hydrolyzable poly(etherurethane) gels derived from saccharide‐, L‐lysine‐derivatives, and poly(propylene glycol)
Authors: Wibullucksanakul Sirinat , Hashimoto Kazuhiko , Okada Masahiko
Published: April 2003

Four different poly(ether urethane) gels were prepared by polyaddition of saccharide derivatives (1, 2, 3α, or 3β) and poly(propylene glycol) with an L‐lysine‐derived diisocyanate, methyl (S)‐2,6‐diisocyanatohexanoate (4). Dibutyltin dilaurate and triisocyanate 5, that was also derived from L‐lysine, were used as a catalyst and a crosslinking agent, respectively. Hydrogels containing 1, 2 or 3α were hydrolyzed in phosphate buffers (pH 5.5, 7.0, 8.0) at 27°C, while the hydrolysis of the gel bearing 3β did not occur even after immersion for 3 months. Release of 5(6)‐carboxyfluorescein (CF) and magnesium 8‐anilino‐1‐naphthalenesulfonate (ANS) from the hydrogels was investigated in buffers of different pH. The release behavior was significantly controlled by the degree of hydrolysis of the gels. Both hydrolysis and the release behavior of these gels depended on the pH value.
The width of miscibility gaps, measured by scattering
Authors: Hellmann E. H. , Hellmann G. P.
Published: April 2003

Incompatible polymers yield two‐phase binary blends at almost all compositions. In equilibrium, the blends consist of two coexisting phases which have frequently very one sided compositions: Much of one component contains little of the other. The small content of the minor component, the so‐called “partial miscibility”, is important for some properties. But it is difficult to measure. Conventional techniques to determine miscibility gaps which rely on transparency and turbidity fail when the gaps are too wide. More reliably, the composition of the coexisting phases can be extracted from X‐ray or neutron scattering data. A series of blends of poly(methyl methacrylate) (PMMA) and random copolymers SxMMAl−x of styrene and MMA, of which the degree of incompatibility was varied via the copolymer composition x, was studied by small angle neutron scattering. The interactions of the polymer components were measured in homogeneous and demixed blends. The demixed blends yield at high wave vectors a scattering equal to the scattering of the two coexisting phases, superposed. The composition of the coexisting phases was extracted from the slope of the Zimm curve which responds very sensitively even when the compositions are extreme. Miscibility gaps as wide as 99.7% could be determined.
Synthesis and characterization of functional polymer films containing trimethylsilyl groups
Authors: Shim Hong‐Ku , Jang Min‐Sik , Hwang Do‐Hoon
Published: April 2003

Poly(2‐methoxy‐5‐trimethylsilyl‐1,4‐phenylenevinylene) (PMTSPV) was prepared as thin film via the water‐soluble precursor route, and its electrical and optical properties were studied. The conductivity values of drawn (L/L0 = 7) and undrawn FeCl3‐doped PMTSPV films were 0.1 and 0.5 · cm−1, respectively. The electroluminescence device was fabricated with PMTSPV as an emitting layer, and ITO and aluminium as hole‐injection and electron‐injecting electrodes, respectively. The threshold voltage of the device was about 4 V, and the emission maximum was at about 560 nm, with quantum efficiency of 2 × 10−4% (emitted photons per electron), which corresponds to yellow light emission. The χ(3) for the PMTSPV film was investigated by using the third‐harmonic generation method at 1907 nm fundamental wavelength, and found to be 1.0 × 10−11 esu.
Synthesis and mesomorphic properties of side chain liquid crystalline polymers having thiadiazole ring
Authors: Lee Jaehwan , Hong Sung Il , Hwang Seung Sang
Published: April 2003

New liquid crystalline monomers having 1,3,4‐thiadiazole ring as mesogen were synthesized by using Lawesson's reagents to prepare the thiadiazole ring and acryloyl chloride and methacryloyl chloride to introduce the vinyl group. These monomers were polymerized in the presence of 2,2′‐azoisobutyronitrile as initiator in THF. All monomers and polymers show cholesteric behavior and a broad chiral smectic C* phase. As the spacer length increases, the phase transition temperature is lowered and the polymers show higher phase transition temperatures and improved mesophase stabilities compared to the corresponding monomers.
Molecular microstructure dependence of space charges in polymers. Coupling of thermal step (TS) and thermally stimulated discharge current (TSDC) methods in PVC after nucleophilic substitution
Authors: Guarrotxena Nekane , Vella Nathalie , Toureille Alain , Millán José‐Luis
Published: April 2003

