bluuebunny/crossref_metadata_2025 huggingface dataset:
Non‐empirical calculations of NMR indirect carbon–carbon coupling constants. Part 4: Bicycloalkanes
Authors: Krivdin Leonid B.
Published: May 2003

A systematic study of the one‐bond and long‐range J(C,C), J(C,H) and J(H,H) in the series of nine bicycloalkanes was performed at the SOPPA level with special emphasis on the coupling transmission mechanisms at bridgeheads. Many unknown couplings were predicted with high reliability. Further refinement of SOPPA computational scheme adjusted for better performance was carried out using bicyclo[1.1.1]pentane as a benchmark to investigate the influence of geometry, basis set and electronic correlation. The calculations performed demonstrated that classical ab initio SOPPA applied with the locally dense Dunning's sets augmented with inner core s‐functions used for coupled carbons and Sauer's sets augmented with tight s‐functions used for coupled hydrogens performs perfectly well in reproducing experimental values of different types of coupling constants (the estimated reliability is ca 1–2 Hz) in relatively large organic molecules of up to 11 carbon atoms. Additive coupling increments were derived for J(C,C), J(C,H) and J(H,H) based on the calculated values of coupling constants within SOPPA in the model bicycloalkanes, in reasonably good agreement with the known values obtained earlier on pure empirical grounds. Most of the bridgehead couplings in all but one bicycloalkane appeared to be essentially additive within ca 2–3 Hz while bicyclo[1.1.1]pentane demonstrated dramatic non‐additivity of −14.5 Hz for J(C,C), +16.6 Hz for J(H,H) and −5.5 Hz for J(C,H), in line with previous findings. Non‐additivity effects in the latter compound established at the SOPPA level should be attributed to the through‐space non‐bonded interactions at bridgeheads due to the essential overlapping of the bridgehead rear lobes which provides an additional and effective non‐bonding coupling path for the bridgehead carbons and their protons in the bicyclopentane framework. Copyright © 2003 John Wiley & Sons, Ltd.
A new scheme for imposing a minimum length scale in topology optimization
Authors: Poulsen Thomas A.
Published: May 2003

A new scheme for imposing a minimum length scale in topology optimization is presented. It guarantees the existence of an optimal design for a large class of topology optimization problems of practical interest. It is formulated as one constraint that is computationally cheap and for which sensitivities are also cheap to compute. The constraint value is ideally zero, but it can be relaxed to a positive value. The effect of the method is illustrated in topology optimization for minimum compliance and design of compliant mechanisms. Notably, the method produces compliant mechanisms with distributed flexibility, something that has previously been difficult to obtain using topology optimization for the design of compliant mechanisms. The term ‘MOLE method’ is suggested for the method. Copyright © 2003 John Wiley & Sons, Ltd.
Convergence of the fixed point theorem with random parameters
Authors: Poirion F.
Published: May 2003

Solving stochastic non‐linear dynamical problems represents a formidable task which, in many cases, can be achieved solely through numerical simulation techniques. This is true for high dimensional as well as low dimensional problems. One method to deal with the non‐linearity is to use the fixed point theorem which gives the convergence conditions of the iterative scheme towards the equilibrium point of the equation. In this paper we look at the particular case where the equilibrium equation depends on a random variable. This case arises for instance in the study of coupled non‐linear dynamical systems when structural uncertainties are introduced in the dynamical systems. We give almost sure and L p convergence conditions for the simulation iterative scheme. Copyright © 2003 John Wiley & Sons, Ltd.
An indirect elastodynamic boundary element method with analytic bases
Authors: Shen Shih‐yu
Published: May 2003

An indirect time‐domain boundary element method (BEM) is presented here for the treatment of 2D elastodynamic problems. The approximated solution in this method is formulated as a linear combination of a set of particular solutions, which are called bases. The displacement and stress fields of a basis are analytically derived by means of solving Lame's displacement potentials. A semi‐collocation method is proposed to be the time‐stepping algorithm. This method is equivalent to a displacement discontinuity method with piecewise linear discontinuities in both space and time. The resulting time‐stepping scheme is explicit. The BEM is implemented to solve three numerical examples, Lamb's problem, half‐plane with a buried crack and Selberg's problem. Though Lamb's problem is considered a difficult problem for numerical methods, the current numerical results for the surface displacements show accurately the characteristics of the Rayleigh wave. This method is efficient and accurate. Copyright © 2003 John Wiley & Sons, Ltd.
Worst‐case design in head impact crashworthiness optimization
Authors: Craig K. J. , Stander Nielen , Balasubramanyam Suri
Published: May 2003

This paper describes the solution of a worst‐case design optimization problem of head impact in automotive design. The worst‐case design process uses an optimization algorithm that can locate saddlepoints: points in the design space where the objective function is maximized with respect to some design variables (worst case) while it is minimized with respect to other design variables simultaneously. The worst‐case design methodology is first tested using two analytic functions. Both functions contain saddlepoints, while the second one also has a random analytic noise component and an integer variable. Thereafter, the methodology is applied to the worst‐case design of a crashworthiness head impact problem. The head impact problem contains both numerical noise and an integer variable. For the first analytical case, the effect of separability of the maximization and minimization variables is investigated by rotating the design variable axes. For the second analytical case, analytical noise in the form of a modified Griewank function and an integer variable is added. For the head impact problem, cases are presented where maximization and minimization are first performed separately, and then in a combined fashion to locate the saddle point. The case studies illustrate the power of this approach in the automotive occupant safety design field. Copyright © 2003 John Wiley & Sons, Ltd.
A comparison of modelling methods for polydispersed wet‐steam flow
Authors: White A. J.
Published: May 2003

