bluuebunny/crossref_metadata_2025 huggingface dataset:
Double locus analysis of chromosome 21 for preimplantation genetic diagnosis of aneuploidy
Authors: Magli M. C. , Sandalinas M. , Escudero T. , Morrison L. , Ferraretti A. P. , Gianaroli L. , Munné S.
Published: August 2002

Preimplantation genetic diagnosis (PGD) of numerical chromosome abnormalities significantly reduces spontaneous abortions and may increase pregnancy rates in women of advanced maternal age undergoing in vitro fertilization. However, the technique has an error rate of around 10% and trisomy 21 conceptions have occurred after PGD. To further reduce the risk of transferring trisomy 21 embryos to the patient, we designed a protocol that analyzes chromosome 21 twice by targeting two different loci. This protocol was applied to 388 embryos from 60 cycles of PGD of aneuploidy. The scoring criterion used was based on giving equal importance to both probe results. Of the 242 embryos diagnosed as abnormal, 125 were re‐biopsied to assess the rate of false positives and false negatives of the protocol and their clinical relevance.

The results of the present study showed no reduction in the overall fluorescent in situ hybridization (FISH) error rate for single cells. However, by using a different scoring criterion, the incidence of false negative can be reduced to 1.6% without missing any trisomy 21. In addition, the present study suggests that if two or more loci from the same chromosome could be simultaneously analyzed in single cells, errors caused by false monosomies could be reduced. Copyright © 2001 John Wiley & Sons, Ltd.
Ultrasound in prenatal diagnosis: polemics around routine ultrasound screening for second trimester fetal malformations
Authors: Levi Salvator
Published: August 2002

Ultrasound for routine fetal malformation screening has been polemical from its early beginning because of the very broad range of diagnosis rates disclosed, i.e. from 13% to 82%, average 27.5%. A review of available studies is proposed to assess objectively the efficacy of ultrasound, considering also economical, ethical and methodological aspects as influential factors for choosing a routine screening policy. The utility of fetal malformation diagnosis before birth is brought forward, including second opinion, karyotyping, poly‐disciplinary case discussion prior to management. Method and material of reviewed studies considerably vary and might influence the sensitivity results, as the choice of the population sample and selection of pregnant women, gestation age at screening, distribution of malformation among systems or tracts, exclusion of some fetal malformation and the routine practice of autopsy. Efficiency of screening studies is compared, and among them Radius and Eurofetus studies. Average sensitivity is finally considered as satisfactory in the daily practice when operated by trained personnel. The importance of additional factors for successful screening are emphasized such as education, equipment quality and fetal ultrasound examination at different gestation age for a better understanding of natural history of fetal morphology. Copyright © 2002 John Wiley & Sons, Ltd.
Prenatal diagnosis using interphase fluorescence in situ hybridization (FISH): 2‐year multi‐center retrospective study and review of the literature
Authors: Tepperberg J. , Pettenati M. J. , Rao P. N. , Lese C. M. , Rita D. , Wyandt H. , Gersen S. , White B. , Schoonmaker M. M.
Published: August 2002

Since 1993, the position of the American College of Medical Genetics (ACMG) has been that prenatal interphase fluorescence in situ hybridization (FISH) is investigational. In 1997, the FDA cleared the AneuVysion® assay (Vysis, Inc.) to enumerate chromosomes 13, 18, 21, X and Y for prenatal diagnosis. Data is presented from the clinical trial that led to regulatory clearance (1379 pregnancies) and from retrospective case review on 5197 new pregnancies. These studies demonstrated an extremely high concordance rate between FISH and standard cytogenetics (99.8%) for specific abnormalities that the AneuVysion assay is designed to detect. In 29 039 informative testing events (6576 new and 22 463 cases in the literature) only one false positive (false positive rate=0.003%) and seven false negative results (false negative rate=0.024%) occurred. A historical review of all known accounts of specimens tested is presented (29 039 using AneuVysion and 18 275 specimens tested with other probes). These performance characteristics support a prenatal management strategy that includes utilization of FISH for prenatal testing when a diagnosis of aneuploidy of chromosome 13, 18, 21, X or Y is highly suspected by virtue of maternal age, positive maternal serum biochemical screening or abnormal ultrasound findings. Copyright © 2001 John Wiley & Sons, Ltd.
Glucagon administration – underevaluated and undertaught
Authors: Harrism G. , Diment A. , Sulway M. , Wilkinson M.
Published: August 2002