The space charge distribution, a basic electrical property of insulating materials, has been studied for a poly(vinyl chloride) (PVC) sample before and after nucleophilic substitution reaction up to various degrees with sodium benzenethiolate (NaBT) in cyclohexanone (CH) solution, so as to modify in a controlled way the content of the isotactic tetrad mmr and the heterotactic pentad rrmr located at the end of isotactic and syndiotactic sequences, respectively. We investigated the influence of mmr and rrmr structures on the number and type of electrical charges accumulated in the material when submitting it to an electrical field. To differentiate between the polarization charges and the trapped charges, coupling of the “thermal step” (TS) and the “thermally stimulated discharge current” (TSDC) techniques was applied. Both types of charges were proved to be related chiefly to the conformations GTTG‐TT and GTGTT, having higher free volume and local mobility, characteristic of mmr structure.
Rheological characteristics of semi‐dilute chitosan solutions
Authors: Mucha Maria
Published: April 2003

The present work is concerned with experimental results on rheological characteristic properties of semi‐dilute chitosan solutions in weakly acetic acid. The flow measurements were conducted on solutions of chitosan of various deacetylation degrees DD (62.8%–86.7%) with changing experimental conditions such as concentration (up to 5 g/100 mL), temperature (20°C–41°C) and shear rate applied (up to 103s−1). Chitosan solutions behave generally as a typical non‐Newtonian shear‐thinning fluid with a characteristic n‐parameter lower than 1. The rheological n‐parameter decreases with decreasing deacetylation degree and increasing solution concentration but it increases with increasing temperature. Because of strong intermolecular hydrogen bonding even at low concentration the chitosan macromolecules have a tendency to entangle and to network formation. The density of the molecular entanglements in the chitosan solution depends on concentration, temperature and shear rate applied. An effect of the deacetylation degree on the Huggins viscosity constant related to polymer solvent interaction is found. The most important results refer to the activation energy of viscous flow found from Arrhenius plots. The dependence of the activation energy on solution concentration, shear rate and DD is discussed.
Magnesium chloride supported bis(cyclopentadienyl)titanium(IV) dichloride‐MAO catalyst for ethylene polymerization
Authors: Sarma Soumen Sen , Sivaram Swaminathan
Published: April 2003

A novel magnesium chloride supported titanocene catalyst was synthesized using a soluble tetrahydrofuran complex of magnesium chloride. The suported catalyst polymerized ethylene with high activities in presence of methylaluminoxane. The significant feature of the supported metallocene catalyst is that it shows high polymerization activity at low Al/Ti ratio and at higher temperatures compared to soluble catalyst. The role of support in stabilizing the active species on the metallocene is discussed.
γ‐Ray‐induced post‐polymerization of a mesogenic methacrylate in the crystalline, liquid crystalline and melt phase: Reaction kinetics and molecular weight distribution
Authors: Hohn Wilfried , Beizai Kaweh , Tieke Bernd
Published: April 2003