Spontaneous nucleation of water droplets in moist air or steam may result in droplet spectra which are complex in shape and which span a broad range of sizes. This is particularly true if the flow is transonic or supersonic with shock waves present, or if an already droplet‐laden flow re‐expands to give secondary or tertiary nucleations. Computation of such flows requires careful modelling of the size distributions if two‐phase behaviour is to be accurately predicted. In this paper, three methods are presented for treating size distributions and growth of the liquid phase in condensing steam: a mixed Eulerian–Lagrangian method, a fully Eulerian method, and a method based on moments of the droplet spectra. These are compared by computing condensing flow within a one‐dimensional supersonic nozzle under conditions that yield very different types of size spectra. Copyright © 2003 John Wiley & Sons, Ltd.
Symmetric‐Galerkin BEM simulation of fracture with frictional contact
Authors: Phan A.‐V. , Napier J. A. L. , Gray L. J. , Kaplan T.
Published: May 2003

A symmetric‐Galerkin boundary element framework for fracture analysis with frictional contact (crack friction) on the crack surfaces is presented. The algorithm employs a continuous interpolation on the crack surface (utilizing quadratic boundary elements) and enables the determination of two important quantities for the problem, namely the local normal tractions and sliding displacements on the crack surfaces. An effective iterative scheme for solving this non‐linear boundary value problem is proposed. The results of test examples are compared with available analytical solutions or with those obtained from the displacement discontinuity method (DDM) using linear elements and internal collocation. The results demonstrate that the method works well for difficult kinked/junction crack problems. Copyright © 2003 John Wiley & Sons, Ltd.
Autonomous decentralized finite element method and its applications
Authors: Honma Toshio , Tosaka Nobuyoshi
Published: May 2003

In this paper, a new solution procedure using the finite element technique in order to solve problems of structure analysis is proposed. This procedure is called the autonomous decentralized finite element method because it is based on the characteristic autonomy and decentralization in life or biological systems (life‐like approach). The fundamental approach is developed according to an idea of cellular automata manipulation by the new neighbourhood model. The finite element method with an algorithm of the relaxation method is adopted as the solution procedure in this approach. The proposed procedure demonstrates that it is a powerful means of numerical analysis for many kinds of structural problems that are structural morphogenesis, structural optimization and structural inverse problems. Our procedure is applied to numerical analysis of three simple plane models: (1) The structural shape analysis problem for the prescribed displacement mode of a truss structure, (2) An adaptive structure remodelling problem on an elastic continuum, (3) An identification problem of thermal conductivity on a continuum. The effectiveness and validity of our idea are shown from their numerical results. Copyright © 2003 John Wiley & Sons, Ltd.
Mixed finite element method for saturated poroelastoplastic media at large strains
Authors: Li Xikui , Liu Zejia , Lewis R. W. , Suzuki Kiichi
Published: May 2003

A mixed finite element for hydro‐dynamic analysis in saturated porous media in the frame of the Biot theory is proposed. Displacements, effective stresses, strains for the solid phase and pressure, pressure gradients, and Darcy velocities for the fluid phase are interpolated as independent variables. The weak form of the governing equations of coupled hydro‐dynamic problems in saturated porous media within the element are given on the basis of the Hu–Washizu three‐field variational principle. In light of the stabilized one point quadrature super‐convergent element developed in solid continuum, the interpolation approximation modes for the primary unknowns and their spatial derivatives of the solid and the fluid phases within the element are assumed independently. The proposed mixed finite element formulation is derived. The non‐linear version of the element formulation is further derived with particular consideration of pressure‐dependent non‐associated plasticity. The return mapping algorithm for the integration of the rate constitutive equation, the consistent elastoplastic tangent modulus matrix and the element tangent stiffness matrix are developed. For geometrical non‐linearity, the co‐rotational formulation approach is used. Numerical results demonstrate the capability and the performance of the proposed element in modelling progressive failure characterized by strain localization due to strain softening in poroelastoplastic media subjected to dynamic loading at large strain. Copyright © 2003 John Wiley & Sons, Ltd.
Qualitative determination of false‐positive effects in the acetylcholinesterase assay using thin layer chromatography
Authors: Rhee In K. , van Rijn Richard M. , Verpoorte Robert
Published: May 2003

A method has been developed to determine the false‐positive effects on acetylcholinesterase inhibition in the TLC assay based on Ellman's method. Various aldehydes and amines have been tested in order to determine whether the observed inhibition is due to a true enzyme inhibition or due to the inhibition of the reaction between thiocholine and 5,5′‐dithiobis‐(2‐nitrobenzoic acid). 4‐Dimethylaminobenzaldehyde, 3‐ethoxy‐4‐hydroxybenzaldehyde, diethylamine, triethylamine, triethanolamine and tyramine showed real enzyme inhibition, although their activity was about 103 times lower than that shown by galanthamine. Heptanal, decanal, cinnamaldehyde, anisaldehyde, benzaldehyde, hexylamine and tryptamine appeared to show a non‐specific chemical inhibition. By checking this chemical inhibition on the TLC assay, the true enzyme inhibition could be distinguished from the false‐positive chemical inhibition observed in the toluene extract of Nerine bowdenii in the course of isolation of active compounds. Copyright © 2003 John Wiley & Sons, Ltd.
Determination of diterpenoid triepoxides in Tripterygium wilfordii by micellar electrokinetic capillary chromatography
Authors: Song Xiurong , Yang Gengliang , Zhao Jingxiang , Chen Yi , Sun Hanwen , Zhang Hongyi
Published: May 2003

