bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polyelectrolyte solutions. Electrical conductivity and counterion condensation
Authors: Ricos Hernán E. , Barraza Raúl G. , Gamboa Irma C. 
Published: April 2007

AbstractWe have analyzed the electrical conductivity of a linear high charge density polyelectrolyte aqueous solution, finding that the counterion association order follows the same pattern as that described for a cyclic monomeric polyelectrolyte, i.e. NO > Br− > Cl− > F−. However, these counterions interact in a very different manner with this polyion, making Eisenberg's relationship inapplicable in this system. Consequently, an alternative method is proposed for treating data.
Synthesis, characterization and kinetics of terpolymerization of acrylonitrile, N‐vinyl pyrrolidone and styrene
Authors: Kumar Paritosh , Narayan D. , Srivastava A. K. 
Published: April 2007

AbstractSynthesis of a series of novel terpolymers, consisting of two electron‐donating monomers, viz. N‐vinyl pyrrolidone (N‐VP) (heterocyclic polar monomer) and styrene (Sty) (non‐polar monomer), with one electron‐accepting polar monomer, i.e. acrylonitrile (AN), using α,α'‐azobisisobutyronitrile as radical initiator and benzene as diluent at 60°C, has been extensively surveyed. Besides the synthesis, an attempt has been made to study the kinetics and various properties of the terpolymers, such as softening temperature and chemical resistance. The system follows non‐ideal kinetics and the kinetic equation for the present system can be written as
equation image
This non‐ideality can be explained on the basis of significant initiator‐dependent termination through primary radicals and degradative chain transfer to acrylonitrile monomer. The overall energy of activation is 72.4 kJ mol−1 and kp2/kt is 0.26 × 10−3 litre mol−1 s−1.The effects of various additives such as imidazolium‐p‐chlorophenacylide (ICPY) and ZnCl2 were also studied. ICPY functions as a chain transfer agent (Ctr = 0.43 × 10−4), whereas ZnCl2 accelerates the rate of reaction. IR spectroscopy was used to confirm the structure of the terpolymers.
Studies on kinetics of bulk polymerization of divinyl ester by radical‐initiated thermal and photo‐polymerization
Authors: Chandra R. , Soni R. K. 
Published: April 2007

AbstractDi(2‐hydroxy propane methacrylate) ester of adipic acid (DAP) was prepared by reacting adipic acid with glycidyl methacrylate using triphenyl phosphine as catalyst. The kinetics of bulk polymerization of the prepared compound using benzoyl peroxide as initiator were determined using isothermal differential scanning calorimetry (DSC). The kinetic order of the reaction (order exponent n and autocatalytic exponent m) and apparent reaction rate constant (k) were determined. The kinetics of radical‐initiated photo‐polymerization of DAP were also studied by differential photocalorimetry (DPC), using benzophenone as initiator. The rate of reaction was found to be much higher in radical‐initiated photo‐polymerization than in radical‐initiated thermal polymerization.
Functionality distribution and crosslink density of hydroxyl‐terminated polybutadiene
Authors: Ninan K. N. , Balagangadharan V. P. , Ambikadevi K. , Catherine K. B. 
Published: April 2007

AbstractA novel approach is proposed for estimating the average molecular weight between crosslinks (M̄c) from the functionality distribution of hydroxyl‐terminated polybutadiene (HTPB). The functionality distribution of four free‐radically polymerised HTPB prepolymers of varying hydroxyl content and molecular weight was determined by a combination of preparative and analytical gel permeation chromatography. The gumstock properties of the samples cured with stoichiometric amounts of toluene diisocyanate were not correlatable with the relative amounts of difunctional chain extender and multifunctional crosslinker present, unlike the case of HTPB with similar hydroxyl content and molecular weight. However, the mechanical properties and sol content could be correlated with the average molecular weight between crosslink sites, M̄c, of the cured polymer. The M̄c values derived by our method compare well with those of classical methods, and the observed differences are attributed to segmental entanglement. These M̄c values give consistently good correlation with all the gumstock properties, confirming the validity of our approach and the soundness of the techniques developed for the determination of the functionality distribution of HTPB.
Template polymerization of chromium acrylate
Authors: Chaturvedi Bharti , Srivastava A. K. 
Published: April 2007

