bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis of methyl methacrylate/styrene copolymer bearing a carbomethoxyallyl end group with limited molecular weight by addition‐fragmentation reaction of methyl α‐(bromomethyl)‐acrylate
Authors: Yamada Bunichiro , Kobatake Seiya , Aoki Shuzo 
Published: April 2003

AbstractThe synthesis of methyl methacrylate/styrene copolymer bearing overwhelmingly bromine and the 2‐carbomethoxyallyl group (CH2C(COOCH3)CH2) at the α‐ and ω‐termini instead of the fragment of the initiator with reduced molecular weight was investigated by using methyl α‐(bromomethyl)acrylate as chain transfer agent through the addition‐fragmentation mechanism. The molecular weight of the copolymer was effectively decreased with bromomethylacrylate, and the unsaturated end groups quantitatively bound to two types of the monomeric units were differentiated by means of 1H NMR spectroscopy. Equations estimating the reactivities of methyl α‐(bromomethyl)acrylate towards polystyrene and poly(methyl methacrylate) radicals were derived. Methyl α‐(bromomethyl)acrylate was found to be more reactive toward the poly(methyl methacrylate) radical than the polystyrene radical by a factor of 0,62.
Radical polymerization of ring‐substituted trans‐cinnamonitriles and formation of ladder spin polymer
Authors: Tanaka Hitoshi , Kikukawa Yoshimasa , Sataki Maki , Sato Tsuneyuki , Ota Tadatoshi 
Published: April 2003

AbstractThe polymerization of ring‐substituted trans‐cinnamonitriles has been studied with radical initiators such as peroxides and azo compounds at 60–130°C. 3,4,5‐Trimethoxycinnamonitriles (3,4,5‐MOCN) yield a homopolymer with a molecular weight of about 104 in contrast to the unsubstituted cinnamonitrile. The activation energy of the 3,4,5‐MOCN polymerization is 106 kJ/mol and the polymerization rate is proportional to the 0,45th power of the initiator concentration. Radical copolymerization of 3,4,5‐MOCN yields copolymers with vinyl monomers such as styrene and acrylonitrile. ESR studies suggested that the primary radical from an azo initiator attacks at the olefinic carbon of the cinnamonitrile bearing the cyano group. Heating of the 3,4,5‐MOCN homopolymer produces a ladder spin polymer with hydroaniline units in the main chain.
Multicolor electrochromic behavior of polyaniline composite films combined with tungsten trioxide
Authors: Morita Mitsuyuki 
Published: April 2003

AbstractThe electrochromic behavior of polyaniline‐poly(vinyl alcohol) composite films (CPAn‐PVA) combined with an electrochemically synthesized tungsten trioxide film (WO3) was investigated in LiClO4CH3CN aprotic non‐aqueous solution. The combination was achieved by chemical deposition of CPAn‐PVA on WO3. The combined film shows an electrochromic behavior roughly identical with the sum of the behaviors of each component material. The color change of the combined film from blue to green in the cathodic region is of lower contrast in comparison with that expected from the combination. From ex‐situ FT‐IR spectroscopy it became clear that the weakened electrochromic change is due to some interaction between polyaniline and WO3. However, this interaction also activates the electrochemical oxidation process of polyaniline. As a result, the combined film shows a color change owing to the oxidation of polyaniline applying much lower potential than for CPAn‐PVA. This suggests the possibility of construction of electrochromic devices with high electrochemical stability operating at low potentials.
Particle growth in butadiene emulsion polymerization, 2. Gamma radiolysis
Authors: Verdurmen Edwin M. , German Anton L. , Sudol E. David , Gilbert Robert G. 
Published: April 2003

AbstractThe kinetics of the emulsion polymerization of butadiene at 60°C in Smith‐Ewart interval III were investigated using gamma radiation to produce initiating species. The aim of this work was to determine radical desorption rate coefficients through monitoring non‐steady state kinetics. The acquired data of the average number of radicals per particle (n) were in good agreement with data obtained from chemically initiated experiments. It was shown that the approach to steady state is kinetically determined and that thermal background initiation is negligible in the butadiene emulsion polymerization. While radical desorption rate coefficient data was determined with high uncertainty, the results are consistent with the transfer diffusion mechanism of radical exit.
Particle growth in butadiene emulsion polymerization, 3. Radical adsorption and desorption rate coefficients
Authors: Verdurmen Edwin M. , Geurts John M. , German Anton L. 
Published: April 2003