A micellar electrokinetic capillary chromatographic (MEKC) method has been established for the identification and determination of diterpenoid triepoxides in the Chinese herb Tripterygium wilfordii Hook F. and its preparations. Studies of the influence of boric acid and borax buffer concentration and pH, and of sodium dodecylsulphate (SDS) concentration have been carried out, and the optimum separation for the triepoxides was achieved using 20 mM boric acid and 10 mM borax with 20 mM SDS as the running buffer. MEKC was found to exhibit good accuracy, precision and repeatability. The sensitivity of the assay was sufficient to monitor the three active components in T. wilfordii and its preparations. Copyright © 2003 John Wiley & Sons, Ltd.
Determining acetylcholinesterase inhibitory activity in plant extracts using a fluorimetric flow assay
Authors: Rhee In Kyung , Appels Natalie , Luijendijk Teus , Irth Hubertus , Verpoorte Robert
Published: May 2003

A fluorometric assay for acetylcholinesterase inhibitory activity was developed in a flow system using the fluorogenic substrate 7‐acetoxy‐1‐methyl quinolinium iodide which is hydrolysed to the highly fluorescent 7‐hydroxy‐1‐methyl quinolinium iodide. The detection limit of galanthamine is 0.5 µM, which is about 20 times more sensitive than in the colorimetric flow assay. In the presence of 30% methanol or of 5% acetonitrile, about 70% of the enzyme activity could still be detected. Various plant extracts have been screened using the described system including bulbs of Galanthus nivalis, Eucharis amazonica (E. × grandiflora), Crinum powelli and Nerine bowdenii (all members of the Amaryllidaceae), which showed strong AchE inhibitory activity. Copyright © 2003 John Wiley & Sons, Ltd.
Purification of anthocyanins from species of Banksia and Acacia using high‐voltage paper electrophoresis
Authors: Asenstorfer Robert E. , Morgan Anne L. , Hayasaka Yoji , Sedgley Margaret , Jones Graham P.
Published: May 2003

A new method has been developed for the isolation and rapid identification of anthocyanins from two floricultural crops based on the use of high‐voltage paper electrophoresis with bisulphite buffer. Using this method, anthocyanin pigments were successfully purified as their negatively charged bisulphite‐addition compounds from crude extracts of plant tissue. In conjunction with liquid chromatography–electrospray mass spectrometry, the method enabled the anthocyanins from the flowers of two Banksia species and the leaves of two Acacia species to be identified. The Banksia flowers contained both cyanidin and peonidin‐based pigments, while the Acacia leaves contained cyanidin and delphinidin derivatives. Copyright © 2003 John Wiley & Sons, Ltd.
Identification and quantification of methyl jasmonate in leaf volatiles of Arabidopsis thaliana using solid‐phase microextraction in combination with gas chromatography and mass spectrometry
Authors: Meyer Riaan , Rautenbach George F. , Dubery Ian A.
Published: May 2003

Static headspace sampling with solid‐phase microextraction has been used in combination with GC‐FID and GC‐MS for the specific enrichment, identification and quantification of volatile methyl jasmonate secreted by wounded leaves of Arabidopsis thaliana. The microsample method of analysis was found to be precise, accurate, sensitive and rapid. The detection limit of the procedure is 1.5 ppb (∼1.3 ng) per injection, which is of adequate sensitivity to detect the natural baseline levels of methyl jasmonate (∼10–100 ng/g) present in plant tissues. The method can be applied to most plants, requires a minimum of sample material, and shows the additional advantage that it is suitable for automation and could thus be used for high‐throughput screening. Copyright © 2003 John Wiley & Sons, Ltd.
Determination of manganese (II) in some medicinal plants and their decoctions by a kinetic spectrophotometric method
Authors: Mutaftchiev Konstantin , Tzachev Kamen
Published: May 2003

The catalytic effect of manganese (II) on the oxidation of the azo dye tropaeolin 00 with potassium periodate in the presence of 1,10‐phenanthroline was investigated. The reaction was followed spectrophotometrically by measuring the decrease in the absorbance of the azo dye at 445 nm. Under the optimum analytical conditions, manganese (II) in the range 0.05–2.5 ng/mL could be determined by the fixed‐time method with a detection limit of 0.02 ng/mL. The developed method is highly sensitive, selective and simple, and was applied successfully to analyse decoctions of some medicinal plants for trace amounts of total manganese (II) and free manganese (II) ions without separation. Copyright © 2003 John Wiley & Sons, Ltd.
Electrospray mass spectrometric decomposition of some glucuronic acid‐containing flavonoid diglycosides
Authors: Frański Rafał , Eitner Krystian , Sikorska Maria , Matławska Irena , Stobiecki Maciej
Published: May 2003

