bluuebunny/crossref_metadata_2025 huggingface dataset:
Absolute propagation rate coefficients in radical polymerization from gel permeation chromatography of polymers produced by intermittent initiation
Authors: Hungenberg Klaus‐Dieter , Knoll Konrad , Wulkow Michael
Published: April 2003

The pulsed laser polymerization technique is now a well accepted method to determine propagation rate coefficients for radical polymerization from molar mass distributions resulting from intermittent initiation. A simplified apparatus for the periodic photoinitiation is used which is much less expensive than the laser equipment. The usefulness of the simplified equipment was proved by the determination of kp for styrene at technically relevant temperatures up to 130°C for the first time. Furthermore, careful inspection of the molar mass distribution (mmd) reveals that depending on the reaction conditions, inflection points (Li) can not only be found at integer multiples of kp • to • [M] but also at 0.5i • kp • to • [M], i = 1, 2, 3, … . A rule to find the inflection points leading to correct values for kp is proposed. It is shown that the shape of the mmd inter alia depends on the amount of primary radical termination compared to the termination reaction between growing chains. With dominant primary termination, the maxima of the distribution will give the correct kp, whereas in the absence of primary termination the inflection points should be used. Experimental conditions like initiator concentration, light intensity etc. may influence the position of the Li at least to some extent, and so may give a small but principal error or uncertainty in kp. A new mathematical method for the time‐dependent simulation of the resulting mmd is presented which allows the calculations being performed on a PC within an acceptable time.
The model theory of viscoelastic relaxation properties of bulk cross‐linked polymers. Interchain friction effects
Authors: Gotlib Yuli Ya. , Gurtovenko Andrew A.
Published: April 2003

This article discusses the viscoelastic relaxation properties of bulk cross‐linked polymers. The simple dynamic model of a “mesh‐like” polymer network is considered for the description of the behavior of bulk cross‐linked polymers at stretching. This dynamic network model directly takes into account the following features of bulk polymers: (1) the existence of a fixed average volume of the polymer network, (2) the interconnection between the gradient of the effective viscous medium and the macroscopic deformation of the bulk polymer sample, and (3) the presence of mutual interchain friction. The low‐frequency network dynamics determined by the motions with scales greater than the distance between the network junctions is mostly studied. The simplified “coarse‐grained” cubic network model is used. The total stress which arises in bulk cross‐linked polymers and the viscoelastic functions (the dynamic modulus and viscosity) are calculated. The influence of the interchain friction and of the fixed average volume of the network on the total stress and on the dynamic modulus and viscosity is discussed. The results obtained are compared with the results of the theoretical approaches developed earlier.
Non‐uniqueness in determination of terminal and penultimate model reactivity ratios in the styrene‐methyl methacrylate free‐radical copolymerization system
Authors: Kaim Andrzej , Oracz Paweł
Published: April 2003

The terminal and penultimate model reactivity ratios in the free‐radical copolymerization of styrene and methyl methacrylate in bulk at 40°C were calculated by means of the simplex and scanning methods. Calculations showed that for the terminal model r1 and r2 vary in comparatively narrow ranges of 0.548–0.552 and 0.480–0.483, respectively. For the penultimate model, the most accurate reactivity ratios calculated by the simplex method, which were r11 = 0.727, r22 = 0.490, r21 = 2.890, r12 = 4.583, are surrounded with sets of reactivity ratio values of equal accuracy. The ranges of variation were found to be 0.711–0.746, 0.487–0.492, 2.810–2.970 and 4.213–5.049, respectively. Numerical values of the penultimate r‐parameters calculated with the simplex method depend, due to the structure of the multidimensional space (r11, r22, r21, r12, σ), on the initial guess for the r‐parameters. Use of the covariance matrix for the estimation of the indetermination ranges is discussed.
The chemical composition component of the distribution of chain length and long chain branching for copolymerization of olefins and polyolefin chains containing terminal double‐bonds
Authors: Soares João B. P. , Hamielec Archie E.
Published: April 2003

An analytical solution for the distribution of molecular weight, long chain branching and chemical composition of polyolefins produced under steady‐state conditions with the mechanism of terminal branching is derived. The model predictions agree well with Monte‐Carlo simulation results. This detailed description of the microstructure of polymer chain populations with different levels of long chain branching can be useful in establishing structure‐property relations for these polymers.
Mean‐square radius of gyration of polymer chains
Authors: Zhou Zhiping , Yan Deyue
Published: April 2003

The calculations of the mean‐square radius of gyration for more than thirty sorts of polymer chains are reviewed on the basis of a unified approach. A general expression of the mean‐square radius of gyration was developed for polymer chains with side groups and/or heteroatoms. It consists of two parts. The first part is the mean‐square radius of gyration of a model chain, in which every side group, R, was considered to be located in the centroid of the substituent flanking the related skeletal atom, and the second one is the total contribution of the square radius of gyration of every substituent around its centroid. Numerical calculations showed that the logarithmic relationship between the mean‐square radius of gyration and the degree of polymerization becomes linear when x is greater than 100, and the dependence of the mean‐square radius of gyration on the molecular weight can be expressed by the general formula 〈S2〉 = aMb, which was supported by a number of experimental measurements. A comparison of our expression for the mean‐square radius of gyration with that reported by Flory was made. The difference is obvious in the range of lower molecular weight, and gradually declines with increasing degree of polymerization.
The “fast” and “slow” mode theories of interdiffusion in polymer mixtures: Resolution of a controversy
Authors: Akcasu A. Ziya
Published: April 2003

