bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis of styrene–isoprene A2B2 hetero‐armed star copolymers
Authors: Wright Simon J. , Young Ronald N. , Croucher Terence G. 
Published: April 2003

AbstractStyrene–isoprene A2B2 star copolymers having two arms of polystyrene and two of polyisoprene have been synthesised. Two routes have been followed. In the first, 2 moles of polydienyl lithium were coupled, without loss of carbanionic character, by reacting with 1 mole of 1,3‐bis(1‐phenylethenyl) benzene. The difunctional adduct was then used to initiate the polymerisation of styrene in the presence of a small amount of triethylamine which served to ensure a rapid crossover. In the second route, 2 moles of polystyrl lithium were coupled with 1 mol of SiCl4 in benzene; no attendant formation of three‐armed star was detected. Introduction of large excess of polyisoprenyl lithium, together with triethylamine as catalyst, generated the star which was isolated by fractional precipitation.
Relative reactivities and graft distributions of polystyrene Macromers® in vinyl chloride copolymerization
Authors: Schulz Gerald O. , Milkovich Ralph 
Published: April 2003

AbstractPolystyrene macromonomers terminated with methacrylate, vinyl ether, or maleic half ester functionalities were evaluated in free radical initiated copolymerizations with vinyl chloride in aqueous suspension polymerization. Macromers® (M1) terminated with methacrylate disappeared very rapidly in copolymerization with vinyl chloride (M2). The relative reactivity ratio, r2, was determined to be 0.05 in good agreement with literature values of about 0.04. Vinyl ether‐terminated Macromers® had unexpectedly uniform reactivity with vinyl chloride in early conversion samples, but macromonomer conversion was incomplete. Macromers® having maleic half ester functionality were incorporated rapidly in vinyl chloride copolymerization at pH 2.5 (r2 = 0.13). However, at pH 10 these Macromers® had reduced reactivity (r2 = 0.34), which improved graft polymer uniformity. These Macromer® copolymerization relative reactivities are shown to be useful in predicting and controlling graft densities and graft polymer heterogeneity which influence morphology, processing, and mechanical properties.
Rates of carbonate bond formation: Implications for macrocyclization
Authors: Aquino Eugene , Brittain William J. , Brunelle Daniel J. 
Published: April 2003

AbstractHigh yields of cyclic oligomeric carbonates can be prepared using an amine‐catalyzed reaction of bisphenol A–bischloroformate. We have studied the mechanistic aspets of this carbonate macrocyclization by the isolated study of key chemical events. Using stopped‐flow FT‐IR spectroscopy, we have found that the rate of carbonate formation between the intermediate acyl ammonium salt and 4‐isopropylphenol is the same for the acyl ammonium salt derived from tri‐n‐butylamine, triethylamine and diethylmethylamine. Previously, we found that conversion of acyl ammonium salt to urethane was also insensitive to amine structure while the formation of acyl ammonium salt is profoundly dependent on amine structure. These results are consistent with a mechanism in which the selectivity toward macrocyclization versus linear oligomer or high polymer formation is related to acyl ammonium salt concentration.
Partial crystallisation in liquid polymer electrolytes based on co‐polymers of ethylene oxide/propylene oxide
Authors: Cameron G. Gordon , Ingram Malcolm D. , Qureshi M. Younus , Russell Graham M. , Wood Graeme I. 
Published: April 2003

AbstractSolutions of lithium perchlorate in a low molecular weight ethylene oxide/propylene oxide (EO/PO) co‐polymer were studied by differential scanning calorimetry. The pure co‐polymer was found to crystallise partially, while addition of the salt impaired crystallisation first by slowing crystal growth then by slowing nucleation. At high salt concentrations (∼1·0 molal) no crystallisation occurred. The solvation of Li+‐ions and the introduction of ‘transient crosslinking’ between cations and anions effectively suppresses the separation of the polymer into microregions of EO and PO. The crystallisation phenomena are relevant to the use of these copolymers as ‘model’ polymer electrolyte systems.
Mutual diffusion in aqueous gel solutions
Authors: Gutsalyuk V. M. , Guly I. S. , Mel'nichenko Yu. B. , Klepko V. V. , Vasil'ev G. I. , Avdeev N. N. 
Published: April 2003