Glucagon treatment requires a manually dexterous ‘operator’ who is composed, confident and competent in the whole procedure. Anecdotal reports from parents of teenagers describing difficulties in administering this procedure during severe hypoglycaemia led us to investigate the ‘techniques’ of 136 parents (106 parents of teenagers and 30 parents of young children). A simulated administration by parents using Novo Nordisk Glucagen® Hypokits was timed, rated and compared with a group of diabetes health professionals. Parent's ‘real life’ experiences of education and administration were obtained with a standard questionnaire. Glucagon residues in syringes and vials were estimated in a laboratory. Sixty nine per cent had handling difficulties ranging from opening the container to drawing the correct dose into the syringe. There was no statistical difference in time taken to complete the procedure between the two parent groups. However there was a significant difference between parents and the professional group. Parents were not accurate in administering dosages as recommended. Young children weighing more than 25 kg would have received less than the required dose. All parents reported verbal instruction with demonstration of the procedure at initial education. We suggest that glucagon administration needs to be taught ‘hands on’ and the skill reassessed on an annual basis. Copyright © 2001 John Wiley & Sons, Ltd.
Safety considerations for new vaccine development
Authors: Ellenberg Susan S.
Published: August 2002

Vaccines are highly effective and extremely safe. Although most known vaccine reactions are minor (e.g. fever, injection site pain or swelling), rare but serious reactions such as vaccine‐associated paralytic polio do occur. When large populations are vaccinated, some adverse health events may occur by chance shortly after vaccination. It is difficult to determine whether these are truly coincidental or attributable to the vaccine. The most reliable way to assess causality is in a controlled study, but clinical trials of new vaccines are typically too small to detect rare but serious effects. If the size of these trials were increased, much more could be learned about the safety of a vaccine prior to its exposure to entire populations. This information would increase confidence in the safety of vaccines, would be a valuable resource for assessing spontaneous reports of adverse events after licensure, and would reduce the risk of licensing a new vaccine that had the potential to cause severe injury to a small proportion of vaccinees. Published in 2001 by John Wiley & Sons, Ltd.
Copolymerization of ethylene with aromatic vinyl monomers using metallocenes
Authors: Kumar K Rajesh , Sivaram S
Published: August 2002

Copolymerization of ethylene with styrene, allyl benzene and 4‐phenyl‐1‐butene was examined using different metallocene catalysts. We separated the bulky phenyl group of styrene from its double bond using methylene spacers and studied the effect on its copolymerization behaviour with ethylene. The extent of incorporation of the comonomer is in the order 4‐phenyl‐1‐butene > allyl benzene > styrene for all catalysts. The comonomer incorporation was found to be less than 10 mol% under the experimental conditions employed in the present study.

© 2001 Society of Chemical Industry
Mechanical characteristics of poly(2‐hydroxyethyl methacrylate) hydrogels crosslinked with various difunctional compounds
Authors: Lou Xia , van Coppenhagen Claire
Published: August 2002

Poly(2‐hydroxyethyl methacrylate) hydrogels were prepared in the presence of 30 wt% water using two series of crosslinking agents including divinylic (ethyleneglycol dimethacrylate, 1,4‐butanediol dimethacrylate, 2,3‐dihydroxybutanediol 1,4‐dimethacrylate) and diallylic (1,5‐hexadiene‐3,4‐diol and 1,5‐hexadiene) compounds, over a concentration range between 0.1 and 5 mol%. The resulting polymers were swollen in water to yield homogeneous transparent hydrogels. These hydrogels were characterised in terms of equilibrium swelling in water, tensile properties and compression stress–strain measurements. The influences of the nature and the concentration of crosslinking agent on the swelling behaviour and the mechanical properties of these hydrogels were investigated. The crosslinking efficiency of two representative agents (ethyleneglycol dimethacrylate and 1,5‐hexadiene‐3,4‐diol) was quantified by compression experiments. A much lower crosslinking efficiency (0.013) was observed for 1,5‐hexadiene‐3,4‐diol than for ethyleneglycol dimethacrylate (0.336). It is suggested that the low crosslinking efficiency of diallylic agents is responsible for a trend in properties different from that displayed by the gels crosslinked with dimethacrylates. A comparison was made to the similar effect observed previously in heterogeneous PHEMA hydrogels.

© 2001 Society of Chemical Industry
Aqueous polymerization of ethyl acrylate initiated by ceric ion‐reducing agent systems in nitric acid medium
Authors: Reddy G V Ramana , Muthulakshmi A , Evangelin C Dulcy , Rajendran P
Published: August 2002

Kinetic study of aqueous polymerization of ethyl acrylate (EA) was carried out at 30 °C in dilute nitric acid medium by employing ammonium ceric nitrate (ACN)–methyl cellosolve (MC) and ACN–ethyl cellosolve (EC) as redox initiator systems. The ceric ion consumption was found to be first order with respect to ceric ion concentration with both initiator systems. The formation of complexes between Ce(IV) and reducing agents (RA) was observed. The order with respect to Ce(IV), reducing agents and monomer was evaluated for aqueous polymerization of EA by Ce(IV)–MC and Ce(IV)–EC redox initiator systems. The overall activation energy, Eoverall, for aqueous polymerization of EA was evaluated in the temperature region of 27–40 °C with both initiator systems. A kinetic mechanism for aqueous polymerization of EA initiated by redox initiator systems is presented.