The γ‐ray‐induced post‐polymerization of mesogenic 4‐methoxy‐4′‐(6‐methacryloyloxyhexyloxy)biphenyl (1) was investigated. Reaction kinetics and molecular weight distribution of the polymer were studied. Molecular weights and weight distributions were analyzed using size exclusion chromatography. Especially, effects of radiation dose, polymerization time and temperature were investigated. Post‐polymerization was found in the crystalline, liquid crystalline and melt phase. Rate of polymerization and limiting conversion to polymer increase with radiation dose, polymerization time and temperature. Samples exposed to a low γ‐ray dose of 5 kGy and subsequently polymerized in the crystalline state at 20°C, for example, only reach a limiting conversion of about 7% within 100 h, while samples exposed to a high dose of 20 kGy and polymerized in the melt at 79°C reach a limiting conversion of 85.1% within 90 s. Molecular weights increase with polymerization temperature and reach values comparable with in‐source polymerization. Different from in‐source polymerization, they are additionally affected by the parameters radiation dose and polymerization time. High molecular weights are obtained, if samples are exposed to a low radiation dose and isothermally polymerized at high temperature for a long time, while low molecular weights result from high radiation dose and short time of polymerization at low temperature, e.g., at 20°C. By carefully adjusting the reaction parameters, molecular weights can be reliably tailored in the range from 2 × 104 to 6 × 105. Polymerization at room temperature leads to a normal molecular weight distribution, while distributions are broader when the polymerization is carried out in the liquid crystalline or melt phase. The origin of the different reaction rates and molecular weights obtained under the various conditions is discussed in terms of the mobility of growing chain ends and residual monomer, which influences chain growth and termination and thus the kinetic chain length.
Formation of supramolecular aggregates by hydrogen bonding based on bispyrimidine and bisbarbituric acid
Authors: Wang Zhiqiang , Wang Liyan , Zhang Xi , Shen Jiacong , Denzinger Steffen , Ringsdorf Helmut
Published: April 2003

Hydrogen bonds between bispyrimidine and bisbarbituric acid in equal molar ratio can lead to the formation of supramolecular aggregates. This is established by TEM, IR and DSC measurements. Additionally, WAXS pattern showed that the aggregate is of laminar structure. Both the hydrolysis of this system and termination of the aggregate's growth were studied.
The X‐ray determination of the amounts of the phases in samples of isotactic poly(propylene) quenched from the melt at different cooling rates
Authors: Martorana Antonino , Piccarolo Stefano , Scichilone Francesco
Published: April 2003

A new procedure for the determination of the amounts of phases in samples of isotactic poly(propylene) quenched at different cooling rates from the same melted polymer is described. According to the procedure, all the patterns corresponding to the same quenching series are simultaneously analyzed for the amounts of phases so that reliable phase fractions relative to the different samples of the series are achieved. The analysis of the results points out that for increasing cooling rates above 30°C/s a remarkable increase of the mesomorphic phase settles, mainly at the expense of the α‐monoclinic one.
Synthesis and characterization of α‐hydroxy, α‐thiol and α‐chloroformyl oligomers of poly(butylene terephthalate)
Authors: Boutevin Bernard , Khamlichi Mohammed , Lusinchi Jean Marie , Robin Jean‐Jaques
Published: April 2003

α‐Hydroxy and α‐chloroformyl oligomers of poly(butylene terephthalate) (PBT) were prepared in 1,1,2,2‐tetrachloroethane by condensing terephthaloyl chloride and 1,4‐butanediol and using benzoyl chloride and 4‐hydroxybutyl benzoate as chain limitator. The average molecular weight was determined by 1H NMR analysis, and thermal properties were assessed by differential scanning calorimetry (DSC). Preparation of α‐thiol oligomers of PBT was also investigated by esterification of α‐hydroxy oligomers with thioglycolic acid and using p‐toluenesulfonic acid as catalyst. The DSC and TGA analyses pointed out that the introduction of a thiol group by esterification has no influence on the thermal properties of the PBT oligomers.
Structure and physicochemical properties of the aldol and vinylene forms of poly(2,5‐heteroarylenevinylene)s
Authors: Kreja Ludwik , Kurzawa Marzana , Kurzawa Jacek
Published: April 2003

We determined the structure and physicochemical properties of poly(2,5‐furylenevinylene), poly(2,5‐thienylenevinylene) and poly(2,5‐furylene‐co‐2,5‐thienylenevinylene) that were synthesized via aldol polycondensation. Two kinds of polymer were obtained, one with mainly aldol and one with mainly vinylene structure units. The former are soluble in water, and the latter insoluble in water and only slightly soluble in organic solvents. The aldol polymers can be transformed to vinylene polymers by thermal dehydration. The d.c. conductivities at room temperature are of the order of 10−12 and 10−8 S/cm for the aldol and vinylene forms, respectively.
γ‐Ray polymerization of lyotropic solutions of cellulose derivatives under retention of the macroscopic order
Authors: Hohn Wilfried , Tieke Bernd
Published: April 2003