The theory of interdiffusion of a pair of components in multicomponent polymer mixtures is reviewed from a statistical point of view, and the foundation of the “fast” and “slow” mode theories, as well as the more recent “ANK” theory of interdiffusion is critically examined. The ANK theory reproduces the results of the slow and fast mode theories as the two limits when the vacancy concentration is varied from zero to a large value, and shows that the interdiffusion coefficient in a binary compressible mixture at finite vacancy concentrations can not in general be expressed only in terms of the tracer diffusion coefficients of the components, but it involves in addition the cooperative diffusion coefficient which characterizes the relaxation of total density fluctuations. The predictions of the ANK expression for the molecular dependence of the kinetic factor is compared with recent scattering experiments.
The role of the orientation tensor in the rheology of flexible polymers
Authors: Wagner Manfred H. , Geiger Kalman
Published: April 2003

The stress‐strain relations for transversely isotropic deformations of linear and branched polymer melts as well as of (crosslinked) rubbers are discussed in terms of the orientation tensor. It is shown that orientation and network strand extension are decoupled, and that the relative tube diameter and its inverse, the molecular stress function f, can be extracted directly from experimental data, if the effect of network orientation is accounted for by the order parameter. The tension of the average network strand increases with increasing deformation. This is caused by an increasing restriction of lateral movement of polymer chains due to deformation. At small strains, f2 is found to be linear in the average stretch for melts as well as for rubbers, which corresponds to a constant volume of the tube. At large strains, melts show maximum molecular tension, depending on the degree of longchain branching, while rubbers show maximum extensibility.
Application of molecular mechanics to refine and understand the crystal structure of polythiophene and its oligomers
Authors: Ferro Dino R. , Porzio William , Destri Silvia , Ragazzi Massimo , Brückner Sergio
Published: April 2003

A molecular mechanics computational procedure, previously used for the refinement and the analysis of several crystalline polymers, was applied to investigate the crystal structures of the tetramer (T4) and hexamer (T6) of thiophene, as well as the crystal structure of polythiophene (PT). Simultaneous minimization of intra‐ and intermolecular energies of the T4 and T6 structures, obtained by Rietveld analysis of powder X‐ray diffraction profiles, leads to molecular conformations showing smaller deviations from the ring co‐planarity than the original models. For both oligomers the calculations confirm that the molecular centre of inversion is not a crystallographic centre of symmetry, as also revealed by X‐ray diffraction of the T6 single crystal. This surprising effect appears to arise from intermolecular interactions between the terminal residues, hence is not relevant with respect to the PT polymer structure. The small energy cost for constraining the molecules at the crystallographic centre of symmetry is in agreement with experimental findings that reveal the existence of polymorphs for both T4 and T6. The calculations on the T6 single crystal were used to upgrade the MM2‐like force field, which was then used to determine the minimum‐energy model of the monoclinic crystal structure of polythiophene.
Atomistic computer simulation of mechanical properties of composites
Authors: Steinfath Matthias , Bruns Wolfgang
Published: April 2003

An atomistic computer simulation is performed in order to investigate structure and mechanical behaviour of materials composed of fibres embedded in a polymer matrix. A graphite‐poly(propylene) system is used as a model, the energy of which has been minimized. Unlike the models of other authors the bond angles of the polymer chains are assumed as flexible. The properties found were compared with those of the bulk polymer. The results show that the presence of the graphite surface affects the structure of the polymer as well as the values of the elastic constants within a layer of 7 Å thickness. In this layer the density has a maximum and the chain segments are oriented parallel by the graphite plane. A long range order, however, cannot be observed.
Styrene‐methyl methacrylate copolymer microstructure according to terminal and penultimate model for free‐radical copolymerization
Authors: Kaim Andrzej
Published: April 2003

Microstructure of styrene‐methyl methacrylate copolymers was determined according to the “bootstrap model” description using the terminal and the penultimate model of copolymerization. The implication of non‐uniqueness in determining the penultimate model reactivity ratios from the copolymer microstructure is discussed. The styrene centred triad sequences in the copolymer obtained in the free‐radical copolymerization of styrene and methyl methacrylate in bulk at 40°C were calculated using various sets of terminal and penultimate model reactivity ratios with very similar standard deviations. Calculations showed that for both models, the terminal model and the penultimate model, different reactivity ratios with very similar standard deviations are equally well suited for the quantitative description of the triad sequence distribution in the copolymer. The terminal and penultimate models produce different styrene centred triad sequence distributions in the copolymer, the difference depending on the penultimate model reactivity ratios used for calculation and on the type of the styrene centred triad sequence. The best equivalence of the two kinetic models was found when the initial r‐parameters guess used for determining the penultimate reactivity ratios by the simplex method were r11 = r21 = r1 and r22 = r12 = r2. The results suggest that the penultimate effect on the styrene‐methyl methacrylate free‐radical copolymerization system is limited.
Fractal models of the shrinkage compensation mechanism for unsaturated polyesters
Authors: Merle Gérard , Vincent Nicole
Published: April 2003

The shrinkage compensation mechanism in sheet molding compounds is governed by the morphology resulting from phase separation and microvoids formation. The observed microvoid morphology is quantified by using fractal geometry, in 2D and 3D spaces. The correlation between the morphologies of the matrix with phase separation and those of the microvoids is demonstrated by simulation. The pressure effect is studied. The fact that the shrinkage compensation has a pressure dependent optimum is explained by a model for the compensated volume. Thus, the “fractal pillar effect” is a model that represents properly speaking the compromise between pressure and volume creation shown by such a smart material.
Simulations of rodlike molecules represented by anisotropic Lennard‐Jones potentials
Authors: Tanaka Genzo , Mattice Wayne L.
Published: April 2003