Mass spectrometric fragmentation patterns of herbacetin 3‐O‐glucopyranoside‐8‐O‐glucuronopyranoside (1), gossypetin 3‐O‐glucopyranoside‐8‐O‐glucuronopyranoside (2) and takakin 7‐O‐glucopyranoside‐8‐O‐glucuronopyranoside (3) were elucidated from mass spectra obtained with electrospray ionisation. The usefulness of the fragmentation patterns observed in the positive and negative mode for structural elucidation of the studied compounds is discussed. The fragmentation of 3 was substantially different from 1 and 2, especially in the negative mode. In order to explain these differences, theoretical calculations were performed. Copyright © 2003 John Wiley & Sons, Ltd.
‘Are you being converted to partial…?’
Authors: Wales JK
Published: May 2003

A new system of partial booking for outpatients is being introduced in the NHS, which will include hospital diabetic clinics. What is the likely impact on the care of patients? Some believe it will make the service more user friendly; others think it will be a long‐term disaster. What do you think? Let us know. Copyright © 2003 John Wiley & Sons, Ltd.
Subcutaneous insulin without a needle: a pilot evaluation of the J‐Tip® delivery system
Authors: Stephens JW , Butteriss D , Payne N , Barker SGE , Hurel SJ
Published: May 2003

The J‐Tip® device has been approved for the delivery of liquid therapeutic agents into the subcutaneous space. Our aim in this pilot study was to evaluate the J‐Tip® as an alternative method of insulin delivery.

Ten patients with stable type 1 diabetes, treated with a multiple dosing regimen, attended on each of two days. On day one, each self‐administered their morning dose of Actrapid with their usual injection pen, and on day two with the J‐Tip®. Blood samples for plasma glucose and insulin measurements were collected over a four‐hour period. All subjects completed an evaluation questionnaire.

No significant difference was observed in mean plasma glucose or insulin at any of the sampling times using the two different methods of insulin delivery. Only one subject reported soreness, or bruising, at the delivery site.

This pilot study shows that the J‐Tip® needle‐free delivery system is an effective and alternative method to administer subcutaneous insulin. Copyright © 2003 John Wiley & Sons, Ltd.
Implementation of an effective outpatient intensive education programme for patients with type 1 diabetes
Authors: Everett J , Jenkins E , Kerr D , Cavan DA
Published: May 2003

Education for our local clinic population with type 1 diabetes was unsatisfactory with an HbA1c audit revealing suboptimal diabetes control. Clinical practice was changed to offer structured, group education to newly diagnosed and established patients with type 1 diabetes. Since 1999, 58 patients, 28 male, mean age 32 (range 18–65) years, mean duration of diabetes 2 (range 0.6–34) years have completed the programme.

HbA1c (mean±SE) fell from 8.9±0.2% to 8.4±0.2% (p<0.001) at three months, was maintained at six months, 8.6%±0.3 at 12 months and 8.3%±0.5 at 24 months. These results were dependent upon the duration of diabetes and the HbA1c level at entry. Mean diabetes management skills, as measured by the Ipswich Questionnaire, rose from 135 (95% CI 126–138) to 151 (95% CI 147–155) at three months (p<0.0001, paired t test) and this was maintained to 12 months. Food knowledge improved in terms of recognising and counting carbohydrates.

In conclusion, we have demonstrated that an intensive education programme for type 1 diabetes can be implemented, audited and resourced within a clinic population. Copyright © 2003 John Wiley & Sons, Ltd.
Efficacy of triple combination oral hypoglycaemic therapy using rosiglitazone, metformin and sulphonylurea in lowering HbA1c
Authors: Byrne J , Garg S , Vaidya A , Rajbhandari SM , Wallis SC
Published: May 2003

Thiazolidinediones are a new class of oral hypoglycaemic agents, which have been reviewed by the National Institute for Clinical Excellence (NICE) and guidelines published. There is ambiguity in the NICE guidelines regarding the use of the triple combination of sulphonylurea, metformin and thiazolidinedione to treat type 2 diabetes. However, in our retrospective audit we found that triple therapy was used in 52% of patients treated with thiazolidinediones. When we analysed the effect of triple therapy we found that it significantly (p<0.05) reduced HbA1c from 9.6% (±1.5%) to 8.4% (±1.1%). Further prospective studies will be needed to confirm this. Copyright © 2003 John Wiley & Sons, Ltd. Copyright © 2003 John Wiley & Sons, Ltd.
Homopolymers and copolymers of acrylates and methacrylates of homoterpenylmethyl carbinol and α‐campholenol
Authors: Liepins R. , Marvel C. S.
Published: May 2003

Acrylates and methacrylates of homoterpenylmethyl carbinol and α‐campholenol were homopolymerized. Copolymers with each other and acrylonitrile were studied. Terpolymers of the acrylate of homoterpenylmethyl carbinol and the acrylate of α‐campholenol with butadiene and styrene or acrylonitrile were also prepared. The lactone ring in the homopolymer of methacrylate of homoterpenylmethyl carbinol was opened up under basic conditions at room temperature, yielding a water‐soluble polymer. Films of this polymer were cast from a water solution. The acrylate of homoterpenylmethyl carbinol gave a high molecular weight copolymer with acrylonitrile which could be molded into a transparent, extremely tough, film. The terpolymers of the acrylate of homoterpenylmethyl carbinol with butadiene and styrene or acrylonitrile were obtained in high yield and could be molded into strong, rubbery films. Several polymers were epoxidized and cured with p‐phenylenediamine.
Polymerization of methyl 12‐acryloxystearate, N,N‐dimethyl 12‐acryloxystearamide, and methyl 14‐acryloxyeicosanoate
Authors: Sowa J. R. , Marvel C. S.
Published: May 2003