AbstractConcentration relations for mutual diffusion coefficients Dm(C) in water of polyelectrolyte gelatin macromolecules at different temperatures were studied by optical interferometry. It is shown that Dm(C) values are in agreement with scaling predictions and are similar to those observed for solutions of neutral macromolecules under θ‐conditions. However, they are greatly influenced by the square‐law term C2, having a correlation to the conventional scaling law Dm ∝︁ C, and the mobility of solution components is influenced by physical gelation processes under certain thermodynamic conditions. It is demonstrated that the temperature relation of the diffusion coefficient at infinite dilution D0(C → 0) for the three gelating samples with various physico‐chemical properties can be described by a universal function.
Elastic moduli of liquid crystalline copolymers
Authors: Jawad S. Abdul 
Published: April 2003

AbstractDynamic tensile and shear moduli measurements have been carried out on highly oriented thermotropic liquid crystalline copolymers formed by random copolymerization of 2‐hydroxy‐6‐naphthoic acid, terephthalic acid and p‐aminophenol. This liquid crystalline copolymer is known as HNATA. Application of the aggregate model of units of structure gives rise to an estimation of the orientation angle θ = 5° and a chain modulus Ec = 230 GPa. The fall in tensile modulus with increasing temperature is related to two factors: a decrease in the intrinsic chain modulus and a reduction in the shear modulus.
Dipole moments of poly(allyl methacrylate) prepared by group transfer polymerization
Authors: Erbil Candan , Çatalgil‐Giz Huceste , Uyanik Nurseli 
Published: April 2003

AbstractDipole moments of poly(allyl methacrylate) prepared by group transfer polymerization and of allyl methacrylate were determined from dielectric constant, refractive index increment and density measurements performed on their dilute benzene and carbon tetrachloride solutions within a temperature range of 25–60°C. Dipole moments ratios and temperature coefficient, d ln〈μ2〉/dT, where 〈μ2〉 is the mean‐square dipole moment of the chain, were calculated. These results are compared with earlier results.
The method of incorporating organofunctional silane‐based agents into rubber compounds: Effects on the properties of an SBR‐based compound filled with synthetic calcium silicate
Authors: Kadivec Irena , Šušterič Zoran , Strle Marjetka , Kaučič Venčeslav 
Published: April 2003

AbstractSynthetic calcium silicate, pretreated with various quantities of organofunctional silane (Si‐69®)‐based coupling agents, has been investigated in a compound based on styrene–butadiene rubber. The properties of the rubber compound with untreated synthetic calcium silicate and those observed after direct addition of an adequate quantity of Si‐69® during the mixing period have been compared.
Unexpected effect of the monomer concentration on the rate of a radical polymerization
Authors: Casinos Ismael 
Published: April 2003

AbstractThe radical polymerization of vinyl monomers is usually initiated by physical and chemical means. After an increasing polymerization rate, Rp, at low monomer concentrations, some reactive systems show an unexpected minimum for Rp at high enough monomer concentrations. The radical polymerization of methyl methacrylate (MMA) initiated by the redox system D‐glucose–ceric ion at varying MMA concentration is discussed. The peculiar behaviour of Rp is explained by the presence of two circumstances: the initiation rate from D‐glucose radicals does not depend on MMA concentration when most of the D‐glucose radicals formed react by adding to monomer, and the radical chains initiated by D‐glucose radicals undergo mutual termination with a portion of the radical chains initiated by monomer radicals. Some information about the nature of the polymer end‐groups is reached from the mechanistic approach.
Use of inverse gas chromatography to assess the compatibility of polyurethane foam with liquids at different temperatures
Authors: Jackson Paul L. , Huglin Malcolm B. 
Published: April 2003