© 2001 Society of Chemical Industry
Counter‐ion‐specific helix formation of poly(γ‐methyl L‐glutamate) derivatives containing sulfonate group in aqueous alcohols
Authors: Ando Akihiro , Satoh Mitsuru
Published: August 2002

Charged polypeptides containing sulfonate groups were prepared by transesterification of poly(γ‐methyl L‐glutamate) with isethionic acid. The coil–helix transition of the sulfonated polypeptides was investigated in aqueous alcohols. Marked counter‐ion specificity was observed for helix formation: Li+ < Na+ < Cs+ ≦ Rb+ ≦ K+; this was different to that for poly(L‐glutamate) (PLG): Cs+ ≪ K+ < Li+ < Na+. Specific helix stabilization by counter‐ion mixing, which has been found for the PLG system, was not observed for the sulfonated polypeptides. The counter‐ion‐ and solvent‐specific helix formation is discussed and compared with that in PLG.

© 2001 Society of Chemical Industry
Influence of molecular interactions on spherulite morphology in miscible poly(ethylene oxide)/epoxy network versus poly(ethylene oxide)/poly(4‐vinyl phenol) blend
Authors: Huang Yin Ping , Kuo Jen‐Fen , Woo E M
Published: August 2002

Relationships between the spherulite morphology and changes in hydrogen‐bonding interactions between the linear poly(ethylene oxide) (PEO) polymer and a crosslinking epoxy system (diglycidylether of bisphenol‐A resin with 4,4′‐diaminodiphenylsulfone) (DGEBA/DDS) before and after cure have been explored The hydrogen‐bonding interaction is more significant before cure because of the interactions between the ether group of PEO and the amine group of DDS. The interaction between PEO and epoxy/DDS becomes less in the cured network. The morphology of the PEO crystals is, in turn, affected by the contents and chemical structures (functional groups, molecular weights, crosslinks, etc) of crosslinking epoxy/DDS. PEO/poly(4‐vinyl phenol) (PVPh), a thermoplastic non‐curing miscible system with the hydrogen bonding between the ether group of PEO and the OH group of PVPh, is also compared. In comparison with the PEO/epoxy/DDS system, the spherulite morphology of PEO/PVPh becomes more extensively spread out, with the extents increasing with the PVPh contents in the PEO/PVPh blend.

© 2001 Society of Chemical Industry
Effect of multifunctional comonomers on the properties of poly(ethylene terephthalate) copolymers
Authors: Yoon Kwan Han , Min Byung Ghyl , Park O Ok
Published: August 2002

The properties of poly(ethylene terephthalate) (PET) and its copolymers containing 0.04–0.15 mol% of pentaerythritol and trimethylolethane (TME) have been investigated. The molecular weight of the copolymers increased with comonomer content, and this effect was observed significantly with pentaerythritol copolymers, resulting in broad molecular weight distribution. The comonomer effect on the mechanical properties was small. The shear viscosity of the copolymers showed shear thinning within the experimental shear rate range. The crystallization rate and birefringence of the fibres containing 0.103 mol% pentaerythritol increased with the spin draw ratio, whereas they decreased with comonomer content.

© 2002 Society of Chemical Industry
Emotional/behavioral disabilities and gifted and talented behaviors: Paradoxical or semantic differences in characteristics?
Authors: Morrison William F.
Published: August 2002

The identification of gifted and talented behaviors within students who have an identified exceptionality has resulted in the questioning of traditional profiles of individuals qualifying for services within gifted and special education. Much of this reflection to date has been focused on the characteristics of gifted and talented behaviors exhibited by students with high incidence disabilities (learning disabilities and attention deficit/hyperactivity disorders). Absent from the literature has been an examination of the learning and personal characteristics of students identified as having an emotional/behavioral disability who concurrently exhibit gifted and talented behaviors. An exploration of the growing body of literature in the fields of gifted and special education has revealed a number of similar or common characteristics in these two populations that warrant investigation. The purpose of this article is to develop a profile in the aforementioned population to aid in the identification of, and programming for, individuals with an emotional/behavioral disability who exhibit gifted and talented behaviors. © 2001 John Wiley & Sons, Inc.
Polyether‐bridged cyclophanes incorporating bisphenol A units as neutral receptors for quats: synthesis, molecular structure and binding properties
Authors: Cort Antonella Dalla , Nissinen Maija , Mancinetti Daniele , Nicoletti Elena , Mandolini Luigi , Rissanen Kari
Published: August 2002

Two novel neutral polyoxyethylene bridged cyclophanes (2a and 2b) incorporating bisphenol A units were synthesized and characterized by means of x‐ray crystal structure determination. The binding properties of 2a and 2b toward tetramethylammonium, N‐methylpyridinium, and acetylcholine cations were evaluated by means of 1H NMR spectroscopy. Consistent with indications provided by the molecular structure, the cavity in the basket‐like cyclophanes is large enough to accommodate the given guest cations conveniently. Circumstantial evidence was obtained that 1,1,2,2‐tetrachloroethane is too large to enter the cavity of the smaller cyclophane 2a, but can be included in the cavity of the larger cyclophane 2b. Copyright © 2001 John Wiley & Sons, Ltd.
Synthesis and hydrogel formation of fluorine‐containing amphiphilic ABA triblock copolymers
Authors: Matsumoto Kozo , Nishimura Ryuji , Mazaki Hiroaki , Matsuoka Hideki , Yamaoka Hitoshi
Published: August 2002