AbstractThe kinetis of the emulsion polymerization of butadiene at 60°C in Smith‐Ewart interval III were investigated using peroxodisulfate as initiator. The aim of this work was to obtain insight in the radical adsorption and desorption rate coefficients through monitoring non‐steady state kinetics. The acquired data shows an initiator concentration dependence of the desorption rate coefficients. This dependence explains the independences of the rate of butadiene emulsion polymerization of the peroxodisulfate concentration in the presence of tertiary dodecylthiols.
Influence of ageing on the ordering phenomena of syndiotactic polystyrene
Authors: de Candia Francesco , Russo Roberto , Vittoria Vittoria 
Published: April 2003

AbstractThe crystallization from the glassy state of different samples of syndiotactic polystyrene (sPS) was investigated with different techniques, such as differential scanning calorimetry, infrared analysis, and polarized optical microscopy. The different samples of sPS were obtained by ageing the glassy sPS films at room temperature and at 70°C; the behaviour of these films was compared with that of the fresh sample, put at the crystallization temperature as soon as prepared. The temperature of crystallization was 120°C; at this temperature, besides the crystalline phase, a fraction of mesophase is formed. All the techniques investigated to follow the crystallization phenomenon show that the fresh sample crystallizes much sooner than the others; the sample aged at 70°C takes the longest time to crystallize, whereas an intermediate behaviour characterizes the sample aged at room temperature. This result was correlated with the initial structural organization of the glassy amorphous samples.
The system methylcyclohexane/polystyrene. Experimental critical curves, cloud‐point and spinodal isopleths, and their description with a semi‐phenomenological treatment
Authors: Vanhee Sabine , Kiepen Friedheinz , Brinkmann Dirk , Borchard Werner , Koningsveld Ronald , Berghmans Hugo 
Published: April 2003

AbstractCloud‐point and spinodal pressures up to 900 bar were investigated for the system methylcyclohexane/polystyrene using a pressure‐pulse‐induced scattering technique based on the theory of Debye. The molar‐mass range of the polymer samples is 9–50 kg/mol. The values determined isothermally in a large concentration range for a polymer sample with weight‐average molar mass Mw = 17,5 kg/mol lead to isopleths which allow the construction of phase diagrams displaying cloud‐point and spinodal curves (in terms of temperature or pressure against concentration). Critical isopleths have been determined for three further samples with Mw = 9,0, Mw = 28,5 and Mw = 50,0 kg/mol. A semi‐phenomenological treatment of the data is presented which allows an accurate description of experimental phase diagrams and isopleths for one single sample (PS 17,5). A prediction of the critical P(T) curves for the other samples, of different average molar mass, then fails completely. Fitting the model parameters to the critical data of all four samples improves the description of the critical curves but produces phase diagrams showing considerable deviations from the data. One reason for the failure of the model may be sought in its inherent incapability to deal with dilute polymer solutions in which the individual coils are separeated by regions of pure solvent. A first rough attempt to deal with this effect already brings a marked improvement in the agreement between experiment and model calculation for the critical curves, albeit at the cost of introduction of a number of adaptable parameters.
Study of polystyrene‐block‐poly(methyl methacrylate) micelles by size exclusion chromatography/low‐angle laser light scattering, 1. Influence of copolymer concentration and flow rate
Authors: Grubišć‐Gallot Zlatka , Gallot Yves , Sedláček Jan 
Published: April 2003

AbstractA size exclusion chromatography study of the micellar system polystyrene‐block‐poly(methyl methacrylate) in the mixed solvent 1,4‐dioxane/cyclohexane is reported. Good separation of the peaks of micelles enabled direct determination of the weight‐average molecular weights of micelles with a low‐angle laser light scattering detector. The values obtained were found to be in accordance with those determined independently by static light scattering. Experiments with changing flow rate and concentration of the injected sample solution show moderately fast unimer‐micelles re‐equalibration in the course of the separation. A strong effect of the solute trapping in the column, probably due to the adsorption of the unimer on the packing, was observed.
Rate constants for elementary reactions of the radical polymerization of methyl 2‐(benzyloxymethyl)acrylate as polymerizable acrylate bearing large substitutents
Authors: Yamada Bunichiro , Kobatake Seiya , Aoki Shuzo 
Published: April 2003