AbstractA crosslinked polyurethane foam has been used as the stationary phase in inverse gas chromatography to measure the solubility parameter (δ2) of the polymer at several temperatures (T) within the range 298–383 K. Values of δ2 = 29.5(MPa)1/2 at 298K and dδ2/dT = −0.06(MPa)1/2 K−1 were yielded. Linear decreases with temperature of the solubility parameters (δ1) of water, ethanol and methanol were obtained by calculation from relevant properties of the liquids. The results were used to assess the conditions for the polyurethane foam to act as a non‐interacting barrier against liquids of different polarities for which the criterion is that |δ1 − δ2| should be large. The findings highlight the need to consider both the nature of the liquid and the temperature regime.
Preparation, characterization and alkali metal ion permeation through cross‐linked poly(styrene‐co‐maleic acid) membranes
Authors: Philip Kalathiparambil C. , Pillai Vadasseril N. Sivasankara 
Published: April 2003

AbstractMembranes were prepared from poly(styrene‐co‐maleic acid) under different conditions and characterized by measuring thickness, swelling, electrical resistance, membrane potential and permselectivity. Permeability coefficients of KCl, NaCl, Na2SO4, NaOH, urea and creatinine were evaluated from dialysis experiments. The charged membranes facilitated the active transport of alkali metal ions under a pH gradient. The energy for this movement comes from the simultaneous counter transport of protons.
Desorption of the surfactant from the particle surface during latex film formation
Authors: Kientz E. , Dobler F. , Holl Y. 
Published: April 2003

AbstractProperties of latex films are very dependent on the distribution of the surfactants in the film. It has been recognized that distribution itself depends on the desorption characteristics of the surfactant from the particle‐water interface during film formation. This article deals with this problem of surfactant desorption in the particular situation of latex film formation. First, FTIR spectroscopic evidence is presented for desorption of hexadecyl pyridinium chloride (HPCI) in poly(2‐ethyl hexyl methacrylate) (P2EHMA) latex films. Some consequences of desorption or non‐desorption of various surfactants on the structure and properties of P2EHMA latex films are then presented. This concerns the crystallization of cationic surfactants, HPCI and hexadecyl trimethylammonium bromide (HTAB), in the films and the mechanical properties of films containing ethoxylated nonyl phenol with 10 ethoxy segments (NP10) or sodium dodecyl sulphate (SDS). In the last part, the determination of the fraction of SDS desorbing from the particle–water interface in a model poly(styrene–butyl acrylate–methacrylic acid) latex coalescing in water is described. Other methods for studying desorption are proposed.
Kinetics of liquid crystallization for lyotropic liquid crystalline polymers
Authors: Lin Jiaping , Wu Herong , Li Shijing 
Published: April 2003

AbstractThe kinetics of liquid crystalline phase transition from the isotropic state to the anisotropic state, which is by analogy termed liquid crystallization, for poly(p‐benzamide)(PBA)/H2SO4 and PBA/Nylon 6/H2SO4 systems was investigated by the depolarized light intensity (DLI) technique and polarized light microscopy (PLM). The experimental data were analysed using the Avrami equation. The n value, according to the Avrami equation, is about 1 for both PBA/H2SO4 and PBA/Nylon 6/H2SO4 systems, which suggests that the liquid crystallization of PBA/H2SO4 and PBA/Nylon 6/H2SO4 systems is a process of instantaneous nucleation with one‐dimensional growth. The introduction of Nylon 6 into PBA/H2SO4 does not have any significant effect on the Avrami exponent n. The results also show that the Avrami exponent n and the half‐time for the liquid crystallization are temperature dependent.
Synthesis of polyvinyl acetate‐graft‐poly‐2‐oxazolines
Authors: Dworak Andrzej , Schulz Rolf C. , Panchev Ivan , Trzebicka Barbara , Velitshkova Rumiana 
Published: April 2003