Two new lyotropic solutions of cellulose derivatives are reported which can be polymerized upon γ‐irradiation. The first solution consists of hydroxypropylcellulose (HPC) in N,N‐dimethylacrylamide (DMAcr) and the second of 2‐(acryloyloxy)propylcellulose (APC; degree of substitution (DS) = 0.18) in water. Both solutions were characterized using refractive index measurements, polarizing microscopy and diffuse reflection spectroscopy. For solutions of HPC in DMAcr, it was demonstrated that they exhibit anisotropic phase behaviour at concentrations higher than 45 wt.‐% within a limited temperature range. Highly concentrated solutions of about 70 wt.‐% also showed cholesteric phase behaviour with iridescent colours. Upon γ‐irradiation, the solvent DMAcr rapidly polymerized. A conversion to 90% of polymer was reached at a dose of 5 kGy. Molecular composites of HPC in polymerized DMAcr were obtained in which the macroscopic order was preserved. Shear‐deformed samples were still birefringent and exhibited band textures, when viewed between crossed polarizers, and light reflection of the cholesteric samples still occurred at the same wavelength as before irradiation. The polymerized samples showed an extended temperature stability, the anisotropy being stable up to approximately 150°C. The second solution of APC in water also exhibits cholesteric phase behaviour at a concentration of 61.5 wt.‐%. Upon γ‐irradiation, the polymer chains undergo rapid cross‐linking via the reactive acrylate groups and form a network in which the cholesteric order is preserved. The cross‐linked APC films are swellable in water and retain their anisotropic order when the concentration of the solution is varied between 40 and 100 wt.‐% of APC. The materials properties of the two systems after polymerization are compared.
Synthesis and characterization of aliphatic‐aromatic poly(ether amide)s
Authors: García José M. , Álvarez Julio C. , De la Campa José G. , De Abajo Javier
Published: April 2003

Four aromatic diamines containing aliphatic spacers and Meta and para oriented oxyphenylene rings, and their corresponding hydrochlorides, were combined with isophthaloyl chloride (IPC) and terephthaloyl chloride (TPC) to give high molecular weight polyamides by interfacial and low‐temperature solution methods. The synthesis and characterization of monomers and polymers are reported, and the differences observed in polycondensation yields, molecular weights and molecular weight distributions, as a function of the method of synthesis, are discussed. Values of number‐average molecular weight (M̄n) up to 8 × 104 g/mol and weight‐average molecular weight (M̄w) up to 1 × 105 g/mol could be measured by gel permeation chromatography using aromatic polyamide standards, and values of M̄n up to 2 × 105 g/mol and M̄w up to 3.6 × 105 g/mol by using polystyrene standards.
Preparation and polymer‐analogous reactions of a poly(vinyl sugar) with a CC bond between sugar and polymer backbone
Authors: Wulff Günter , Bellmann Susanne , Schmid Jürgen , Podzimek Stepán
Published: April 2003

The synthesis of a new type of poly(vinyl sugar) is described whose polymer backbone is connected with the monosaccharide unit by a C—C bond. Such polymers can be obtained by radical initiation. They show good stability in polymer‐analogous reactions in contrast to common poly(vinyl saccharides) whose sugar residues are bound to the polymeric chain by ester, ether, or glycoside bonds. Starting from 7,8‐dideoxy‐1,2;3,4‐di‐O‐isopropylidene‐α‐D‐galacto‐oct‐7‐en‐1,5‐pyranos‐6‐ulose (1) polymers (P1) could be obtained by emulsion polymerization in high yields. Reduction of the keto group of P1 proceeded quantitatively and yielded poly(7,8‐dideoxy‐1,2;3,4‐di‐O‐isopropylidene‐D,L‐glycero‐α‐D‐galacto‐oct‐7‐en‐1,5‐pyranose) (P3). In contrast to the following polymers without protecting groups these poly(vinyl ketones), which were soluble in tetrahydro‐furan and toluene, did not follow a pure GPC‐separation mechanism. The protecting groups of the poly(vinyl saccharides), either with or without keto groups, could be removed completely to give P2 and P4. The solubility of the polymers P2 with galactose‐functionalized side chains in water was limited to a weight‐average molecular weight M̄w of 1 500 000 due to association phenomena of the monosaccharide units. Reduction of the hemiacetal group and of the keto group of P2 yielded poly(1,2‐dideoxy‐D,L‐glycero‐D‐galacto‐oct‐1‐enitol) (P5) with sugar alcohol side chains instead of a cyclic monosaccharide unit. Oxidation of the hemiacetal group of P2 and P4 furnished poly(7,8‐dideoxy‐D‐galacto‐oct‐7‐en‐6‐ulosonic acid sodium salt) (P6) and poly(7,8‐dideoxy‐D,L‐glycero‐D‐galacto‐oct‐7‐enonic acid sodium salt) (P7), respectively. These polymers showed very high viscosities because of their polyelectrolyte character.
Difference in propagation rate constants between photo‐and thermal‐initiated polymerization of styrene – effects of light irradiation
Authors: Kamachi Mikiharu , Kajiwara Atsushi
Published: April 2003