In the interests of carrying out computer simulations efficiently for systems of rodlike molecules, the model proposed by Berne and coworkers, in which each rod is represented by an anisotropic Lennard‐Jones potential, was extensively compared with a site‐site model. Using this potential, Monte Carlo simulations were carried out for rodlike molecules with aspect ratio (Ra) ranging from 3 to 50. Short rods such as Ra < 10 exhibit an isotropic phase for essentially the entire range of volume fraction ϕ, while long ones (Ra > 20) show an isotropic phase at only very low ϕ < 0.07. The attractive part of the potential makes rodlike molecules associate as well as align even at low ϕ. At high ϕ around or above the transition, the repulsive potential dominates and the attractive potential becomes secondary. Based on simulation results, some implications for designing molecular composites are offered.
Kinetics of spinodal decomposition in mixtures of low molecular weight liquid crystals and flexible polymers
Authors: Lin Zhiqun , Zhang Hongdong , Yang Yuliang
Published: April 2003

In this paper, the time‐dependent Ginzburg‐Landau model for mixtures containing nematogens has been applied to mixtures of low molecular weight liquid crystals and flexible polymers. Dynamic equations for the time evolution of concentration and orientation fluctuations and the structure factors for these fluctuations are given. It is shown that the coupling between concentration and orientation fluctuations is absent in the isotropic spinodal region, thus the evolution of the structure factors for the concentration fluctuations falls into the Cahn‐Hilliard classic category and it exhibits no maximum in the structure factors of orientation fluctuations. We should emphasize that, in the anisotropic spinodal region, both concentration and orientation structure factors possess a maximum but not coincide with each other and both are shifting to smaller wave numbers according to the scaling relation, qmax ˜ τ−α, as time increases. The value of a closely correlates to the interfacial free‐energy parameters.
Open three‐dimensional unhindered molecular chains: Partition function
Authors: Alvarez‐Estrada Ramón F.
Published: April 2003

An open molecular chain, formed by N classical particles moving in three dimensions and having N − 1 bonds of constant lengths between successive neighbours, is considered. Hamiltonian methods with manifest rotational invariance allow to characterize all constraints. The classical partition function, Z0, for a large open chain in thermal equilibrium is analyzed in general. Simpler integral representations for Z0 are obtained, with the following advantages: (i) explicit rotational invariance in the integrands, (ii) only tridiagonal matrices appear and, moreover, approximations for their determinants can be obtained. For a two‐dimensional open chain, an approximate factorized formula for Z0 is presented, and its essentials are generalized to the three‐dimensional case. In both cases, the features of the partition functions bear certain similarities to that for a classical ideal gas. The approximate partition functions lead to approximate analytical computations of the correlations between pairs of different bond vectors, of the squared end‐to‐end distance, of the probability distribution for the end‐to‐end vector and of the structure factor, which display some novel features. Some comparisons with the corresponding results for the Gaussian chain are made.
Congenital myopathies at their molecular dawning
Authors: Goebel Hans H.
Published: April 2003

The introduction and application of molecular techniques have commenced to influence and alter the nosology of congenital myopathies. Long‐known entities such as nemaline myopathies, core diseases, and desmin‐related myopathies have now been found to be caused by unequivocal mutations. Several of these mutations and their genes have been identified by analyzing aggregates of proteins within muscle fibers as a morphological hallmark as in desminopathy and actinopathy, the latter a subtype among the nemaline myopathies. Immunohistochemistry has played a crucial role in recognizing this new group of protein aggregate myopathies within the spectrum of congenital myopathies. It is to be expected that other congenital myopathies marked by inclusion bodies may turn out to be such protein aggregate myopathies, depending on analysis of individual proteins within these protein aggregates and their association with putative gene mutations. Muscle Nerve 27: 527–548, 2003
Rituximab in the treatment of polyneuropathy associated with anti‐MAG antibodies
Authors: Renaud Susanne , Gregor Michael , Fuhr Peter , Lorenz Delia , Deuschl Günther , Gratwohl Alois , Steck Andreas J.
Published: April 2003

No causative or curative therapy exists for the polyneuropathy associated with antibodies to myelin‐associated glycoprotein (anti‐MAG). Rituximab is a mouse‐human chimeric antibody that specifically eliminates B‐cells and B‐cell precursors. Preliminary results suggest a beneficial effect on antibody‐dependent autoimmune diseases. Nine patients with an anti‐MAG–associated IgM polyneuropathy received rituximab once weekly for 4 weeks. In all patients, the number of B‐cells in the peripheral blood declined below levels of detection, and the IgM levels decreased between 35% and 82% (median, 58%). In eight patients, lowering of the anti‐MAG antibody titers of more than 52% was observed. Clinical status improved in six patients, remained stable in two, and worsened in one. The motor nerve conduction velocity improved by at least 10% in one ulnar nerve in seven patients and worsened in two. Rituximab was well tolerated and is a promising new drug in the treatment of patients with anti‐MAG–associated polyneuropathy. Muscle Nerve 27:611–615, 2003
S‐protein is expressed in necrotic fibers in Duchenne muscular dystrophy and polymyositis
Authors: Louboutin Jean‐Pierre , Navenot Jean‐Marc , Rouger Karl , Blanchard Dominique
Published: April 2003