Fluorine‐containing amphiphilic ABA triblock copolymers, poly(2‐hydroxyethyl vinyl ether)‐block‐poly[2‐(2,2,3,3,3‐pentafluoropropoxy)ethyl vinyl ether]‐block‐poly(2‐hydroxyethyl vinyl ether) [poly(HOVE‐b‐PFPOVE‐b‐HOVE)] (HFH), poly[2‐(2,2,3,3,3‐pentafluoropropoxy)ethyl vinyl ether]‐block‐poly(2‐hydroxyethyl vinyl ether)‐block‐poly[2‐(2,2,3,3,3‐pentafluoropropoxy)ethyl vinyl ether] [poly(PFPOVE‐b‐HOVE‐b‐PFPOVE)] (FHF), and poly(n‐butyl vinyl ether)‐block‐poly(2‐hydroxyethyl vinyl ether)‐block‐poly(n‐butyl vinyl ether) [poly(NBVE‐b‐HOVE‐b‐NBVE)] (LHL), were synthesized, and their behavior in water was investigated. The aforementioned polymers were prepared by sequential living cationic polymerization of 2‐acetoxyethyl vinyl ether (AcOVE) and PFPOVE or NBVE, followed by hydrolysis of acetyl groups in polyAcOVE. FHF and LHL formed a hydrogel in water, whereas HFH gave a homogeneous aqueous solution. In addition, the gel‐forming concentration of FHF was much lower than that of corresponding LHL. Surface‐tension measurements of the aqueous polymer solutions revealed that all the triblock copolymers synthesized formed micelles or aggregates above about 1.0 × 10−4 mol/L. The surface tensions of HFH and FHF solutions above the critical micelle concentration were lower than those of LHL, indicating high surface activity of fluorine‐containing triblock copolymers. Small‐angle X‐ray scattering measurements revealed that HFH formed a core‐shell sperical micelle in 1 wt % aqueous solutions, whereas the other block copolymers caused more conplicated assembly in the solutions. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3751–3760, 2001
Biodegradation of copolymers composed of optically active L‐lactide and (R)‐ or (S)‐1‐methyltrimethylene carbonate
Authors: Tsutsumi Chikara , Yasuda Hajime
Published: August 2002

Random copolymerizations of L‐lactide with (R)‐, (S)‐, or rac‐1‐methyltrimethylene carbonate with bis(pentamethylcyclopentadienyl) samarium‐methyl tetrahydrofuranate [(C5Me5)2SmMe(THF)] as a novel initiator provided high molecular weight polymers with low polydispersities. Biodegradation of the resulting polymers with tricine and {N‐[tris(hydroxymethyl)methyl]‐2‐aminoethane sulfonic acid (TES) buffers as well as activated sludge showed only a small weight loss, whereas the polymer with proteinase K revealed high biodegradability independent of the optical activity of 1‐methyltrimethylene carbonate. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3916–3927, 2001
Atom transfer radical copolymerization of N‐phenylmaleimide and styrene initiated with dendritic polyarylether 2‐bromoisobutyrate
Authors: Zhao You‐Liang , Jiang Jing , Liu Hong‐Wei , Chen Chuan‐Fu , Xi Fu
Published: August 2002

Dendritic polyarylether 2‐bromoisobutyrates with different generations (Gn‐Br, n = 1–3) were prepared by reaction of the Fréchet‐type hydroxyl‐terminated polyarylether with 2‐bromoisobutyryl bromide and triethylamine. Gn‐Br as a macroinitiator for the controlled free‐radical polymerization of N‐phenylmaleimide (PhMI, M1) and styrene (St, M2) was investigated. The copolymerization carried out in anisole with CuBr/bpy catalyst afforded polymers with well‐defined molecular weights and low polydispersities (1.12 < Mw/Mn < 1.35). When the molar fraction of PhMI was 0.50, the apparent activation enthalpy of copolymerization was 38.2 kJ/mol. The effects of monomer feed on the apparent activation enthalpy and copolymer composition were also studied. The monomer reactivity ratios were determined to be r1 = 0.0325 and r2 = 0.0524 according to the Kelen–Tüdős method. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3960–3966, 2001
Physicochemical and thermal studies of viscose rayon borate fiber and its carbon fiber
Authors: Ko Young Gun , Choi Ung Su , Ahn Dong June , Kim Jeong Su , Kim Tae Young
Published: August 2002