Propagation rate constants (kp) for photo‐ and thermal‐initiated radical polymerizations of styrene were determined by electron spin resonance (ESR) spectroscopy. The kp value for the former at 70°C ((420 ± 30) M−1 · S−1) was more than twice as large as that for the latter ((190 ± 10) M−1 · s−1) although the former value was almost the same as that obtained with the pulsed‐laser polymerization method. To evaluate the origin of the difference in the kp values between photo‐ and thermal‐initiated polymerization the absorption spectrum of a model of the propagating radical was measured and both the influence of the wavelength of the irradiation light on kp values and the activation energy of the photo‐initiated radical polymerization of styrene were determined. kp decreases for wave‐lengths shorter than 370 nm and is in agreement with the kp value for thermal‐initiated polymerization. No wavelength dependence of kp was obtained for dienes whose propagating radical does not absorb above 300 nm. The difference in kp values for photo‐ and thermal‐initiated polymerizations is considered to be due to the photoactivation (photoinduced excitation) of the propagating radical of styrene.
Synthesis and properties of aromatic polyamides based on 4,4′‐(1,5‐naphthalenedioxy)dibenzoic acid
Authors: Hsiao Sheng‐Huei , Chu Kuan‐Yu
Published: April 2003

4,4′‐(1,5‐Naphthalenedioxy)dibenzoic acid (3), a novel aromatic dicarboxylic acid monomer, was prepared by nucleophilic substitution reaction of 1,5‐dihydroxynaphthalene and p‐fluorobenzonitrile in N,N‐dimethylformamide (DMF) in the presence of potassium carbonate and subsequent alkaline hydrolysis of the intermediate dinitrile, 4,4′‐(1,5‐naphthalenendioxy)dibenzonitrile. Using triphenyl phosphite (TPP) and pyridine as condensing agents, a series of novel aromatic polyamides were synthesized by direct poly‐condensation of diacid 3 and twelve aromatic diamines in N‐methyl‐2‐pyrrolidone (NMP) solution containing dissolved calcium chloride. The resulting polyamides had inherent viscosities above 1,14 and up to 4,45 dL/g. Most of these polyamides are readily soluble in polar solvents, such as NMP, DMF, and N,N‐dimethylacetamide (DMAc). Transparent, flexible, and tough films could be cast from their DMAc or NMP solutions. Most of these polymers were amorphous in nature, as indicated by their wide‐angle X‐ray diffractograms. Thermogravimetric analysis (TG) showed that all the polyamides were stable up to 450°C in both air and nitrogen atmosphere. Most of them revealed a distinct glass transition on the differential scanning calorimetry (DSC) traces in the range of 183–259°C.
Synthesis of methacrylic multi‐arm star copolymers by “arm‐first” group transfer polymerisation
Authors: Haddleton David M. , Crossman Martin C.
Published: April 2003