Complement regulatory proteins (CD55, CD59) and a fluid‐phase complement regulator (S‐protein) expression and distribution were studied in Duchenne muscular dystrophy (DMD) and polymyositis by Western blots and immunocytochemistry. In muscle samples from control subjects, no specific signal was detected for CD55 or S‐protein, and CD59 was present on the sarcolemma of the muscle fibers. In DMD and polymyositis, Western blots demonstrated a 18–20 kDa band corresponding to CD59, as well as a signal corresponding to S‐protein. Immunocytochemistry showed a colocalization between complement membrane attack complex (MAC), a molecule previously demonstrated in necrotic muscle fibers in DMD and polymyositis, and S‐protein in necrotic fibers of DMD and polymyositis. Necrotic muscle fibers were more numerous in muscle biopsies of DMD patients with stronger signals for S‐protein in Western blots. These results suggest that S‐protein is not able to prevent the full assembly of MAC in necrotic fibers of patients with DMD and polymyositis, but might instead inactivate MAC deposits present inside necrotic fibers or participate in the clearance of MAC‐attacked muscle fibers. Muscle Nerve 27: 575–581, 2003
Is quantitation necessary for assessment of sural nerve biopsies?
Authors: Pamphlett Roger , Sjarif Adrian
Published: April 2003

In this study we measured the reliability and accuracy of visual assessment of certain features of sural nerve pathology. Three raters visually assessed 20 sural nerves over two sessions. Four features were categorized: (1) myelinated fiber (MF) density; (2) size loss of MFs; (3) thinly myelinated axons; and (4) axonal clusters. Intra‐ and interrater reliabilities for the categories were determined. Quantitative data were compared with the visual assessments. Percentage agreements for single raters between the two sessions ranged from 35% to 100% and 9 times out of 12 were ≥70%. Interrater reliability, however, showed a kappa‐value range of 0.03 (poor) to 0.49 (medium). In 85% of cases, visual ratings were within one category of the quantitated MF loss. However, visual categorization was poor compared with quantitation for determining size loss of MFs and myelin thickness. Quantitation needs to be considered to aid peripheral nerve pathologists in the assessment of some of the features of sural nerve biopsy specimens. Muscle Nerve 27: 562–569, 2003
Self‐inflicted tourniquet paralysis mimicking acute demyelinating polyneuropathy
Authors: Storm S. , Weiss M. D.
Published: April 2003

Tourniquet paralysis is an uncommon complication of surgery, and self‐inflicted tourniquet paralysis has never been documented to our knowledge. We report a patient with bilateral self‐induced tourniquet paralysis of the lower extremities, whose symptoms were initially attributed to an acute demyelinating sensorimotor polyneuropathy based on clinical presentation and electrodiagnostic study. After investigations failed to reveal a cause, he was found to have placed tourniquets on his legs because of a rare obsession with limb amputation known as apotemnophilia. Significant spontaneous partial resolution of clinical symptoms was noted after 6 weeks. Electrophysiologic evidence of segmental demyelination of multiple motor nerves localized to the same region may help to distinguish this condition from other forms of acute demyelinating polyneuropathy. Muscle Nerve 27: 631–635
, 2003
Intravesical electrical stimulation in the treatment of micturition dysfunction in children
Authors: Gladh Gunilla , Mattsson Sven , Lindström Sivert
Published: April 2003

Aims

To evaluate the results of intravesical electrical stimulation (IVES) in an open prospective study to treat underactive detrusor in children. The treatment was offered as an alternative to clean intermittent catheterization (CIC).

Methods

Forty‐four children were included, 21 girls and 3 boys (6–16 years, md 10) with idiopathic, 9 girls and 11 boys (4–18 years; md 13) with neurogenic underactive detrusor. IVES was given by a catheter electrode in the bladder (cathode) with the anode attached to the suprapubic abdominal skin. Continuous stimulation at 20 or 25 Hz was delivered by battery powered stimulators giving unipolar square‐wave pulses (0,2 or 0,7 ms). Stimulation intensity was adjusted individually according to the acceptance of the child (12–64 mA). IVES was initially given at the clinic but 18 children had additional treatment at home. Effect of treatment was monitored by micturiton/incontinence diary, reports of bladder sensation, recordings of urinary flow, residual volume and frequency of urinary tract infections.

Results

The IVES‐treatment was completed by 39/44 children. Long term normalization of the voiding (md 2,5 years follow up) was obtained for 20/24 children with idiopathic problems (83%) and 8/20 with neurogenic problems (40%). Another four had much improved bladder function. The neurogenic group required more stimulation sessions than the idiopathic group. Of those on CIC, 11/15 who completed IVES could discontinue the catheterization. The frequency of urinary tract infections and incontinence decreased significantly (P < 0.01).

Conclusions

It is concluded that IVES is a promising method to treat the underactive detrusor in children. Neurourol. Urodynam. 22:233–242, 2003. © 2003 Wiley‐Liss, Inc.
Changes in bladder neck geometry and closure pressure after midurethral anchoring suggest a musculoelastic mechanism activates closure
Authors: Petros Peter
Published: April 2003

Aims

The aim of this study was to investigate the anatomical origins and clinical significance of cough pressure transmission ratio (CTR) by using virtual‐operation (VO) techniques.

Methods

Thirty‐four patients underwent perineal ultrasound examination, standard urethral pressure cough testing both with and without unilateral midurethral anchoring (VO), all tests being performed without urethral elevation. In eight patients where there was no change in CTR, a one‐sided fold of suburethral vagina (VO) was taken (pinch test) and the CTR repeated.