Several homopolymers and copolymers of the title compounds have been prepared by radical initiation with potassium persulfate or diethyl azobisisobutyrate. The copolymers exhibit a combination of the properties of the homopolymers of the monomers. The homopolymers are adhesive, very slightly elastic, and show cold flow. Several of the copolymers show possible promise for use as adhesives.
Colored electrically conducting polymers from furan, pyrrole, and thiophene
Authors: Armour M. , Davies A. G. , Upadhyay J. , Wassermann A.
Published: May 2003

Furan, pyrrole, and thiophene were polymerized under catalysis by trichloro‐ and trifluoroacetic acid to produce colored polymers which were characterized by various methods, including electronic and proton magnetic resonance spectra and electrical conductances of deeply colored trichloroacetic acid adducts. The predominant repeat units of these polymers are of the same type as those of deeply colored cyclopentadiene polymers, except that a CH2 group is replaced by O, NH, or S.
Grafting in reaction of polyethylene and poly(maleic anhydride)
Authors: Gabara Włodzimierz , Porejko Stanisław
Published: May 2003

Polyethylene has been grafted in a reaction with poly(maleic anhydride) in the presence of radical initiators. The role of oxygen, the comparison of the effectiveness of benzoyl peroxide and AIBN, and the kinetics of the reaction suggest that side chains are formed via a combination of the macroradicals of both polymers.
Grafting of maleic anhydride on polyethylene. I. Mechanism of grafting in a heterogeneous medium in the presence of radical initiators
Authors: Gabara Włodzimierz , Porejko Stanisław
Published: May 2003

Polyethylene has been grafted with maleic anhydride, as proved by the infrared spectra and the properties of the grafted films. The influence of oxygen and a comparison of the effectiveness of benzoyl peroxide and AIBN showed that polyethylene macroradicals are formed through the decomposition of hydroperoxide and peroxide groups. Side chains of poly(maleic anhydride) are formed by a combination of polyethylene macroradicals with those of poly(maleic anhydride). This mechanism of reaction was confirmed by the influence of the amount of film, the initiator and monomer concentrations, and temperature on the percentage of grafting.
Grafting of maleic anhydride on polyethylene. II. Mechanism of grafting in a homogeneous medium in the presence of radical initiators
Authors: Porejko Stanisław , Gabara Włodzimierz , Kulesza Janina
Published: May 2003

Grafting of maleic anhydride on polyethylene is found to take place also in a homogeneous medium. The course of reaction in nitrogen and in air and the influence of temperature of initiator and polymer concentrations suggest that grafting is due to the chain transfer reaction to polyethylene.
Synthesis and polymerization of N‐[1‐(1‐substituted‐2‐oxopropyl)]acrylamides and ‐methacrylamides. copolymerization of these monomers with styrene and substituent effects
Authors: Iwakura Yoshio , Toda Fujio , Suzuki Hideaki
Published: May 2003

The synthesis and polymerization of N‐[1‐(1‐substituted‐2‐oxopropyl)]acrylamides and ‐methacrylamides are described. Seven new monomers were prepared by two kinds of synthetic procedure. The polymerization of these monomers was carried out. Monomer reactivity ratios in the polymerization of these monomers with styrene were determined and the Alfrey‐Price Q and e values calculated. The effects of substituents on the reactivities in copolymerization were observed, and an interpretation of the results is given.
Mechanism of the tertiary amine‐catalyzed dicyandiamide cure of epoxy resins
Authors: Saunders T. F. , Levy M. F. , Serino J. F.
Published: May 2003

Infrared and NMR data on tertiary amine‐catalyzed, dicyandiamide—epoxy resin (and model compound) systems have been utilized to elucidate the mechanism of the curing process. The early exothermic curing reaction is shown to be ring opening of the resin epoxy groups by dicyandiamide imino and amino anionic species, giving rise to N‐alkyl cyanoguanidines; a minor amount of polyether formation also occurs at this time. After the exothermic reaction is essentially complete at <90°C., a slow, high temperature (110–200°C.) addition of hydroxyl hydrogen across the nitrile triple bond occurs, giving rise to an imino ether which then rearranges to the guanyl urea.
Oxidative degradation of polystyrene
Authors: Beachell Harold C. , Smiley Leonard H.
Published: May 2003

Nuclear magnetic resonance, infrared, and ultraviolet spectroscopy were used to elucidate the structure of oxidized polystyrene. To identify the nuclear magnetic resonance peaks of the degraded polystyrene, deuterated polystyrenes were synthesized and degraded. The primary structure present in the degraded polystyrene was found to be an aromatic carbonyl group. It was shown that this structure was formed regardless of the presence of ultraviolet light and was also present when polystyrene was degraded in carbon tetrachloride solution. When polystyrene was degraded in carbon tetrachloride solution, stable polymeric peroxides were formed in a concentration of 4 peroxide groups for every 1000 styrene units.
Influence of addition of olefins on the alternating copolymerization of carbon monoxide and ethylenimine by azobisisobutyronitrile or by γ‐ray irradiation
Authors: Kagiya Tsutomu , Maruta Isao , Ichida Taizo , Narisawa Shizuo , Fukui Kenichi
Published: May 2003