AbstractThe template polymerization of chromium acrylate (CrA3) with poly‐(vinyl acetate) (PVAc, M̄v = 56 265) at 90 ±0.1°C for 2 h in dimethylformamide has been studied dilatometrically to examine the effects of concentration and average molecular weight of template, and of monomer concentration upon the kinetics and mechanism of template polymerization. The viscometric measurements showed that the complexation between poly‐CrA3 and PVAc was at a maximum when the template/polymer ratio was 1:1, and the time required for complete complexation was 8 min. The value of the coefficient of interaction (KAB) between the two polymers was high for DMSO, medium for DMF and low for dioxane, and is a direct function of the polarity of the solvent. The KAB values indicate that an interaction, which consists of van der Waals forces and hydrogen bonding, exists between the polymers. The overall activation energy was 72.1 and 57.3 kJ mol−1 in the absence and presence of PVAc, respectively.
Structure in mesogenic diol‐containing polyesters
Authors: Fischer Hartmut , Karasz Frank E. , Macknight William J. 
Published: April 2007

AbstractCopolyesters synthesized from two mesogenic monomers have been investigated. The monomers are 4,4′‐bis(6‐hydroxyhexoxy)biphenyl (BHHBP) and the p‐diester made from terephthaloyl dichloride and p‐hydroxybenzoic acid. The incorporation of a very rigid, second mesogen increases the ability of BHHBP to form tilted mesophases. An untilted smectic A phase is formed initially, but the final, stable phase is a highly ordered, tilted smectic phase. Similar behavior is observed when BHHBP is combined with a mixture of the diacids of the crown ether dibenzo‐18‐crown‐6. A copolymer of this type also forms a smectic A phase. For both types of copolymers, there is good agreement between the measured and calculated values for the layer distances.
Synthesis of amphiphilic polystyrene–ionene diblock copolymers with controlled block lengths
Authors: Schipper Eugène T. W. M. , van Hest Jan C. M. , Roelofs Alexander H. C. , Piet Pieter , German Anton L. 
Published: April 2007

AbstractAmphiphilic polystyrene‐ionene diblock copolymers with blocks of controlled molecular weights were synthesized by a new method. The preparation starts with the anionic polymerization of styrene with 3‐(dimethylamino)propyl‐lithium as initiator, yielding tertiary amino end‐functionalized polystyrenes of molecular weights that can be varied over a wide range from 1 to 100kg/mol, and a relatively low polydispersity (M̄w/M̄n = 1.1–1.4). The crucial step in this method is the stepwise coupling of the reactive end‐group of the polystyrene with bromo‐ and tertiary‐amino‐terminated monodisperse oligomeric 2,4‐ionenes. The amphiphilic polymers with well‐defined block lengths were characterized by thin‐layer chromatography, end‐group titration and elemental analysis. Amphiphilic block copolymers with a monodisperse ionene block consisting of up to 10 quaternary ammonium groups could be derived.
Kinetic investigation of the radical polymerization of N‐acryloylpiperidine in solution
Authors: Ebraheem Kais A. K. , Al‐Issa Mahmoud A. , Mohammed Nedhal Y. 
Published: April 2007

AbstractThe kinetics of free radical polymerizations of N‐acryloylpiperidine (NAPi) were studied in benzene (Bz) using 2,2′‐azobisisobutyronitrile (AIBN) as initiator. The activation energy was determined to be 111.7 kJ mol−1. The overall rate of polymerization of the NAPi‐AIBN‐Bz system at 60°C was investigated as a function of monomer and initiator concentrations. Deviation from normal kinetics was observed with an order of 1.48 with respect to the monomer. The observed dependence of the rate constants kp/k on monomer concentration could not be explained by the diffusion theory or the theory of electron donor‐acceptor (EDA) complexes. The observed data have, however, been satisfactorily interpreted by the ‘hot’ radical theory.
Thermal and mechanical properties of thermoplastic polyurethane elastomers from different polymerization methods
Authors: Ahn Tae Oan , Choi Ii Seok , Jeong Han Mo , Cho Kilwon 
Published: April 2007