Results

After midurethral anchoring, maximal urethral pressure increased from a mean of 33.25 cm H2O to a mean of 58.06 cm H2O (P < 0.0001) and restoration of anatomy was noted in all 11 patients who had obvious funneling on straining. Conversion of a <100% CTR to >100% CTR in the proximal urethra was observed in 14 of 22 patients (P < 0.005), with no significant change noted in the distal urethra. Further conversion of CTR was noted in six of the remaining eight patients with unilateral plication of suburethral vagina (pinch test).

Conclusions

A musculoelastic closure mechanism most likely activates urethral closure. CTR is most likely an index of changed intraurethral area, not necessarily closure, and may be a more sensitive objective test than perineal ultrasound for diagnosing urethral narrowing, especially when used with virtual‐operation techniques. Neurourol. Urodynam. 22:191–197, 2003. © 2003 Wiley‐Liss, Inc.
Bladder pressure monitoring during intermittent catheterization: A comparison of gauges and methods
Authors: Ferguson Corri L. , Walter James S. , Lucero Yuonne , Wheeler John S. , Damaser Margot S.
Published: April 2003

Aims

We previously have investigated a technique for serial bladder pressure measurements in patients with spinal cord injury (SCI) using intermittent catheterization. In the current study, we compared an FDA‐approved digital gauge with the previously studied analog gauge and studied the effects of hydrostatic pressure differences.

Methods

Either a digital or an analog pressure gauge was attached to each subject's catheter just before bladder catheterization. Both immediate and stable pressures were recorded. The bladder was then drained until nearly empty and pressure was again recorded (almost empty bladder pressure). Detrusor pressure was estimated as full minus almost empty bladder pressure. Bladder pressures greater than 40 cm H2O were presumed to represent bladder contractions. To investigate the effects of hydrostatic pressure, additional measurements, adjusting the level of the air–urine meniscus, were obtained in three subjects.

Results

Recordings were made from nine SCI subjects using both gauges. Estimates of detrusor pressure, with and without bladder contractions, and associated bladder volumes, were not significantly different between digital and analog gauges. In the absence of bladder contractions, detrusor pressure with the meniscus at the end of the catheter (5 ± 1 cm H2O) was significantly lower than that recorded with no adjustment of the urine meniscus (12 ± 1 cm H2O).

Conclusions

Standardizing measurement techniques to equalize hydrostatic pressures should facilitate reliable estimates of detrusor pressure. Frequent monitoring of bladder pressure using this technique may assist with the urological care of SCI patients. Neurourol. Urodynam. 22:250–254, 2003. Published 2003 Wiley‐Liss, Inc.
Women's knowledge, practises, and intentions regarding correct pelvic floor exercises
Authors: Chiarelli Pauline , Murphy Barbara , Cockburn Jill
Published: April 2003

Aim

Although research has demonstrated the efficacy of pelvic floor exercises (PFXs) for the prevention and treatment of female urinary incontinence (FUI), adherence to PFX regimens is commonly poor. There is some evidence that this finding is in part due to a lack of knowledge about how to perform PFXs correctly and misconceptions about the required frequency and duration of PFX regimens.

Methods

By using a sample of 720 postpartum women, this study investigates women's PFX regimens both before and during pregnancy and postpartum.

Results

Findings demonstrated that most women were aware of the required frequency for PFXs (at least every second day): just over half had done them this often during pregnancy and 91% intended to do so postpartum. However, few had done them at this level before pregnancy and less than half knew that PFXs should be carried out indefinitely throughout the lifetime. Moreover, only two thirds were confident that they were doing PFXs correctly.

Conclusion

The findings suggest that, despite good knowledge of the required frequency of PFXs, few women practise them regularly over their lifetime, many apparently perceiving PFXs as relevant only to the childbirth years. Implications for health professionals in addressing these gaps in women's knowledge and practises are discussed. Neurourol. Urodynam. 22:246–249, 2003. © 2003 Wiley‐Liss, Inc.
Ionic miscibility enhancement via microion elimination in sulfonated polystyrene/poly(ethyl‐acrylate‐co‐4‐vinyl pyridine) ionomer blends
Authors: Zhang Xinsheng , Eisenberg Adi
Published: April 2003

Miscibility enhancement of ionomer/ionomer and ionomer/polymeric acid systems is studied on the polymer pairs of poly(styrene‐co‐tetramethyl ammonium styrenesulfonate)/poly(ethyl acrylate‐co‐N‐methyl‐4‐vinylpyridinium iodide) and poly(styrene‐co‐styrenesulfonic acid)/poly(ethyl acrylate‐co‐N‐methyl‐4‐vinylpyridinium iodide). NMR and dynamic mechanical results show that in these blends direct macroion–macroion interaction can be achieved with the elimination of microcounterions from the polymer chains. Ion‐ion attraction leads to a miscibility enhancement comparable to that of the previously reported proton transfer blends; a miscible blend is obtained with ca. 5 mol% of ions in the polymers.
High intrinsic conductivity in ladder type polymers: Pyrolyzed BBB
Authors: Davidov D. , Belaish I. , Rettori C. , McLean M. R. , Dalton L. R.
Published: April 2003