AbstractMethyl 2‐(benzyloxymethyl)acrylate (MBZMA) which was synthesized by reaction of methyl 2‐(bromomethyl)acrylate with benzyl alcohol was radically homo‐ and copolymerized. MBZMA polymerized as fast as methyl methacrylate despite of the presence of a large 2‐substituent. The absolute rate constants for propagation and termination were evaluated from the direct determination of the steady state concentration of the propagating radical by electron spin resonance spectroscopy at 60°C: kp = 182 dm3 · mol−1 · s−1 and kt = 1,6 · 106 dm3 · mol−1 · s−1. It was deduced from the magnitude of the rate constants that the balance of the slow propagation and termination allows the formation of a polymer. Evaluation of the cross‐propagation rate constants in the copolymerization with styrene revealed that primarily the steric effect of the benzyloxymethyl group reduced the reactivity of the polymer radical and that the electronwithdrawing character of the 2‐substituent prevailing the steric effect enhanced the monomer reactivity toward the polystyrene radical.
Fluorescence spectra of polybenzamide in isotropic and nematic solutions
Authors: Bai Fenglian , Zhang Shufan , Yang Junlin , Qian Renyuan 
Published: April 2003

AbstractThe fluorescence spectra of polybenzamide (PBA) in N,N‐dimethylacetamide with 3% LiCl (A) and in 98% H2SO4 (B) solutions have been studied both in very dilute and in nematic solutions. Stacked chromophores of PBA play an important role in the formation of nematic phase. Fluorescence intensity from solution A is much higher than that from solution B under the same conditions of excitation. Differences in the fluorescence behavior of solutions A and B are discussed in regard of the monochromophore emission and monochromophore excitation and long wavelength emission. Fluorescence emission has been shown to be an extremely sensitive tool to probe some molecular species present in minute amounts, which show up readily in the excitation spectrum of fluorescence emission but escape from detection in the absorption spectrum.
Initiation and propagation reactions in the copolymerization of epoxide with carbon dioxide by catalysts based on diethylzinc and polyhydric phenol
Authors: Kuran Witold , Listoś Tomasz 
Published: April 2003

AbstractPropylene oxide and cyclohexene oxide were copolymerized with carbon dioxide in the presence of catalysts such as diethylzinc with phenol or 1‐phenoxy‐2‐propanol and/or a polyhydric phenol (polyhydroxybenzene derivatives such as 4‐tert‐butylcatechol, pyrogallol): The corresponding copolymers with predominant carbonate linkages and the respective cyclic alkylene carbonates as by‐products were obtained in the presence of catalysts derived from diethylzinc and polyhydric phenol. Cyclic alkylene carbonates but no polymeric products were formed in the presence of catalysts derived from diethylzinc and monoprotic compound. The copolymers were analysed by means of 1H‐ and 13C nuclear magnetic resonance (NMR) spectroscopy in terms of chain microstructure and end groups. Alkaline hydrolysis of the cyclohexene oxide/carbon dioxide copolymer was performed and the trans‐structure of the obtained cyclohexane‐1,2‐diol was determined. Mechanisms for the initiation and propagation reactions are proposed and discussed.
Photodegradation of poly[ethylene‐co‐propene‐co‐(5‐ethylidene‐2‐norbornene)] rubbers, 1. Reappraisal of the photo‐oxidation mechanism under accelerated conditions
Authors: Scoponi Marco , Pradella Fiorella , Carassiti Vittorio , Tartari Davide 
Published: April 2003

AbstractIn this work the reexamination of the photo‐oxidation mechanism of three poly(ethylene‐co‐propene‐co‐5‐ethylidene‐2‐norbornene) (EPDM) terpolymers containing different amounts of 5‐ethylidene‐2‐norbornene (ENB)System. name: 5‐ethylidenebicyclo[2.2.1]hept‐2‐ene.
(2‐8 wt.‐%) is discussed. The photo‐oxidation depends on the initial content of ENB units in the chains. The formation of a band at 923 cm−1 is attributed to the CH out‐of‐plane deformation of a new double bond in terminal position in the ethylidene moieties. The presence of double bond migration suggests the formation of stable tertiary hydroperoxides which show a new band at 870 cm−1. The kinetic behaviour of a band with similar spectral pattern in the UV at 235 nm has been correlated with double bond migration. The identification of photoproducts both by 2,4‐dinitrophenylhydrazin and SO2 confirms the proposed spectroscopic assignments. The gel measurements of the studied terpolymers, and some comparisons with a poly(ethylene‐co‐propene) (EPR) copolymer having a similar ethylene to propene ratio, suggest that the presence of ENB can strongly influence both the photo‐oxidation and the crosslinking yields of these rubbers.
Degradation of poly(propylene carbonate) by coordination catalysts containing phenolatozinc and alcoholatozinc species
Authors: Kuran Witold , Listoś Tomasz 
Published: April 2003