Nonhalogen compounds have been studied for improvements in the flameproofing property and toxicity of flame retardants. Borate compounds have properties of multifunctional smoke suppressants, flame retardants, and afterglow suppressants. In this study, borate was coupled onto the surface of viscose rayon felt. Coupling and carbonization were confirmed by attenuated total reflectance Fourier transform infrared (ATR FTIR). The initial carbonization temperature was certified with ATR FTIR, elemental analysis of carbon, and thermogravimetric analysis. In the carbonization step, all chemical groups of the surface of the viscose rayon felt degraded to the various gases. Moreover, the weight percentage of the carbon element increased with increasing carbonization temperature. Initial rapid thermal degradation temperatures of viscose rayon prepared at various temperatures increased with the increasing reaction temperature. The activation energy was calculated with the Freeman and Carroll method. The activation energy of borate‐coupled viscose rayon decreased much more than before coupling. However, the activation energy increased with the increasing carbonization temperature in the carbonization step. Viscose rayon borates showed higher limiting oxygen index (LOI) values and volumetric resistance rate values than viscose rayon phosphates. In this article, the relationship between the activation energy and LOI is studied. The synthesized viscose rayon borate is found to be highly effective as a flame retardant and electrically resistant. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3875–3883, 2001
Lanthanocene amide complexes as single‐component initiators for the polymerization of (dimethylamino)ethyl methacrylate
Authors: Shen Qi , Wang Yaorong , Zhang Keda , Yao Yingming
Published: August 2002

Polymerization of (dimethylamino)ethyl methacrylate (DMAEMA) by lanthanocene amide complexes was investigated. The results show that (MeC5H4)2LnN(i‐Pr)2[tetrahydrofuran (THF)] (Ln = Y, Er, Yb), (MeC5H4)2YbNC5H10(HNC5H10) (HNC5H10 = piperidine), (MeC5H4)2YbNPh2(THF), and (t‐BuC5H4)2YbNPh2(THF) are effective initiators for the polymerization of DMAEMA, and the molecular weights of the polymers obtained exceed 100 × 103. The polymerization reactions can be varied over quite a broad range of temperatures from −78 to 40 °C. The central metals and amido groups had a significant effect on the polymerization activity. The increasing activity of central metals and amido groups was Yb < Er < Y and NPh2 < N(i‐Pr)2 < NC5H10, respectively. © 2002 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 612–616, 2002; DOI 10.1002/pola.10141
Synthesis of star‐shaped copolymers with methyl methacrylate and n‐butyl methacrylate by metal‐catalyzed living radical polymerization: Block and random copolymer arms and microgel cores
Authors: Baek Kyung‐Youl , Kamigaito Masami , Sawamoto Mitsuo
Published: August 2002

Various star‐shaped copolymers of methyl methacrylate (MMA) and n‐butyl methacrylate (nBMA) were synthesized in one pot with RuCl2(PPh3)3‐catalyzed living radical polymerization and subsequent polymer linking reactions with divinyl compounds. Sequential living radical polymerization of nBMA and MMA in that order and vice versa, followed by linking reactions of the living block copolymers with appropriate divinyl compounds, afforded star block copolymers consisting of AB‐ or BA‐type block copolymer arms with controlled lengths and comonomer compositions in high yields (≥90%). The lengths and compositions of each unit varied with the amount of each monomer feed. Star copolymers with random copolymer arms were prepared by the living radical random copolymerization of MMA and nBMA followed by linking reactions. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 633–641, 2002; DOI 10.1002/pola.10145
Synthesis of novel nitrogen‐ and sulfur‐containing conjugated polymers used as hole‐transporting materials for organic light‐emitting diodes
Authors: Zhu Kaizheng , Xie Zhiyuan , Wang Lixiang , Jing Xiabin , Wang Fosong
Published: August 2002

Two series of highly soluble novel nitrogen‐ and sulfur‐containing conjugated polymers were synthesized via an acid‐induced self‐polycondensation of functional monomers with methyl sulfinyl and aromatic groups. The well‐defined structures of synthesized polymers were confirmed by their NMR and IR spectra. The highest occupied molecular orbital energy values for these materials, estimated by cyclic voltammetry, showed a broad range of values from about 5.0 to 5.2 eV used as hole‐transport layers (HTL) in two‐layer light‐emitting diodes ITO/HTL/Alq3/Mg:Ag [ITO = indium tin oxide, and Alq3 = tris(8‐quinolinato) aluminum]. The typical turn‐on voltage of these diodes was about 4–5 V. The maximum brightness of the device was about 3440 cd/m2 at 20 V. The maximum efficiency was estimated to be 0.15 lm/W at 10 V. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1321–1333, 2002
Functionalization of polyethylene with silane comonomers
Authors: Lipponen S. , Seppälä J.
Published: August 2002

We synthesized a new weakly interacting monomer with a reactive phenylsilane group that is an intermediate for many functional groups. The synthesis was performed in two steps: the hydrosilylation of 1,7‐octadiene with dimethylchlorosilane and a Grignard reaction with phenyl magnesium bromide. The new monomer, 7‐octenyldimethylphenylsilane, was isolated and copolymerized with ethylene via metallocene catalysts (Me2Si(Me‐2‐Ind)2ZrCl2 and Et(Ind)2ZrCl2) and methylaluminoxane (MAO) as a cocatalyst. Electropositive silicon had no negative effect on the copolymerization reaction. The polymerization activity increased, and the molar mass of the product remained at a high level. The comonomer incorporation reached a significant 11.8 wt % (2.6 mol %). © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1303–1308, 2002
Styrylpyridinium borate salts as dye photoinitiators of free‐radical polymerization
Authors: Jędrzejewska Beata , Kabatc Janina , Pietrzak Marek , Pączkowski Jerzy
Published: August 2002