Through electrical conductivity and ESR measurements of heat treated BBB‐rigid‐rod ladder polymers, we provide evidence for the existence of an irreversible transformation to another cross‐linked ladder polymer with high intrinsic conductivity. The transformation occurs at a pyrolysis temperature, Tp ≅ 680°C. The results suggest a novel transport mechanism.
Synthesis, polymerization and cation conductive properties of (ω‐carboxy)‐oligo(oxyethylene) methacrylate
Authors: Takeoka Shinji , Maeda Yoshinari , Tsuchida Eishun , Ohno Hiroyuki
Published: April 2003

Alkali‐metal salts of (ω‐carboxy)oligo(oxyethylene) methacrylate (CME12M, M = Li or Cs) have been synthesized and polymerized to prepare solid polymer electrolytes. These types of solid polymer electgrolytes provide a homogeneous phase, since these polymers have a flexible main chain, an oligo(oxyethylene) side chain for ion conduction, and a carrier ion source in one repeating unit. The AC conductivity of P(CME12Li) homopolymer is 8.9 × 10−9 S cm−1 at 30°C, while that of P(CME12Cs) is 3.3 × 10−6 S cm−1 at 30°C, which is the highest value among single ion conductors, have been reported as polyelectrolyte “homopolymer” without any additives. High ionic conduction of P(CME12Cs) is due to low glass transition temperature (Tg = −54°C) and weaker ion–ion and ion–dipole interaction of Cs+ than that of Li+.
Phase separation during the chemical blending of polybutadiene/polystyrene blend
Authors: Nam Dong Ki , Kim Sung Chul
Published: April 2003

Phase separation behavior of the chemical blending of the polybutadiene (PBD)/polystyrene (PS) was investigated by the light scattering technique. Polybutadiene was dissolved in the styrene monomer and the polymerization of the styrene monomer was carried out thermally in the presence of the dissolved polybutadiene. The effect of the PBD composition, synthesis temperature and the PS crosslink density on the phase separtion behavior were analyzed. The mixture of PBD/PS/styrene monomer showed UCST (upper critical solution temperature) character. It was found that the phase separation was proceeded by the nucleation and growth mechanism in the early stage of polymerization. The time (t) dependence of the domain correlation length (dm) could be represented by a power law in the late stage of the phase separation. The crosslinking of PS hindered phase separation in the coalescence process.
Fluorescence study of polyelectrolyte complex formation I: complexation of anthracene‐loaded poly(methacrylic acid) with polycations
Authors: Itoh Yoshihiro , Negishi Kazuhiko , Lizuka Eisaku , Abe Koji
Published: April 2003

Poly(methacrylic acid) containing 0.4 mol% of anthryl groups (PMA‐A) was prepared and its formation of polyelectrolyte complex (PEC) with some polycations in aqueous solution was investigated. The fluorescence intensity of the anthracene (Anth) chromophore increases with the formation of PEC, which may be caused by enhanced hydrophobicity of the microenvironment around the Anth moiety. The intensity depends strongly on the chemical structures and properties of polycations (integral or pendant type, flexibility and hydrophobicity of polymer chains, etc.) and on the experimental conditions (pH and ionic strength).
Ionic conductive polymers based on polymethylsiloxane graft‐crosslinked with oligo(ethylene oxide)
Authors: Mei Henry L. , Okamoto Yoshiyuki , Skotheim Terje
Published: April 2003

Polymethylsiloxane graft‐crosslinked with oligo(ethylene oxide) (EO) was synthesized and characterized. The polymer was an elastic solid and stable to hydrolysis. Polymer/salt complexes were formed on mixing with lithium trifluoromethane‐sulfonate(LiCF3SO3). The ionic conductivity of the complexes was measured by complex impedance method and the conductivity reached 6 × 10−5 S cm−1 at 25°C and 1.5 × 10−4 S cm−1 at 40°C. The effect of salt concentration, crosslinking, length of EO units and moisture content on the conductivity were investigated. Glass transition temperature and thermal stability of the polymer and the polymer/salt complexes were determined by differential scanning calorimeter and thermogravimetric analysis measurements.
Water‐soluble polyamides as potential drug carriers, IV: amine‐functionalized copolyaspartamides
Authors: de L. Machado Maria , Neuse Eberhard W. , Perlwitz Axel G. , Schmitt Siegfried
Published: April 2003

Poly‐D,L‐succinimide (1) is converted to copolyaspartamides of the general type2by sequential treatment with diamine nucleophiles R′NH2and R″NH2, in which R′ is a group containing a tertiary amine function providing water solubility, and R″ represents a substituent comprising primary or secondary amino groups capable of interaction with suitably carboxyl‐ or carbonyl‐functionalized drug models. The reactions are performed in dimethylformamide medium under mild, yet carefully controlled conditions conducive to aminolytic imide ring opening in the educt polymer without causing crosslink formation through difunctional interaction of the R″NH2co‐nucleophile. The perfectly water‐soluble polymeric products (ηinn, 5–30 ml/g), purified and isolated by dialysis (12,000–14,000 molecular mass cut‐off) and freeze‐drying, are of interest as macromolecular carrier species for pharmaceuticals and other biologically active agents. The drug‐binding potential of the target polymers is demonstrated by the coupling, through active ester intermediacy, of phenylacetic acid as a representative drug model to selected copolyamides.
Solubility of methacrylic acid alkali metal salts in polyethylene oxide and cation conductivity after polymerization
Authors: Ohno Hiroyuki , Ito Yasushi
Published: April 2003