AbstractPoly(vinyl acetate‐co‐vinyl chloroformate) (1) was synthesized via phosgenation of poly(vinyl acetate‐co‐vinyl alcohol). It was shown that (1) is capable of initiating the polymerization of 2‐phenyl‐2‐oxazoline and 2‐methyl‐2‐oxazoline, when the counter ion is exchanged using potassium iodide. Polyvinyl acetate‐graft‐poly‐2‐phenyl‐2‐oxazoline and polyvinyl acetate‐graft‐poly‐2‐methyl‐2‐oxazoline are obtained in the grafting reaction.
A hydrocarbon‐soluble difunctional orgaolithium anionic initiator. Synthesis of 2,2‐bis[3‐(1‐lithio‐2,3‐dimethylpentyl)‐4‐methoxyphenyl]propane
Authors: Sanderson Ronald D. , Roediger Andrew H. A. , Summers Gabriel J. 
Published: April 2003

AbstractThe reaction of stoichiometric amounts of sec‐butyllithium with 2,2‐bis[3‐(1‐propenyl)‐4‐methoxyphenyl]propane (4) produces a new difunctional organolithium initiator, 2,2‐bis[3‐(1‐lithio‐2,3‐dimethylpentyl)‐4‐methoxyphenyl] propane, which is soluble in hydrocarbon solvent in the absence of any polar additive. Following isolation and purification by gas liquid chromatography, the structures of (4) and the methanolysis product of the difunctional initiator were characterized by 1H NMR, FTIR and mass spectroscopy and elemental analysis. The dilithium initiator is effective for the polymerization of 1,3‐butadiene and allows the preparation of polybutadienes with predictable molecular weights, narrow, monomodal molecular weight distribution and low 1,2‐diene microstructure.
Regular network polyamide and copolyamide films from trimesic acid and aliphatic diamines
Authors: Kiyotsukuri Tsuyoshi , Murata Mitsuya , Sugimoto Mariko , Tsutsumi Naoto 
Published: April 2003

AbstractRegular network polyamide films made from trimesic acid (Y) and aliphatic diamines as well as copolyamide films made from hexamethylene diamine (6) and dodecamethylene diamine (12) with Y were prepared. Prepolymers obtained by melt polycondensation for a short period of time were cast from a DMF solution and successively post‐polymerized at 300°C to form a network. The resultant films were transparent, flexible and insoluble in any solvents. Heat distortion temperature (Th) measured by a penetration mode of thermomechanical analysis rapidly increased with increasing post‐polymerization time, and then levelled out after 0.5–1 h. Th was 238, 231, 232, 216, 207, 187, 176 and 163°C for 4Y, 5Y, 6Y, 7Y, 8Y, 9Y, 10Y and 12Y post‐polymerized for 4h, respectively. Degrees of reaction estimated from the infrared absorbance of ester and methylene groups were 88 and 83% for 6Y and 12Y post‐polymerized for 4h, respectively. Two diffraction peaks appeared in the wide angle X‐ray scattering (WAXS) pattern, suggesting some ordered structure owing to the regular networks. Density increased with increasing post‐polymerization time and was 1.266, 1.236, 1.214, 1.175, 1.162, 1.145, 1.130 and 1.107 g/cm3 for 4Y, 5Y, 6Y, 7Y, 8Y, 9Y, 10Y and 12Y post‐polymerized for 4h, respectively. WAXS patterns of copolymer films of 12/6‐Y suggested the continuous change of network structure with copolymer composition. It was found that comonomer disturbs the formation of ordered network structure, and decreases the packing of networks, thus decreasing density, Th and tensile properties, and increasing dye absorption of copolymer films. From the dye absorption behavior, it was suggested that these regular network films could be utilized as membranes for the separation of molecules by varying the chain length between crosslinked sites.
Effect of some structural features of the polymer support on synthesizing 2,4,6‐tribromophenyl benzyl ether in a triphase catalysis
Authors: Wang Maw‐Ling , Peng Ching‐Zou 
Published: April 2003