The alternating copolymerization of carbon monoxide and ethylenimine to give poly‐β‐alanine could be initiated by γ‐irradiation but hardly by α,α'‐azobisisobutyronitrile (AIBN). It was found that in the case of the addition of olefin, this system could be copolymerized even by AIBN and that, in the γ‐ray copolymerization of carbon monoxide and ethylenimine, the addition of olefin brought about an increase in the copolymer yield. No difference was observed between the nature of copolymers obtained by AIBN and those obtained by γ‐irradiation, except in the system carbon monoxide–ethylenimine–ethylene. An increase in the amount of reacted olefin gave rise to an increase in copolymer yield. The melting points of the copolymers were in the range 295–335°C. The infrared spectra, x‐ray diffraction diagrams, and NMR spectra of the copolymers were almost identical with that of poly‐β‐alanine obtained by the hydrogen‐migration polymerization of acrylamide. Paper chromatographic analysis of the hydrolysis product of the copolymer showed the existence of β‐alanine, ethylamine, and δ‐aminovaleric acid homolog in the products. From these results, it was concluded that terpolymerization of carbon monoxide, ethylenimine, and olefin took place in the presence of AIBN or γ‐irradiation which gave a crystalline solid copolymer containing the units of nylon 3 and nylon 5. A mechanism of this copolymerization was proposed on the basis of these results.
Preparation of polymeric amines from poly(schiff bases)
Authors: Dyer Elizabeth , Anderson C. Clement
Published: May 2003

A study was made of the preparation of aromatic polymeric amines in order to test their thermal stability. The most useful method was the hydrogenation of polymeric Schiff bases by the dimethylamine—borane reagent or the borane—tetrahydrofuran reagent. The Schiff bases were prepared by the solution polymerization of terephthalaldehyde with various aromatic diamines, including 4,4′‐methylenedianiline, benzidine, and p‐phenylenediamine, and for comparison, 1,6‐hexanediamine. The Schiff bases and the polyamines from the aromatic diamines were found to be dimers or trimers, not high polymers: the polymers from the aliphatic diamine had a degree of polymerization of about 14. Thermogravimetric analyses of the aromatic polyamines under nitrogen showed that the initial temperatures of marked degradation were 350–400°C.
Polymer reactions. VI. Inhibited autoxidation of polypropylene
Authors: Chien J. C. W. , Boss C. R.
Published: May 2003

The autoxidation of polypropylene inhibited by 2,6‐di‐tert‐butyl‐p‐cresol (AH) and dilauryl thiodipropionate (S) was studied by the combined methods of electron spin resonance, oxygen absorption, and chemical analysis. With AH alone, there is a critical concentration of about 6 X 10‐3 mole/l. below which there is no inhibition. This critical concentration agrees with that determined for inhibited squalane autoxidation and that calculated from known rate constants. Above the critical concentration there is a well‐defined induction period during which the ROO· concentration is estimated to be 10‐8 mole/l. [ROOH] decreased rapidly as did [A·] and [AH]; the latter are kinetically related. The rate constant for the reaction between A· and ROO· is estimated to be 7 X 107 l./mole‐sec. at 130°C. At the end of the induction period, [ROOH], [ROO·], and –d[O2]/dt increased rapidly until steady‐state values were attained for all of them. With S alone, there are only retarded oxidation but no well‐defined induction periods. [ROOH] is greatly reduced by S. In all systems where the oxidation rates were appreciably suppressed there was formed a very stable paramagnetic species, S·, which was inert toward AH and I2 but reactive toward triethyl phosphite. Because of its similarity with spin centers in carbon black, S· is postulated to be a delocalized polysulfide spin center. With both S and AH present, the combined effect of stabilization is synergistic. The observed time‐dependent variations of [ROOH], [ROO·], and [A·] follow familiar mechanisms. Mathematical relationships describing each of these three systems are included.
Organic photoconductors. VIII. Photoconductors obtained from the reaction products of poly(9‐vinyl anthracene)
Authors: Morimoto Kazuhisa , Ishida Eisuke , Inami Akira
Published: May 2003

9‐Vinyl anthracene has been polymerized by three methods in cationic systems to obtain organic photoconductors. Cationic polymerization catalysts used were titanium tetrachloride and aluminum chloride anhydride. According to the degree of conversion from poly(9‐vinyl anthracene) to poly(9,10‐dimethylene anthracene) the photosensitivity increased.
Kinetics of polymerization of gaseous formaldehyde
Authors: Boyles James G. , Toby Sidney
Published: May 2003

The polymerization of gaseous monomeric formaldehyde has been studied. The effects of the following variables have been investigated: temperature, initial monomer pressure, surface‐to‐volume ratio of reaction vessel, thickness of polymer deposit, and partial pressure of added oxygen. A three‐step mechanism is proposed which successfully accounts for the results of experiments in which monomer is allowed to deposit on the bare wall of the reaction vessel. When a sufficient amount of polymer has been laid down, the termination reaction becomes negligible and a limiting two‐step mechanism holds. The present results combined with literature values from work done on the depolymerization reaction give the activation energy of the propagation and termination reactions to be 14.2 ± 0.6 and 7.8 ± 0.9 kcal./mole, respectively. Although the reaction is heterogeneous, the activation energies are independent of surface‐to‐volume ratios within the experimental error. The nature of the polymer active sites is considered and these are thought to be hydroxyl groups. The results of work done with added oxygen show a small inhibitory effect.
Dielectric properties of vinylidene chloride–vinyl chloride copolymers
Authors: Kakutani Haruko , Asahina Mitsuo
Published: May 2003