AbstractThermoplastic polyurethane elastomers (TPUs) based on 4,4′‐methylene‐diphenyl diisocyanate, poly(tetramethylene glycol), diamine‐terminated aliphatic nylon oligomer, and 1,4‐butanediol were synthesized by two different polymerization methods, i.e. one shot and prepolymer methods. The effects of the polymerization method on the thermal and mechanical properties of the TPUs have been studied. A broader distribution of hard segment lengths in TPUs prepared by the one shot method was observed from thermal and tensile property measurements, compared with those prepared by the prepolymer method. TPUs by the one shot method showed a higher Tm of the hard segments and better tensile properties when soft‐hard segment interaction was relatively small. However, inferior tensile properties were observed when the soft‐hard segment interaction was high; typically when nylon oligomer was used as a soft segment.
Association between polyether–polyamine block‐copolymers and low molecular weight polyacids in solution
Authors: Toncheva Veska , Velichkova Roumiana , Trossaert Geert , Goethals Eric J. 
Published: April 2007

AbstractAn ABA block‐copolymer in which A is a poly(N‐tert‐butylimino‐ethylene) segment and B a poly(oxytetramethylene) segment has been prepared. The salt form of this polymer, obtained with low molecular weight polycarboxylic acids such as citric acid or benzene‐1,3,5‐tricarboxylic acid, was found to form ionic networks in organic solvents of low or medium polarity, when the concentration of the polymeric salt exceeded a critical concentration, between 2 and 4wt%. The viscosities of the polymeric salt solutions were strongly pseudoplastic, showing a yield point and thixotropic behaviour.
Durable glass–epoxy composites cured at low temperatures—Effects of thermal cycling, UV irradiation and wet environment
Authors: Rinaldi Gilberto , Maura Giancarlo 
Published: April 2007

AbstractGlass‐fibre‐epoxy composites cured with oligomeric polyaminophenolic agents have shown good dimensional stability during thermal cycling at temperatures over 100°C, even if their curing is carried out at room temperature. It was therefore believed important to evaluate their behaviour in different environmental conditions. Their good mechanical characteristics are maintained after saturation with water, UV irradiation, and thermal cycling between 0 and 110°C. From the following tests the environmental resistance is clearly higher than that of composites cured with other aminic agents.
Curing theory of the Aai–Bbj type polycondensation. (I) intramolecular cyclization and gelation equations
Authors: Zheng Fu‐An , Liu Feng‐Qi , Tang Xin‐Yi 
Published: April 2007

AbstractThis paper investigates in detail the ring‐chain competition in Aai–Bbj type polycondensations by use of a molecular model of tree branching and the basic principles of probability. The intramolecular cyclization equations and the critical gelation condition containing both intermolecular and intramolecular reaction parameters have been obtained.
Curing theory of the Aai–Bbj type polycondensation. (II) sol‐gel distribution
Authors: Zheng Fu‐An , Hu Yu‐Xin , Min Yong‐Gang , Tang Xin‐Yi 
Published: April 2007

AbstractAn alternative way is proposed to approach the sol‐gel distribution of Aai–Bbj type polycondensation by taking into consideration intramolecular reaction. The equations deduced basically from the definition of the sol fraction and the chemical equilibrium of reactants in this paper can be reduced to those of Tang Au‐chin's and Miller's expressions. Comparing experimental with theoretical values, we found that the results of this paper are closer to the real cases than those of other authors.
Stability and compatibility in blends of silicone and vinylacrylic polymer emulsions
Authors: Richard J. , Mignaud C. , Sartre A. 
Published: April 2007