AbstractThe substitution reaction of benzyl bromide and 2,4,6‐tribromophenol in an organic solvent/alkaline aqueous solution of KOH by triphase catalysis in which tributylamine was immobilized on a polymer support was investigated. Our main purpose was to evaluate the effect of some structural features of the polymer‐supported pellet on the conversion of the organic‐phase reactant (benzyl bromide). The polymer‐supported pellet was obtained from copolymerization of styrene and chloromethylstyrene monomers. The reaction was identified as occurring both on the surface and within the particles of the polymer support when using a highly polar solvent. The effects of the structural features of the polymer support, which are related to the degree of cross‐linking, ring substitution, lipophilicity of the polymer pellet, the chloride density and the solvents, on the conversion of benzyl bromide were investigated in detail. The experimental results indicate that 2% of cross‐linking with 10% ring substitution of the macroporous polymer support provides a rapid reaction and high conversion of benzyl bromide reactant.
Depolarization current characteristics of cellulose acetate–butyrate polymer films
Authors: Reddy N. Venugopal , Rao V. V. R. Narasimha 
Published: April 2003

AbstractCellulose acetate–butyrate films of thickness 5μm were grown by a solution growth technique. Thermally stimulated depolarization currents (TSDCs) were studied on these films as a function of polarizing field strength and polarizing temperature at a constant heating rate. In the present study, the TSDC spectra consist of a single current maximum, which was found to be independent of polarizing field strength. However, the current maximum shifted to higher temperatures with increasing polarizing temperature. The activation energies, relaxation parameters, charge associated with the current maximum and equivalent frequencies were evaluated. Based on these results, the origin of the TSDC was attributed to space charge polarization with some contribution arising from dipolar orientation.
Azeotropy in terpolymerization of 2‐pyrimidyl acrylamide with different alkyl acrylates and acrylonitrile
Authors: El‐Hamouly S. H. , Azab M. M. 
Published: April 2003

Abstract2‐Pyrimidyl acrylamide monomer (2PA) has been prepared by the reaction of 2‐amino pyrimidine with acrylolyl chloride in the presence of triethylamine as catalyst. Its structure was confirmed by IR and1H NMR spectroscopy. Ternary copolymerizations of 2‐pyrimidyl acrylamide monomer (2PA) with methyl acrylate (MA), methyl methacrylate (MMA), ethyl acrylate (EA), butyl acrylate (BuA) and acrylonitrile (AN) were carried out in THF at 65°C in the presence of a free radical initiator. Experimental terpolymerization data agree well with calculations based on the Alfrey–Goldfinger equation. The determination of unitary, binary and ternary azeotropies of the various systems studied were easily handled by a computer. The ternary azeotropic compositions for 2PA–MA–AN and 2PA–MMA–AN were 32.20:17.5:50.30 and 13.54:52.64:33.82mol%, respectively. Pseudo‐azeotropic regions were identified where the deviation between feed and polymer composition is very small.
Sorption studies in a polyurethane–β‐cyclodextrin blend
Authors: Sreenivasan K. 
Published: April 2003

AbstractThe sorption of toluene, butanol, methanol and n‐hexane in polyurethane and a polyurethane–β‐cyclodextrin blend has been studied. The time to reach equilibrium absorption was several times less in the blend in spite of nearly identical diffusion coefficients and % equilibrium absorptions of the diffusants in both materials. The study indicates that rapidity in polymeric membrane mediated separation can be attained by blending β‐cyclodextrin.
Encapsulation of benzil in the cavities of crosslinked styrene‐based copolymers and its conversion to benzilic acid
Authors: Kuriakose Sunny , Pillai V. N. Rajasekharan 
Published: April 2003