The dielectric properties of vinylidene chloride—vinyl chloride copolymers prepared at conversions of less than 5% were studied. The magnitude of dielectric α absorption (absorption at high temperature) is not a linear function of the composition on account of the effect of the copolymer's crystallinity. On the other hand, a nearly linear relationship was observed between the dielectric glass transition temperature (Tg) of low‐conversion polymer and its composition, while the relationship in a high‐conversion copolymer system, observed by Boyer and Narita et al., is sigmoid. The differences in the temperature—composition relationship between low‐conversion and high‐conversion copolymer systems are illustrated in terms of the distribution of molecular composition. The dielectric β absorption observed in the copolymer whose vinyl chloride molar fraction is more than 0.5 was interpreted as the local motion of vinyl chloride sequences, and the vinyl chloride sequence of 2 or 3 units is sufficient to participate in the β absorption of the copolymer.
Photopolymerization initiated by triphenylphosphine
Authors: Mao T. J. , Eldred R. J.
Published: May 2003

The triphenylphosphine‐initiated photopolymerization of acrylic monomers was studied. Only those monomers containing an α,β‐unsaturated carbonyl group could be photoinitiated by triphenylphosphine, styrene being unaffected at the level of initiator employed. Kinetic studies with methyl methacrylate showed that the propagation was free radical in nature. Analysis of the resulting polymer indicated that it contained one phosphorus atom per chain. Ultraviolet spectral data suggested the formation of complexes between the triphenylphosphine and each monomer for which it is initiator. A relationship between the complex and the polymerization was shown to exist. A mechanism is proposed, involving a light‐activated dipole interaction between the carbonyl oxygen and the phosphorus atom with the ultimate formation of a methacrylate type of free radical.
Studies on the charge‐transfer complex and polymerization. Part XIII. Dilution and solvent effects in radical terpolymerization
Authors: Iwatsuki Shouji , Yamashita Yuya
Published: May 2003

In the terpolymerization of 2‐chloroethyl vinyl ether—maleic anhydride—acrylonitrile and p‐dioxene—maleic anhydride—acrylonitrile systems the compositions of the terpolymers obtained from feed of the same mole fraction were found to be changed beyond the limit of error for the given amounts and kinds of solvent. This change was considered to be divided into two parts. The first part, discussed quantitatively, was due to a dilution effect on the equilibrium complex formation between donor and acceptor monomer, and the second, as tentatively proposed, was due to a solvent effect on the reactivity of the complex.
Cyclopolycondensations
Authors: Kurihara Masaru , Yoda Naoya
Published: May 2003

Fully aromatic polyquinazolinediones of high molecular weight were prepared by the cyclopolycondensation reaction of 4,4′‐diamino‐3,3′‐biphenyldicarboxylic acid with aromatic diisocyanates. The poly(phosphoric acid) solution polymerization techniques yielded tractable poly(urea acid), which was converted to polyquinazolinediones by thermal cyclodehydration at 300–400°C. under reduced pressure. The polyquinazolinediones thus obtained have excellent thermal stability both in nitrogen and in air. The poly(urea acid) is soluble in dimethyl sulfoxide, and films can be cast from the polymer solution of poly(urea acid) (ηinh = 0.8 to 1.8). The films are made tough by being heated in nitrogen or under reduced pressure at 300–400°C. The polymerization mechanism of the cyclopolycondensation reaction was studied, and it was established that the polymerization proceeded through the formation of tractable poly(urea acid), Structure (I), of high molecular weight, followed by cyclodehydration, yielding poly(1,2‐dihydro‐2‐imino‐4H‐3,1‐benzoxazin‐4‐one), Structure (II). On subsequently being heated this undergoes intramolecular rearrangement along the polymer chain, giving the thermodynamically stable polyquinazolinedione, Structure (III).
Analysis of the negative peaks in gel permeation chromatography
Authors: Alliet David
Published: May 2003

The negative peak usually encountered in gel permeation chromatography has been resolved into three distinct peaks through selection of appropriate columns. The three peaks are associated with water, nitrogen, and oxygen. Separation of these simple molecules was found to follow the fundamental theory of gel permeation chromatography, that is, separation according to straight‐chain length.
Multicenter nature of titanium‐based Ziegler–Natta catalysts: Comparison of ethylene and propylene polymerization reactions
Authors: Kissin Yury V.
Published: May 2003

This article discusses the similarities and differences between active centers in propylene and ethylene polymerization reactions over the same Ti‐based catalysts. These correlations were examined by comparing the polymerization kinetics of both monomers over two different Ti‐based catalyst systems, δ‐TiCl3‐AlEt3 and TiCl4/DBP/MgCl2‐AlEt3/PhSi(OEt)3, by comparing the molecular weight distributions of respective polymers, in consecutive ethylene/propylene and propylene/ethylene homopolymerization reactions, and by examining the IR spectra of “impact‐resistant” polypropylene (a mixture of isotactic polypropylene and an ethylene/propylene copolymer). The results of these experiments indicated that Ti‐based catalysts contain two families of active centers. The centers of the first family, which are relatively unstable kinetically, are capable of polymerizing and copolymerizing all olefins. This family includes from four to six populations of centers that differ in their stereospecificity, average molecular weights of polymer molecules they produce, and in the values of reactivity ratios in olefin copolymerization reactions. The centers of the second family (two populations of centers) efficiently polymerize only ethylene. They do not homopolymerize α‐olefins and, if used in ethylene/α‐olefin copolymerization reactions, incorporate α‐olefin molecules very poorly. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1745–1758, 2003
Radical‐initiated polymerization of β‐methyl‐α‐methylene‐γ‐butyrolactone
Authors: Pittman Charles U. , Lee Hookun
Published: May 2003