AbstractSpecial, unexpected properties may arise from blending of polymer emulsions, depending on the miscibility and stability of the resulting dispersions on the one hand, and the morphology of the films obtained upon drying on the other hand. In the field of water‐repellent paints, blends of silicone and vinylacrylic copolymer emulsions have been previously shown to be a tricky means to associate binding ability and water permeability properties in the same material. It is currently assumed that the resulting morphology and physical properties of films obtained from these blends upon drying is partially controlled by the compatibility of the two kinds of polymers. In the present paper, the crucial problem of stability and compatibility in blends of silicone and vinylacrylic copolymer emulsions is investigated; more particularly, the effect of pH of the vinylacrylic copolymer latex, as well as the influence of the stabilizing system of both emulsions, on the stability of emulsion blends is qualitatively described. As regards the morphology of the films, the strong incompatibility of the two polymers is shown, which results in large macroscopic heterogeneities in the dried composite films. Furthermore, semi‐quantitative angle‐resolved ESCA measurements have evidenced a pronounced diffusion of the silicone species towards the surface of the samples. Investigations into different ways to increase compatibility of the two phases is presented. It is shown that phase separation at the macroscopic scale can be controlled either by lowering the interfacial tension between the two phases by grafting silane compatibilizers on to the latex particles, or by decreasing the molecular mobility of the silicone phase by cross‐linking. Diffusion of the silicone chains towards the surface of the composite films can only be significantly restricted by cross‐linking of this species.
Synthesis and characterisation of carboxylic acid and diphenylphosphine derivatives in the 1,3‐diyne series: Spectral properties of polydiacetylene carboxylates
Authors: Agh‐Atabay N. M. , Lindsell W. Edward , Preston Peter N. , Tomb Peter J. 
Published: April 2007

AbstractSymmetrically substituted 1,3‐diynes containing hydroxyalkyl (1a‐d), bromoalkyl (1e‐h) (diphenylphosphinyl) (1i‐k) and carboxyalkyl (2a‐d) substituents have been prepared and characterised; the phosphine derivative (1k) has been converted with alkyl iodides (RI; R = Me, Et) into bis(phosphonium) salts (1l and m). During preparation of the diynedioic acid. (2a), the non‐centrosymmetrical diyne, HO2CCH2CC—CC(CH2)2OH (3), was also isolated. 60Co γ‐Irradiation of diacetylene monomers (2a–d) and 10,12‐tricosadiyn‐1‐oic acid gave the corresponding polydiacetylene derivatives (4a–d and 5), respectively. Rubidium salts of (4c) and (4d), a barium salt of (4c), and a potassium salt of (5) were prepared and isolated; soluble potassium salts of the carboxylic acid polymers (4) were generated in aqueous solution. The effects of changes in pH on the UV/visible absorption spectra of aqueous solutions of selected carboxylic acid polydiacetylenes have been recorded, and are discussed.
Reactivity ratios for new copolymerizations relevant to thermosetting resins
Authors: Mao Runsheng , Huglin Malcolm B. , Davis Thomas P. , Overend Andrew S. 
Published: April 2007

AbstractFree radical copolymerizations of four new systems, namely (1) methyl methacrylate (MMA) with β‐acryloxypropionic acid (AOPA); (2) MMA with p‐styrene sulphonyl chloride (SSC); (3) 2‐[(phenylamino) carbonyl] oxyethyl methacrylate (PCOMA) with 2‐phenoxyethyl methacrylate (PEMA); and (4) PCOMA with 1‐methyl‐2‐phenoxyethyl methacrylate (MPEMA), have been carried out at 60°C for systems 1 and 2 and at 70°C for systems 3 and 4. The copolymer compositions were analysed by acid‐base titration for system 1 and by FTIR for systems 2–4. The monomer reactivity ratios as well as the 95% individual confidence intervals and 95% joint confidence intervals were calculated from the Kelen‐Tüdős method, the Extended Kelen‐Tüdőos method, and from a new iterative linear method by Mao and Huglin. The results show that all these copolymerizations are strictly linear systems describable by the Mayo‐Lewis equation based on the terminal model and that accurate reactivity ratio data can be obtained. The Q‐e values of the monomers AOPA and SSC have been estimated. Some physical properties of AOPA, PEMA and MPEMA are also presented for the first time.
Nucleophilic reactivity of aniline derivatives towards the nitroso group
Authors: da Silva Gabriel , Kennedy Eric M. , Dlugogorski Bogdan Z. 
Published: April 2007