AbstractCrosslinking copolymerization of styrene with divinylbenzene, butanediol dimethacrylate and ethyleneglycol dimethacrylate in the presence of benzil in the dissolved state results in benzil‐encapsulated crosslinked polymers. Resins with various crosslink densities were prepared by adjusting the monomer/crosslinker ratio. The benzil entrapped in the cavities was subjected to benzil‐benzilic acid rearrangement. The precursor resins and the rearrangement products were characterized by IR and 13C NMR spectroscopy. The surface properties of polystyrene and benzil‐encapsulated polystyrene were compared by scanning electron micrography.
Synthesis and characterization of optically active 2,4‐disubstituted‐2‐oxazolines and their polymerization
Authors: Guo Xin Qui , Schulz Rolf C. 
Published: April 2003

AbstractFour different optically active 2,4‐disubstituted‐2‐oxazolines were synthesized and characterized. Cationic polymerization of these oxazolines were studied. Three of the oxazolines could be polymerized using methyl trifluoromethanesulfonate as initiator. S‐(–)‐2‐Phenyl‐4‐isopropyl‐2‐oxazoline could not be polymerized under the conditions used.
On the low frequency dielectric behavior of carboxymethyl cellulose and its sodium salt
Authors: Moteleb M. M. Abdel 
Published: April 2003

AbstractA dielectric dispersion and frequency loss peak within the low frequency range 0.05–1 kc/s and at temperatures of 283–333 K was observed in the case of the sodium salt of carboxymethyl cellulose and absent in the case of its acid form. The critical frequency of the dielectric absorption was independent of molecular weight and of the presence of low moisture content. The results obtained show that the variation with temperature of the dielectric constant is exponential at low frequency only in the case of the sodium salt of carboxymethyl cellulose. The significance of the results is discussed.
Optical activity measurements in solids 7. Polylactides and poly(β‐hydroxybutyrates)
Authors: Bartus Jan , Weng Dexi , Vogl Otto 
Published: April 2003

AbstractThe optical activities of poly‐(R)‐lactide, poly‐(S)‐lactide, poly(β‐hydroxybutyrate) and two β‐hydroxyvalerate copolymers were measured in solution, as solid powders in suspension, and where possible, as films. Poly‐(+)‐3‐methyl‐1‐pentene was also reinvestigated. In some cases the specific rotation values of powder samples showed significant differences from the values of the solution measurements. The discrepancies of the data observed seem to reflect the local environment of the polymer chains in supermolecular assemblies and consequently the solid state structure(morphology)of the polymers.The circular dichroism (CD) spectra of the polymers were also measured in solution and in the form of their films. For comparison, the CD spectra of the naturally occurring protein casein and of the synthetic polypeptide poly‐(L)‐proline were also measured.
Use of inverse gas chromatography to quantify interactions in amine cured epoxy resins
Authors: Jackson Paul L. , Huglin Malcolm B. , Cervenka Antonin 
Published: April 2003

AbstractFlory–Huggins interaction parameters, λ, were determined for a series of probes in an amine cured epoxy resin matrix (433–493 K) and its precursors (324–363 K) by inverse gas chromatography (IGC). Hildebrand–Scatchard theory was combined with Flory–Huggins theory in order to estimate infinte dilution solubility parameters (δ2) for the matrix and its precursors at 298 K. It was shown that the value of the solubility parameter for the cured resin matrix lies between those of its precursors. Compared to the majority of published work, an unusual aspect of this application of IGC is that solubility parameters have been determined when the stationery phases are (i) small molecules and (ii) a highly crosslinked polymer. Moreover, all possible attempts have been made to ensure equilibrium conditions between probe and stationary phase, and compensation for asymmetry of peak profile has been applied in determining δ2. The solubility parameters estimated by IGC are in good agreement with those calculated by other methods.