β‐Methyl‐α‐methylene‐γ‐butyrolactone (MMBL) was synthesized and then was polymerized in an N,N‐dimethylformamide (DMF) solution with 2,2‐azobisisobutyronitrile (AIBN) initiation. The homopolymer of MMBL was soluble in DMF and acetonitrile. MMBL was homopolymerized without competing depolymerization from 50 to 70 °C. The rate of polymerization (Rp) for MMBL followed the kinetic expression Rp = [AIBN]0.54[MMBL]1.04. The overall activation energy was calculated to be 86.9 kJ/mol, kp/kt1/2 was equal to 0.050 (where kp is the rate constant for propagation and kt is the rate constant for termination), and the rate of initiation was 2.17 × 10−8 mol L−1 s−1. The free energy of activation, the activation enthalpy, and the activation entropy were 106.0, 84.1, and 0.0658 kJ mol−1, respectively, for homopolymerization. The initiation efficiency was approximately 1. Styrene and MMBL were copolymerized in DMF solutions at 60 °C with AIBN as the initiator. The reactivity ratios (r1 = 0.22 and r2 = 0.73) for this copolymerization were calculated with the Kelen–Tudos method. The general reactivity parameter Q and the polarity parameter e for MMBL were calculated to be 1.54 and 0.55, respectively. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1759–1777, 2003
Synthesis of functional graft copolymers by solution copolymerization and their evaluation as dispersants in nonaqueous phase dispersion polymerization
Authors: Fujioka Masahiro , Ma Guang‐Hui , Du Yong‐Zhong , Ogino Kenji , Nagai Masatoshi , Omi Shinzo
Published: May 2003

The poly(HEMA‐co‐MMA‐g‐PMMA) graft copolymer was prepared with a poly(methyl methacrylate) (PMMA) macromonomer, 2‐hydroxyethyl methacrylate (HEMA), and methyl methacrylate (MMA), and its application as a dispersant for the nonaqueous phase dispersion polymerization of polystyrene (PST) was investigated. Monodisperse PST particles were obtained with two‐dimensionally tailored graft copolymers, with the number of grafted chains controlled and the polar component (HEMA) in the backbone chains balanced. As for the reactor, a stirred vessel with moderate agitation yielded uniform polymer particles, whereas sealed glass ampules with an overturning motion yielded broader size distributions. Increasing the polarity of the solvent in the continuous phase yielded smaller polymer particles with a gradual deterioration of monodispersity. Uniform polymer particles with a coefficient of variation of less than 6% were obtained up to 30 wt % solid contents. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1788–1798, 2003
Synthesis and nonlinear optical properties of methacrylate polymers based on 2‐[4‐(N‐methyl,N‐hydroxyethylamino)phenylazo]‐phenyl‐6‐nitrobenzoxazole chromophore
Authors: Persico Paola , Centore Roberto , Sirigu Augusto , Casalboni Mauro , Quatela Alessia , Sarcinelli Felice
Published: May 2003

Methacrylate polymers containing different molar contents of nonlinear optical (NLO) active molecular segments based on 2‐[4‐(N‐methyl,N‐hydroxyethylamino)phenylazo]‐phenyl‐6‐nitrobenzoxazole chromophores were synthesized, and their phase behavior and second‐order NLO properties were investigated. Polymers containing 6–17 mol % chromophore segments allowed the preparation of amorphous and optically clear thin films. Some mesomorphic structuration was exhibited by a polymer with 33 mol % chromophoric units. However, this feature did not prevent the possibility of investigating the NLO properties. Nonlinear resonance‐enhanced d33 coefficients were determined by second harmonic generation experiments on spin‐coated, corona‐poled thin films at λ = 1064 nm. Values ranging from 40 to 60 pm/V were measured with increasing chromophore molar contents. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1841–1847, 2003
Effect of the reaction parameters on the particle size in the dispersion polymerization of 2‐hydroxyethyl and glycidyl methacrylate in the presence of a ferrofluid
Authors: Horák Daniel , Semenyuk Nataliya , Lednický František
Published: May 2003

The precipitation of Fe3O4 from an aqueous solution with ammonium hydroxide produced nanoparticles that were coated with a layer of oleic acid [or, in some cases, poly(ethylene oxide) or poly(vinylpyrrolidone)] before their dispersion into the organic phase. The encapsulation of magnetite nanoparticles in poly(2‐hydroxyethyl methacrylate) or poly(2‐hydroxyethyl methacrylate‐co‐glycidyl methacrylate) microparticles was achieved by dispersion polymerization in toluene/2‐methylpropan‐1‐ol. Magnetic poly(glycidyl methacrylate) microparticles were obtained in the presence of poly(ethylene oxide) at the magnetite/monomer interface. The particles containing up to 20 wt % iron maintained their discrete nature and did not aggregate. The effect of the reaction medium polarity, the concentrations of the monomer, initiator, and stabilizer, and the temperature on the particle size, particle size distribution, and iron and oxirane group contents was studied. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1848–1863, 2003