Methacrylic star polymers were synthesized by the “arm‐first” method of star polymer formation by the addition of difunctional monomer, ethylene glycol dimethacrylate, to living linear poly(methyl methacrylate) as prepared by group transfer polymerisation (GTP). The effects of living polymer concentration and ratio of difunctional monomer to living polymer are discussed, and show how macromolecular design and control may be imposed on the number of arms and molecular weight of the star polymer. Diluting the difunctional crosslinking monomer with monomer has been examined with the view to establishing funtionalisation of the star core.
Differential scanning calorimetry studies on water restrained in hydroxyethylcellulose and hydrophobically modified hydroxyethylcellulose
Authors: Tanaka Ryohei , Hatakeyama Tatsuko , Hatakeyama Hyoe
Published: April 2003

Differential scanning calorimetric (DSC) studies were carried out for hydrophobically modified hydroxyethylcellulose (HMHEC)‐ and hydroxyethylcellulose (HEC)‐water systems to examine the binding of water with polymer molecules and the formation of a structure. The amount of freezing‐bound water in HMHEC was found to be much less than that in HEC. The above fact suggests that the water‐polymer interaction is hindered by the presence of the hydrophobes. The formation of a structure above the melting point of ice was detected by DSC for both systems HMHEC‐ and HEC‐water. Polarizing light micrographs of these two aqueous polymer systems showed the formation of a liquid crystalline state in the same range of temperature. These phenomena were observed in a wider range of water content for HMHEC (Wc <4.0) than for HEC (Wc <2.5).
Association and surface properties of diblock copolymers of ethylene oxide and DL‐lactide in aqueous solution
Authors: Tanodekaew Siriporn , Pannu Rachpal , Heatley Frank , Attwood David , Booth Colin
Published: April 2003

Diblock copolymers of ethylene oxide and DL‐lactide (EmLn copolymers) were prepared by sequential anionic polymerisation and characterised by gel permeation chromatography (GPC) and 13C NMR. Their association and surface properties in aqueous solution were studied by surface tension and dynamic and static light scattering. Comparison of the critical micelle concentrations (cmc) and micelle association numbers (Nw) of the EmLn copolymers with published values for oxyethylene/oxybutylene (EmBn) copolymers indicated a slightly lower hydrophobicity for a lactide unit: i.e. L ≃ 0.75B. The temperature dependence of the cmc of copolymer E42L12 was analysed to obtain a standard enthalpy of micellisation ΔmicH0 ≈ 40 kJ · mol−1.
Luminescence quenching of partially quaternized poly(1‐vinylimidazole)‐bound ruthenium(II) complex in methanol
Authors: Suzuki Masahiro , Mori Yoshiaki , Yokoyama Naoki , Kimura Mutsumi , Hanabusa Kenji , Shirai Hirofusa
Published: April 2003

Metallopolymers in which bis(2,2′‐bipyridine)ruthenium(II) complexes are coordinated to imidazolyl residues on partially quaternized poly(1‐vinylimidazole) having different degree of quaternization (RuQPIm) were synthesized. The luminescence quenching of the photoexcited RuQPIms with various alkylviologens having different length of alkyl group was investigated in MeOH. In quenching of RuQPIm with methylviologen (MV2+), the efficiency of quenching decreases with increasing degree of quaternization. This was attributed to the electrostatic repulsion between the MV2+ species and the quaternized imidazolium residue on the polymer backbone and steric hindrance of the alkyl side chain. Furthermore, the efficiency of quenching depends on the length of the alkyl group in viologen. These results suggest that the alkyl side chain on the polymer backbone exerts steric hindrance at low degree of quaternization and van der waals interaction at high degree of quaternization.
The crystal structure and drawing‐induced polymorphism in poly(aryl ether ketone)s, 2. Poly(ether ether ketone ketone), PEEKK
Authors: Wang Shanger , Wang Junzuo , Liu Tianxi , Mo Zhishen , Zhang Hongfang , Yang Decai , Wu Zhongwen
Published: April 2003