AbstractThis study investigates the reactivity of the electrophilic nitroso group towards nucleophilic aniline derivatives from various nitrosating agents. A relationship between the rate of nitrosation and Edwards' nucleophilic parameter (En) is disclosed, indicative of a transition state that is mostly product‐like in nature with respect to cleavage of the nitroso bond in the nitrosating agent. A similar relationship based on the work of Marcus provides a considerably better explanation of the data. Through application of the Marcus equation, the free energy change of reaction is calculated for the nitrosation reactions studied, which in turn is applied to develop an equation linking the free energy of formation of a nitrosamine and its corresponding protonated amine. This equation accounts for the often‐observed Brønsted relationships in nitrosation reactions. The intrinsic barrier to reaction is estimated to be 10 kJ mol−1, indicating that the main impedance to nitrosation arises from the unfavourable reaction thermodynamics. However, for the nitrosation of aniline derivatives substituted with π‐electron withdrawing groups, an unbalancing of the transition state results in an increased intrinsic barrier, of the order of 19 kJ mol−1. For electronic‐effect aniline derivatives, a More O'Ferrall–Jencks diagram shows the nitrosation transition state to be synchronously well balanced between reactants and products. This diagram also confirms that the reaction follows a concerted mechanism. The nitrosation of resonance‐stabilised aniline derivatives is somewhat less synchronous, however, due to delocalisation of the lone electron pair on the amino group, induced by π electron withdrawing substituents. Transition states were located according to the theory of harmonic parabolic wells. The results of these calculations agreed with transition state locations predicted using linear free energy relationship techniques. A method is developed which approximates free energy profiles by treating the product and reactant free energy wells as harmonic parabola, while the free energy profile around the transition state is taken as the parabolic barrier to the product and reactant energy wells. Applying this technique, free energy profiles for electronic‐effect and resonance‐stabilised aniline nitrosation are predicted, utilising measured kinetic values and predicted thermodynamic properties. We couple the simulated free energy profiles with their corresponding More O'Ferrall–Jencks diagrams in order to elucidate the three‐dimensional reaction path traversed between reactants and products, in terms of both structure and energy. We also demonstrate that the nitrosonium ion behaves as a soft acid, and should therefore undergo covalent frontier‐orbital controlled bonding. Copyright © 2007 John Wiley & Sons, Ltd.
Work disability associated with cancer survivorship and other chronic conditions
Authors: Short Pamela Farley , Vasey Joseph J. , BeLue Rhonda 
Published: April 2007

AbstractThe long‐term effects of cancer and its treatment on employment and productivity are a major concern for the 40% of cancer survivors in the U.S. who are working age. This study's objectives were (1) to quantify the increase in work disability attributable to cancer in a cohort of adult survivors who were an average of 46 months post‐diagnosis and (2) to compare disability rates in cancer survivors to individuals with other chronic conditions. Data from the Penn State Cancer Survivor Study (PSCSS) and the Health and Retirement Study (HRS) were compared. The PSCSS sample included 647 survivors age 55–65, diagnosed at four medical centers in Pennsylvania and Maryland. There were 5988 similarly aged subjects without cancer in the HRS. Adjusted odds ratios for work disability were estimated for cancer survivorship, heart disease, stroke, diabetes, lung disease, and arthritis/rheumatism with multivariate logistic regression. Even for cancer‐free survivors, the adjusted disability rate was significantly higher in comparison to adults with no chronic conditions (female OR = 1.94; male OR = 1.89). There were few significant differences between disability rates for cancer and other conditions. The elevated disability rate is another argument for viewing cancer survivorship as a chronic condition potentially requiring a broad range of psychosocial services. Copyright © 2007 John Wiley & Sons, Ltd.
The impact of physical and psychosocial factors on work characteristics after cancer
Authors: Steiner John F. , Cavender Tia A. , Nowels Carolyn T. , Beaty Brenda L. , Bradley Cathy J. , Fairclough Diane L. , Main Deborah S. 
Published: April 2007

AbstractMost previously employed cancer survivors continue to work after treatment, but the impact of cancer symptoms or psychosocial concerns on their work has seldom been assessed. We conducted a community‐based survey of cancer survivors from the Colorado Central Cancer Registry to assess the changes in their work and the demographic, clinical, and psychosocial characteristics associated with work changes over the 2 years following diagnosis. Of 100 survivors, 92 returned to work, but 57% of those reduced their work by more than 4 h/week, and 56% noted a change in some aspect of their occupational role. Physical symptoms, particularly lack of energy or nausea/vomiting, and psychological symptoms, particularly feeling bored or useless or feeling depressed, were significantly associated with a reduction in work hours or a change in occupational role. Since changes in work are common and are associated with both physical and psychosocial symptoms, strategies are needed to reduce symptom burden and barriers to work and to improve work capacity for working‐age cancer survivors. Copyright © 2007 John Wiley & Sons, Ltd.