Styrylpyridinium borate salts photoinitiate free‐radical polymerization. The rate of photopolymerization depends on the ΔGo of electron transfer between a borate anion and a styrypyridinium cation. This latter value was estimated for a series of styrylpyridinium borate salts, and the relationship between the rate of polymerization and the free energy of activation gives the dependence predicted by the classical theory of electron transfer. This relation was independently observed for the two series of styrylpyridinium borate salts tested—one for the photoredox pair with an iodine atom and the second without. Styrylpyridinium borate salts were stable at ambient temperature in the formulations prepared for the photopolymerization experiments. Photopolymerization initiated by the photoredox pairs tested proceeded by the conventional mechanism in which bimolecular termination occurs by a reaction between two macroradicals. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1433–1440, 2002
Kinetics of alpha‐methylstyrene oligomerization by catalytic chain transfer
Authors: Gridnev A. A.
Published: August 2002

Alpha‐methylstyrene (AMS) can be effectively dimerized by a free‐radical mechanism mediated by the catalytic chain transfer (CCT). Above the ceiling temperature of AMS, 61 °C, the dimer may become almost an exclusive product with only a small percentage of impurity of AMS trimer and tetramer. Kinetics of the AMS oligomerization has two characteristic features. First, the rate of the oligomerization increases with concentration of the CCT catalyst. Second, conversion reaches a plateau at 60–70%. A kinetic scheme explained both effects. Besides AMS, para‐ and methasubstituted AMS can also be dimerized. Orthosubstituted AMS's do not oligomerize. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1366–1376, 2002
Fluoride‐terminated hyperbranched poly(arylene ether phosphine oxide)s via nucleophilic aromatic substitution
Authors: Bernal David P. , Bankey Nathaniel , Cockayne Robert C. , Fossum Eric
Published: August 2002

A series of ABx‐type triarylphosphine oxide monomers, bis‐(4‐fluorophenyl)‐(4‐hydroxyphenyl)phosphine oxide (4a), bis‐(3,4‐difluorophenyl)‐(4‐hydroxyphenyl)phosphine oxide (4b), and 4‐hydroxyphenyl‐bis‐(3,4,5‐trifluorophenyl)phosphine oxide (4c) were prepared, characterized, and polymerized under nucleophilic aromatic substitution conditions [N‐methylpyrrolidone (NMP), K2CO3] to provide the corresponding hyperbranched poly(arylene ether phosphine oxide)s with number‐average molecular weights ranging from 9200 to 14,600 Da. NMR spectroscopic analysis indicated the presence of highly branched products with an approximate degree of branching of 0.57. The polymers were soluble in a variety of typical organic solvents and displayed excellent thermal stability. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1456–1467, 2002
Cationic ring‐opening polymerization of monothiocarbonate with a norbornene group
Authors: Nemoto Nobukatsu , Kakimoto Keiichiro , Endo Takeshi
Published: August 2002

This work deals with the cationic ring‐opening polymerization of cyclic thiocarbonates with a norbornene or norbornane moiety, that is, 5,5‐(bicyclo[2.2.1]hept‐2‐ene‐5,5‐ylidene)‐1,3‐dioxane‐2‐thione (TC1) or 5,5‐(bicyclo[2.2.1]heptane‐5,5‐ylidene)‐1,3‐dioxane‐2‐thione (TC2), respectively. The reaction of TC1 initiated by trifluoromethanesulfonic acid (TfOH), methyl trifluoromethanesulfonate (TfOMe), boron trifluoride etherate (BF3OEt2), or triethyloxonium tetrafluoroborate (Et3OBF4) afforded unidentified products; however, TC1 underwent cationic ring‐opening polymerization with methyl iodide as an initiator to afford polythiocarbonate because the propagating end was stabilized by the covalent‐bonding property. The polymerization of TC2 initiated by TfOH, TfOMe, BF3OEt2, or Et3OBF4 afforded polythiocarbonate with good solubility in common organic solvents and a narrow molecular weight distribution because of the absence of a double‐bond moiety. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1698–1705, 2002
Synthesis and properties of novel polyurethanes containing 3,4‐dioxybenzylidenecyanoacetate group as a nonlinear optical chromophore
Authors: Lee Ju‐Yeon , Park Eun‐Ju
Published: August 2002