AbstractPoly(propylene carbonate) was treated with coordination catalysts exhibiting activity in propylene oxide/carbon dioxide copolymerization and cyclization. Poly(propylene carbonate) was found to undergo degradation and depolymerization reactions which were monitored by intrinsic viscosity of the polymer and the yield of propylene carbonate. End‐groups in the degraded polymer were determined using ultraviolet spectroscopy. Catalysts containing active phenolatozinc species were shown to cleave the poly(propylene carbonate) chain introducing to it the aryloxy moiety as aryl carbonate end‐group and the zinc moiety as alcoholatozinc end‐group. On the contrary, catalysts containing active alcoholatozinc species were shown to cleave the poly(propylene carbonate) chain introducing to it the alcoholate moiety as alcoholate end‐group and the zinc moiety as alkylcarbonatozinc end‐group. Propylene carbonate formation was proposed to occur involving chain depolymerization via alcoholatozinc end‐groups. Propylene carbonate formation involving chains terminated with alkylcarbonatozinc groups was proposed to be preceded by their decarboxylation with CO2 elimination leading to alcoholatozinc end‐groups.
Stimuli‐sensitivities of hydrogels containing phosphate groups
Authors: Miyata Takashi , Nakamae Katsuhiko , Hoffman Allan S. , Kanzaki Yoshio 
Published: April 2003

AbstractThe effect of an introduction of phosphate groups into hydrogels on their stimuli‐sensitivities has been investigated. Several hydrogels containing various phosphate group content were synthesized via solution copolymerization of 2‐(methacryloyloxy)ethyl dihydrogen phosphate (Phosmer) and 2‐hydroxyethyl methacrylate (HEMA) in the presence of 2,2′‐azoisobutyronitrile (AIBN) in methanol at 70°C for 4 h. The content of phosphate groups incorporated into the resulting hydrogels ranged from 1 to 13 mol‐%. The swelling ratio of these hydrogels was found to be strongly affected by pH, solvent, temperature and phosphate group content. The polymersolvent interaction parameter χ of the hydrogel was determined from the Flory‐Rehner equation, using the swelling ratio and the crosslinking density derived from the compression modulus. Furthermore, χ was divided into its enthalpic (χH) and entropic component (χS). Using the interaction parameter, the stimuli‐sensitivity of the hydrogel is discussed in detail based on thermodynamic aspects.
Synthesis and characterization of polymers bearing pyrazole groups, 1. Methacrylic derivatives
Authors: Boutevin Bernard , Guida‐Pietrasanta Francine , Malek Fouad 
Published: April 2003

AbstractThe synthesis of new methacrylic monomers H2CC(CH3)COOCH2G where G is a pyridine, a pyrazole or a bipyrazole group has been achieved. Their homopolymerization was studied and gave fairly low molecular mass polymers. Their copolymerization with styrene gave copolymers tending to be alternating when the bulkiness of group G increased. Moreover, in the presence of Lewis acids the monomers were complexed. With ZnCl2, they were complexed through nitrogen atoms and were shown to be inactive in copolymerization. With SnCl4, they were complexed through the carbonyl group and gave alternating copolymers. The homopolymers exhibited low glass transition temperatures (50–76°C) and moderate thermal stability (decomposition begins at ca. 200–280°C and is complete at 550°C). In the copolymers with styrene the thermal properties showed to be improved.
Determination of the partial specific volumes of thermoreversible gelatin/water and κ‐carrageenan/water gels
Authors: Cöulfen Helmut , Borchard Werner 
Published: April 2003

AbstractIn this paper systematic density measurements of gelatin/water and κ‐carrageenan/water gels are presented in a wide range of concentrations and temperatures. From about 600 measurements for gelatin/water and about 500 measurements for the system κ‐carrageenan/water empirical relations for both systems have been derived which allow to calculate the densities of these gels in a limited concentration range if the temperatures and the polymer weight fractions are known. The calculated densities have an accuracy of better than 0,001 g/cm−3 compared with the directly measured densities. If the extrapolated partial specific volumes of the pure polymer are plotted against the temperature, a jump with an inflexion point can be detected at about 23–24°C for both systems. These data indicate a Λ‐type transition of the expansion coefficient α for both systems at 23–24°C although there are still too few data to make clear conclusions.
Effects of soft segments and hydrolysis on the crystallization behavior of degradable poly(oxyethylene)/poly(L‐lactide) block copolymers
Authors: Hu David Shiaw‐Guang , Liu Hsin‐Jiant 
Published: April 2003