Methacrylic acid alkali metal salts (MAAM; M = Li, Na, K, Rb, or Cs) were dissolved in polyethylene oxide, and in situ polymerization was carried out. The solubility of these salt monomers in PEO oligomers increased with the ionic radius of the cation. Their solubility decreased with an increase in the average molecular weight of PEO oligomers, suggesting the considerable contribution of terminal hydroxyl groups of PEO to the solubilization of these salt monomers. The polymerization of MAAM in PEO induced a slight increase of turbidity. The PEO (molecular weight = 200) system containing P(MAAM) shows an ionic conductivity of 1–5 × 10−4 S/cm depending on the cation species. The P(MAAM)/PEO systems having larger cations such as Rb or Cs as the mobile ion show higher ionic conductivity, and a clear relationship was obtained between conductivity and cation radius. This tendency cannot be explained by the ordinary migration model of ions as being either naked or solvated. The fact that the systems having larger cations show higher conductivity can be explained by the following two reasons: the interaction force with the polymer matrix is weaker, and the dissociation energy is lower. The former reason should be dominant, because considerable differences in the ionic conductivity cannot be explained fully by differences in the lattice energy only. Similar experiments were carried out in poly[(oligooxyethylene) methacrylate] (P(MEO)). However, the ionic conductivity of the product remained at around 10−6 S/cm, the observed tendency between the ionic conductivity and the cation radius was quite similar, suggesting the same mechanism as in PEO.
Preparation of photochromic polymers by stereospecific copolymerization of trans‐4‐(2‐methacryloxyethyloxy)azobenzene and (−)‐menthyl methacrylate
Authors: Altomare A. , Ciardelli F. , Lima R. , Solaro R.
Published: April 2003

The synthesis is reported of a new photochromic monomer, trans‐4‐(2‐methacryloxyethyloxy) azobenzene (MEAB), where the azobenzene chromophore is separated from the ester group by an ethylenoxy spacer arm. Comparative experiments show that trans‐4‐methacryloxyazobenzene (MAB), having the azobenzene group directly attached to the ester functionality, does not homopolymerize or copolymerize with (−)‐menthyl methacrylate (MnMA) in the presence of different anionic initiators, whereas isotactic homopolymers and copolymers of MEAB can be obtained: the microstructure is described with reference to analogous atactic macromolecules.
Radiation resistance and molecular structure of poly(arylene ether sulfone)s
Authors: Hill David J. T. , Lewis David A. , O'Donnell James H. , Pomery Peter J. , Hedrick James L. , McGrath James E.
Published: April 2003

The radiation resistance of a series of aromatic polysulfones comprising alternating units of diphenyl sulfone and various aromatic diols has been investigated by measuring volatile products, soluble fractions and electron spin resonance (ESR) spectra. The yields of radicals at 77 K observed by ESR and of SO2 at 423 K have indicated that biphenol gives enhanced resistance to Y radiation, and tetramethyl bisphenol‐A decreased resistance, relative to bisphenol‐A, bisphenol‐S and hydroquinone. The protective effect of bisphenol was confirmed by lower scission and crosslinking yields determined from the soluble fractions after high doses.
Mechanical properties of solvolysis lignin‐derived polyurethanes
Authors: Nakamura Kunio , Mörck Roland , Reimann Anders , Kringstad Knut P. , Hatakeyama Hyoe
Published: April 2003

In order to study the tensile properties of solvolysis lignin polyurethanes, polyurethane (PU) films were prepared from the solvolysis lignin (SL)–polyethylene glycol (PEG)–diphenylmethane diisocyanate (MDI) system, and in addition to this further PU films were also prepared from the SL–MDI system. In the SL–PEG‐MDI system, the SL content, the molecular weight of PEG and the NCO:OH ratio were varied in order to control the physical properties. The tensile stress and Young's modulus of the PUs of the SL–PEG–MDI type increased with increasing SL content and NCO:OH ratio. The tensile properties of the PUs from the SL–MDI system showed no NCO:OH ratio dependency; i.e. the mechanical properties of PUs are not influenced by the change in crosslinking. It is possible to control the tensile properties of PUs of the SL–PEG–MDI type by changing the content of PEG and SL at a constant NCO:OH ratio.
Processable polyisoimide polymer blends for application as thermally stable adhesives for composites and advanced metal alloys
Authors: Boschan R. H. , Landis A. L. , Lau K. S. Y. , Quezada S. , Tajima Y. A.
Published: April 2003

Polyimides are effective thermally stable bonding agents for substrates including titanium, aluminum alloys, steel alloys, metal matrix composites, and polymer/fiber composites with good tolerance toward elevated temperature and humidity.

Problems associated with polyimide adhesives, including high processing temperatures and pressures and high melt viscosity, can be partially or totally alleviated by use of blends of polyisoimides. During thermal processing, the polyisoimides are isomerized to their polyimide modifications.
Fluorescence characteristics of europium ions stabilized in solid polymer electrolytes containing polyether structure
Authors: Ohno Hiroyuki , Lau Sim Peng
Published: April 2003