Methyl 3,4‐di‐(2′‐hydroxyethoxy)benzylidenecyanoacetate (3) was prepared by hydrolysis of methyl 3,4‐di‐(2′‐vinyloxyethoxy)benzylidenecyanoacetate (2). Diol 3 was condensed with 2,4‐toluenediisocyanate, 3,3′‐dimethoxy‐4,4′‐biphenylenediisocyanate, and 1,6‐hexamethylenediisocyanate to yield polyurethanes 4–6 containing the nonlinear optical chromophore 3,4‐dioxybenzylidenecyanoacetate. The resulting polyurethanes 4–6 were soluble in common organic solvents such as acetone and dimethylformamide. Polymers 4–6 indicated thermal stability up to 300 °C in thermogravimetric thermograms with glass‐transition temperature values obtained from differential scanning calorimetric thermograms in the range of 78–102 °C. The second‐harmonic generation coefficients (d33) of the poled polymer films were around 6.9 × 10−9 esu. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1742–1748, 2002
Preparation of the thermotropic copoly(amide ester) of p‐aminobenzoic acid and m‐hydroxybenzoic acid with diphenyl chlorophosphate/pyridine
Authors: Higashi Fukuji , Komatsu Masao , Takizawa Junko
Published: August 2002

A thermotropic copoly(amide ester) exhibiting a nematic mesophase within the range of 240–360 °C was prepared by the solution copolycondensation of p‐aminobenzoic acid (40–70 mol %) and m‐hydroxybenzoic acid with diphenyl chlorophosphate in pyridine in the presence of LiCl. For control of the sequence distribution of p‐aminobenzoic acid, the amount of LiCl and the dropwise addition of the phosphate were examined. The transition temperatures (from a solid phase to a nematic mesophase) of the resultant copolymers were affected by the period of addition and the amounts of the aminobenzoic acid and LiCl and were investigated in terms of the distributions of the monomers determined by 1H NMR. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1775–1780, 2002
An efficient route for the synthesis of hyperbranched polymers and dendritic building blocks based on urea linkages
Authors: Ambade Ashootosh V. , Kumar Anil
Published: August 2002

A highly efficient synthetic route, based on the quantitative reaction between amine and isocyanate functionalities, was used successfully for the synthesis of hyperbranched polymers and dendritic building blocks based on urea linkages. The thermal decomposition of 3,5‐diamino benzoyl azide or 5‐amino isophthaloyl azide generated in situ the corresponding phenyl isocyanates, which were then polymerized to give wholly aromatic hyperbranched polyureas. Hyperbranched polyurea with amine chain ends was soluble in common organic solvents. The degree of branching, as calculated with 1H NMR, was 0.55. Diethyl 5‐amino isophthalate and Boc‐protected 5‐amino isophthaloyl azide were used for the successful stepwise synthesis of dendritic wedges based on urea linkages. The thermal generation of the isocyanate functionality with gaseous nitrogen as the side product and its quantitative reaction with amine groups were the salient features of this convergent synthesis. This eliminated the use of chromatographic purification, an inherent part of other convergent growth approaches, and made it a very efficient synthetic route for the synthesis of dendritic wedges. The products were characterized by 1H NMR, 13C NMR, and electron spray mass spectroscopy (ESMS) techniques. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1295–1304, 2001
A novel route to poly(α‐hydroxyacrylic acid) derivatives by the hydrolysis of polymers containing 1,3‐dioxolan‐4‐one moiety
Authors: Miyagawa Toyoharu , Sanda Fumio , Endo Takeshi
Published: August 2002

The alkali hydrolysis of poly(2,2‐dimethyl‐5‐methylene‐1,3‐dioxolan‐4‐one) and poly(2,2‐dimethyl‐5‐methylene‐1,3‐dioxolan‐4‐one‐co‐styrene) was carried out with a sodium hydroxide solution (40%) in tetrahydrofuran at room temperature to obtain poly(α‐hydroxyacrylic acid) or poly(α‐hydroxyacrylic acid‐co‐styrene) with number‐average molecular weights of 39,000–73,000 in 41–86% yields. The styrene unit in the hydrolyzed copolymer hindered the formation of a lactone ring. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1629–1633, 2001
Promoted random orientation of the phenyl substituent of phenylhydroquinone–terephthalic acid polyesters prepared with a diphenyl chlorophosphate/pyridine condensing agent
Authors: Higashi Fukuji , Watabiki Mamoru , Kim Ji‐Hong
Published: August 2002

The reaction of sterically hindered hydroxyl groups at the 2‐position of methylhydroquinone and phenylhydroquinone (PhHQ) to form esters was largely promoted by their slow addition to benzoic acid activated by diphenyl chlorophosphate in pyridine. A modification of this reaction was applied to the preparation of thermotropic terephthalic acid/PhHQ and 2,5‐dichloroterephthalic acid/PhHQ polymers with randomly oriented phenyl substituents, and the properties of the polymers were studied in terms of their transition temperatures, which were determined by differential scanning calorimetry and microscopic observation. The melting points were lowered by about 30–50 °C by the dropwise addition of PhHQ over 10–30 min. The molecular structures of the 2,5‐dichloroterephthalic acid/PhHQ polymers were studied by 13C NMR. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1726–1732, 2001
Tertiary amine‐functionalized polymers by atom transfer radical polymerization
Authors: Summers Gabriel J. , Ndawuni M. Patrick , Summers Carol A.
Published: August 2002