The crystal structure, morphology and polymorphism induced by uniaxial drawing of poly(ether ether ketone ketone) [PEEKK] have been studied by transmission electron microscopy (TEM), electron diffraction (ED) and wide angle X‐ray diffraction (WAXD). On the basis of WAXD and ED patterns, the crystal structure of unoriented PEEKK is determined to have two‐chain orthorhombic packing with unit cell parameters of a = 0.772 nm, b = 0.600 nm, c = 1.004 nm (form I). A stress‐induced crystal modification (form II) is identified and found to possess a two‐chain orthorhombic lattice with unit cell dimensions of a = 0.461 nm, b = 1.074 nm, c = 1.080 nm. The 7.5% increase in c‐axis dimension for form II is attributed to an overextended chain conformation, arising from extensional deformation during uniaxial drawing and fixed “in‐situ” through strain‐induced crystallization. The average ether‐ketone bridge bond angles in form II crystal are determined to be 148.9° by using standard bond lengths. The crystal morphology of PEEKK bears a great similarity to that of PEEK. The crystals grow in the form of spherulites and have the b‐axis of unit cell radial. The effects of draw rate on strain‐induced crystallization and induction of form II structure are also discussed.
Biodegradable drug carriers based on poly(ethylene glycol) block copolymers
Authors: Pechar Michal , Strohalm Jiří , Ulbrich Karel , Schacht Etienne
Published: April 2003

The synthesis of a model water‐soluble drug carrier system based on poly(ethylene glycol) (PEG) block copolymers is described. In the system, two blocks of PEG are connected via a biodegradable oligopeptide or amino acid linkage incorporating at least one glutamic acid residue. A drug model (4‐nitroaniline) is attached to the γ‐carboxyl group of glutamic acid of the polymer carrier via an enzymatically degradable oligopeptide spacer. All oligopeptides were prepared as potential substrates for cathepsin B, a representative of lysosomal enzymes. The relationship between the structure of oligopeptides forming the linkage between two PEG molecules and the rate of cathepsin B‐catalyzed polymer chain degradation is evaluated. The relationship between the structure of the spacer and kinetics of drug model release from the carrier after incubation in cathepsin B solution is also discussed in detail. The results show that, by altering the structure of oligopeptides in the polymer construct, marked changes in the rate of both polymer degradation and the drug model release can be achieved.
Melting behavior of poly(3‐alkylthiophene)s with long alkyl side‐chains
Authors: Zhao Yue , Keroack Daniel , Yuan Guoxion , Massicotte André , Hanna Roula , Leclerc Mario
Published: April 2003

The melting behavior of two non‐oriented poly(3‐alkylthiophene)s (P3ATs) containing 12 and 14 carbon atoms, respectively, in the alkyl side chain was investigated by means of differential scanning calorimetry. We show that the two P3ATs display three melting endotherms after an isothermal annealing from the melt. Two of the melting peaks arise from the ordered structures which are completed in the course of the quenching of the sample from the melt, and judging from the essentially constant melting temperatures and heats of fusion, they are not influenced by the subsequent isothermal annealing conditions. On the other hand, a much slower crystallization induced by the annealing, which occurs over a wide range of temperatures, is responsible for the appearance of a third melting endotherm which is strongly dependent on the crystallization condition. We show that this secondary crystallization is not a perfection of the existing ordered structures, rather it results in distinct crystals which melt at a temperature Tm slightly above the crystallization temperature Tc. Moreover, it is shown that the plot of Tm versus Tc parallels the line of Tm = Tc, and that the difference Tm − Tc increases linearly as the number of carbon atoms in the side chain decreases. On the basis of the calorimetric and X‐ray diffraction measurements, it is suggested that the secondary crystallization originates from the alkyl side chains.
Synthesis of a new polymer — polycyclopentylenevinylene bearing ge‐containing group
Authors: Finkelshtein Eugene Sh. , Portnykh Elena B. , Ushakov Nikolai V. , Gringolts Maria L. , Yampolsky Yury P.
Published: April 2003

A new polymer, poly[5‐(trimethylgermylmethyl)‐1,3‐cyclopentylenevinylene], was synthesized via ROMP of 5‐(trimethylgermylmethyl)‐2‐norbornene in the presence of RuCl3 · 3H2O, RuCl3(PPh3)3 and RuCl2(PPh3)3 catalysts. The structure of the synthesized polymer was determined on the basis of IR, 1H NMR and 13C NMR spectra. The gas transport properties for this polymer have been studied.