AbstractThe crystallization behavior of poly(oxyethylene) (PEG)/poly(L‐lactide) (PLLA) block copolymers with PEG (number‐average molecular weights Mn = 1000–6000) contents ≦ 18,3 wt.‐% has been studied under different isothermal temperature and linear cooling conditions. A differential scanning calorimeter was used to monitor the energetics of the crystallization process from the melt state. The influence of copolymer composition and hydrolysis on radial growth rates of spherulites, G, in PEG/PLLA copolymer was investigated using polarized light video‐microscopy. The data were analyzed in terms of a model describing two processes, namely crystal nucleation and growth which were observed experimentally in a typical Avrami plot for the isothermal data. At a given crystallization temperature, G's are increased with increasing PEG content and with decreasing PEG segment length in PEG/PLLA copolymer spherulites. The Avrami exponent n and rate coefficient k of PEG/PLLA copolymers decrease with increasing hydrolysis time up to 200 h. The spherulite morphology appeared to be a complex function of copolymer composition, hydrolysis time and crystallization temperature.
Shear influence on the phase separation of oligomer blends
Authors: Muniz Edvani C. , Nunes Suzana P. , Wolf B. A. 
Published: April 2003

AbstractShear influences on the phase separation behaviour of four different blends of ethylene glycol/propylene glycol oligomers, exhibiting upper critical solution temperatures, were investigated. Cloud point curves at rest (turbidity measurements) are reported for all systems, spinodal conditions (light scattering) and tie‐lines (analysis of the coexisting phases) are given for some examples. Phase diagrams under shear were obtained from rheological data. They demonstrate that the demixing temperatures of systems where both glycols bear OH end‐groups are lowered up to ca. 1°C by shear rates of 1000s−1; the critical composition, generalized to the non‐equilibrium conditions of flow, is markedly shifted. These observations are explained in terms of the generalized Gibbs energy (containing the mechanical energy the system stores during flow) as a consequence of the strongly interacting end‐groups of the glycols. This interpretation is backed by the fact that the shear effects disappear when the glycols are methylated.
Liquid‐crystalline main‐chain polymers with a poly(p‐phenylene terephthalate) backbone, 8. Synthesis and characterization of polyesters with 3‐ethoxypropoxy and 6‐(pentyloxy)hexyloxy side chains
Authors: Mercx Frans P. M. , Tinnemans Alois H. A. , Damman Sebastiaan B. 
Published: April 2003

AbstractThe influence of replacing a methylene group in the middle of the side chain of alkoxy‐substituted poly(p‐phenylene terephthalate)s by an oxygen atom was investigated by differential scanning calorimetry (DSC), rheological measurements and X‐ray diffraction. Due to the presence of the oxygen atom the side chains of the polymer with long side chains (PTA12(O)HQ) lose their ability to crystallize. Except for this difference and a shift of the transition temperatures to lower temperatures, this polymer shows a similar phase behaviour compared to the corresponding alkoxy‐substituted polyester PTA12HQ. The polymer with short side chains, PTA6(O)HQ, shows a similar behaviour as the corresponding polymer without an extra oxygen atom, PTA6HQ. Only the transition to the nematic mesophase is shifted to lower temperatures.
Preparation of surface‐modified polystyrene microspheres by an azo‐initiator having analogous structure to the head group of phosphatidylcholine
Authors: Sugiyama Kazuo , Ohga Koji , Kikukawa Kiyoshi 
Published: April 2003

AbstractA novel azo‐initiator, 2‐[(2‐ethylphosphatoethyl)dimethylammonio]ethyl 4,4′‐azobis‐(4‐cyanovalerate) (EAP‐501), was prepared. EAP‐501 [m. p. 97°C (dec.), λmax 346 nm in H2O] was found to be amphiphilic, with a Krafft point of 11,5°C and a critical micelle concentration of 47,2 mmol·dm−3 at 30°C and 48,6 mmol·dm−3 at 70°C. The rate and activation parameters for the thermal decomposition of EAP‐501 at 70°C were estimated to be kd = 2,35·10−5 s−1, ΔH≠ = 118,4 kJ·mol−1 and ΔS≠ = 10,5 J·mol−1·K−1. Emulsion polymerization of styrene initiated with EAP‐501 gave polymer microspheres in high yield. The resulting polystyrene microspheres were characterized by transmission electron microscopy (TEM) and X‐ray photoelectron spectroscopy (XPS). The polystyrene microspheres have diameters from 321 to 649 nm by varying the EAP‐501 concentration. The ammonium phosphate groups, which are comparable to the polar head group of phospholipids, are concentrated on the surface of the particles. The particles were found to reduce the adsorption of bovine serum albumin (BSA) compared with particles prepared by the emulsion polymerization of styrene initiated with potassium persulfate as an initiator.