Polyethylene oxide (PEO) oligomers can dissolve lanthanide salts. The terminal hydroxyl groups of PEO affect the solubility of the lanthanide salts in the PEO considerably. However, no intensive fluorescence was observed from Eu3+ dispersed in PEO or other ion‐conductive polymers containing terminal hydroxyl groups, because of the quenching effect of the terminal hydroxyl groups. Copolymer of ω‐methoxy oligo(oxyethylene) methacrylate and methyl methacrylate (P(MEOM‐co‐MMA)) could dissolve small amount of Eu(NO3)3, but the copolymer film containing Eu3+ shows intensive fluorescence (Ex = 269.0 nm, Em = 570.0 nm). This was prepared as a soft film, and there was a clear dependence of the Eu3+ concentration on the fluorescence intensity. A linear relation between the film thickness and the fluorescence intensity was also observed. Little fluorescence was found for Eu3+ in the blend of the corresponding two homopolymers, i.e. poly‐(ω‐methoxy oligo (oxyethylene) methacrylate) (PMEOM) and poly(α‐methyl methacrylate) (PMMA). This strongly suggests that intensive fluorescence requires a mixed state of MEOM and MMA units at molecular level.
Effect of substituent groups of diphenyl disulfide on novel cationic oxidative polymerization: examination of the electrophilic reaction of the cation by computational calculation
Authors: Shouji E. , Yamamoto K. , Katoh J. , Nishide H. , Tsuchida E.
Published: April 2003

Substituent groups of the diphenyl disulfides (DPSs) influence the cationic oxidative polymerization in the formation of polyphenylene sulfides (PPSs). A semiempirical MO calculation (AM1) was performed on the model compounds of PPS, such as thioanisoles (TAs) and diphenyl sulfides (PSs), in order to elucidate the reactivity of the cation. Linear PPS is formed on polymerization because of the high electron density of the carbon in the para position. The ratios of the frontier electron density of the carbon in the para position on the disulfide to the sulfur atom are ordered as follows; 3,5‐dimethyl‐PS>2,5‐dimethyl‐PS‐3‐methyl‐PS>nonsubstituted PS>2‐methyl‐PS>2,6‐dimethyl‐PS. The formation energies of the σ‐complex, which is the intermediate of the reaction, also shows the same order. The theoretical calculation indicates that 3,5‐dimethyl disubstituted disulfide and 3‐methyl one are most preferable monomers of this cationic oxidative polymerization.
Study of the carbon fiber–Poly(Ether–Ether–Ketone) (PEEK) interfaces, 4: influence of fiber–matrix adhesion on the mechanical properties of unidirectional composites
Authors: Nardin M. , Asloun E. M. , Schultz J. , Brandt J. , Richter H.
Published: April 2003

The aim of the last part of this general study is to analyze the influence of the interfacial properties and, more precisely, the adhesion energy, between carbon fibers and PEEK on the final performance of unidirectional composites. A set of mechanical properties, i.e. interlaminar shear strength, longitudinal tensile and compressive and transverse tensile properties, of different unidirectional laminates with the same content (60% by volume) of carbon fibers is determined. It is first shown that the interlaminar shear strength is constant, whatever the type of materials. Therefore, this test is not appropriate to characterize the strength of the fiber–matrix interface in PEEK‐based composites. On the contrary, in agreement with previous work on other systems, it appears that the ultimate properties (longitudinal tensile and compressive as well as transverse tensile strengths and strains) of the laminates increase with the interfacial adhesion energy, whereas the stiffness of these composites remains unaffected in all cases.
Temperature diffusivity and heat conductivity of Langmuir–Blodgett–Kuhn and thin spun‐on polymer films
Authors: Fischer Thomas M. , Knoll Wolfgang
Published: April 2003

The temperature diffusivity β and heat conductivity κ of thin polymer films were measured at room temperature. Temperature waves were excited at one side of the film and detected at the other side with a pyroelectric foil (PVDF). The dependence of β and κ on chemical and structural parameters have been studied. For the first time, Langmuir–Blodgett–Kuhn multilayer assemblies prepared from “hairy rod” polymers were characterized: μm thin films of stiff polyamides prepared by spincoating exhibit heat conductivities an order of magnitude larger than “classical” polymers.
Adsorption of anti‐human IgG to plasma‐polymerized allylamine film formed on a silver plate
Authors: Kurosawa Shigeru , Kamo Naoki , Muratsugu Makoto
Published: April 2003

Increase in the sensitivity of an immunosensor or biosensor requires the immobilization of a large amount of proteins. Good materials must be developed for this protein adsorption. Allylamine thin film was formed on a flat silver plate by plasma polymerization; this plate is referred to as Ag(ALAM). Ag(ALAM) films were characterized by SEM, FT–IR and ESCA. Investigations on adsorption and desorption of F(ab')2 anti‐human IgG (hIgG) on to Ag and Ag(ALAM) revealed the following: (1) The adsorption isotherm of F(ab')2 anti‐hIgG on to AG(ALAM) or Ag was of a Langmuir type. The binding constant (Kb) and saturation binding (Ab) for this protein on to Ag(ALAM) were 8.93 l/mol and 181.8 nmol/m2, respectively, and for Ag, were 7.71 l/mole and 87.9 nmol/m2. (2) The extent of desorption of labeled F(ab')2 anti‐hIgG absorbed on the two plates was the same. (3) Ag(ALAM) and Ag were used as solid phases in a two‐site immunoradiometric assay of human serum IgG. The dose‐response on AG(ALAM) occurred at lower concentration, and was of greater magnitude than that on Ag.
Kinetics of swelling of polyacrylamide gels: concentration profiles and effect of an imposed strain
Authors: Peters Arsène , Hocquart Roger , Candau Sauveur J.
Published: April 2003

The time course of the concentration profile of a spherical gel has been measured during a swelling experiment, and compared to the theoretical expressions. The swelling of a cylindrical gel under imposed strain has been studied both theoretically and experimentally. This provides a new method of determination of the ratio of the shear modulus over the osmotic longitudinal modulus.