The quantitative synthesis of tertiary amine‐functionalized polymers by atom transfer radical polymerization is reported. Tertiary amine‐functionalized polystyrene was prepared with the adduct of 1‐(bromoethyl)benzene with 1‐(4‐dimethyl‐aminophenyl)‐1‐phenylethylene as an initiator in the atom transfer radical polymerization of styrene in the presence of a copper (I) bromide/2,2′‐bipyridyl catalyst system. The polymerization proceeded via a controlled free‐radical polymerization process to afford quantitative yields of the corresponding tertiary amine‐functionalized polystyrene with predictable number‐average molecular weights (1600–4400), narrow molecular weight distributions (1.09–1.31), and an initiator efficiency of 0.95. The polymerization process was monitored by gas chromatographic analysis. The tertiary amine‐functionalized polymers were characterized by thin‐layer chromatography, size exclusion chromatography, potentiometry, and spectroscopy. All experimental evidence was consistent with quantitative functionalization via the 1,1‐diphenylethylene derivative. Polymerization kinetic measurements showed that the polymerization reaction followed first‐order‐rate kinetics with respect to monomer consumption and that the number‐average molecular weight increased linearly with monomer conversion. © 2001 John Wiley & Sons, Inc. J Polym Sci A Part A: Polym Chem 39: 2058–2067, 2001
Effect of pressure on the luminescence of a series of methoxy phenylacetylene dendrimers neat and in dilute solution in solid poly(tert‐butyl methacrylate)
Authors: Zhu A. , Bharathi P. , Drickamer H. G. , Moore J. S.
Published: August 2002

The effect of pressure up to 60 kbar was measured on the luminescence peak location and efficiency for a series of methoxy phenylacetylene dendrimers (MeO). Dendrimers MeO‐3, MeO‐7, MeO‐15, MeO‐31, MeO‐63, and MeO‐127 were studied as neat polymers. MeO‐3, MeO‐15, MeO‐63, and MeO‐127 were also investigated in dilute solutions in poly(tert‐butyl methacrylate). According to measurements of the dilute solutions, there is a charge‐transfer (CT) state that, for the smaller dendrimers, lies well above the π* state; for the larger dendrimers, it is the emitting state at 1 atm. With increasing pressure, the intramolecular CT state is rapidly stabilized, so that at high pressure the emission is from this state for all dendrimers. For the neat polymers, there is an initial redshift that reverses direction at a pressure that is higher for smaller dendrimers. This reversal is attributed to intermolecular CT. There may be changes in the molecular geometry and/or relative orientation of adjacent dendrimers that tend to stabilize the intermolecular CT in the solid state. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2859–2865, 2001
Chain‐extended, hydroxyterminated‐polybutadiene‐based polyurethaneureas: Synthesis, reaction kinetics, and properties
Authors: Gupta Tarakranjan , Adhikari Basudam
Published: August 2002

Hydroxyterminated‐polybutadiene‐based prepolyurethanes were prepared with two different catalysts, dibutyltindilaurate (DBTDL) and triethylamine (TEA); chain extension of the prepolyurethanes followed with two different aromatic diamines, oxydianiline and 4,4′‐diaminodiphenylsulfone, in various concentrations. The prepolyurethane synthesis followed second‐order kinetics, with the DBTDL catalyst showing better efficiency for urethane formation than TEA. TEA‐catalyzed synthesis suffered from the self‐association of isocyanates as a major side reaction, following second‐order kinetics with respect to isocyanate concentration. Although there was a gradual increase in the intrinsic viscosity during prepolyurethane synthesis in the presence of DBTDL, the intrinsic viscosity remained almost constant with the progress of the reaction in the presence of TEA. The tensile properties of prepolyurethane and polyurethaneureas synthesized in DBTDL‐catalyzed reactions were higher than the properties of those synthesized in TEA‐catalyzed reactions. The variation of the tensile strength with the diamine concentration was correlated with the crosslink density and sol fraction. The solubility of the hard segment of polyurethaneurea in the reaction medium appeared to be important in influencing the tensile properties. The effects of the diamine concentration (chain extender) on the diffusion coefficient and activation energy of diffusion of toluene in polyurethaneureas were studied. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2978–2992, 2001
Synthesis of a new polymer surface bearing grafted azo polymer chains
Authors: Poncin‐Epaillard Fabienne , Beunet Johann , Bulou A. , Bardeau Jean‐François
Published: August 2002

Azobenzene, a photosensitive chromophore that undergoes photoinduced and thermal cis–trans isomerization, can be applied in a nonlinear optical field. {4′‐[(Hydroxy)ethyl]amino}‐4‐nitroazobenzene (disperse red 1) corresponds to one of these azo compounds, which can be grafted to a polymer chain as a part of the main chain, as a dangling group, or onto the polymer surface. In the last case, disperse red 1 is transformed into an acrylic monomer and then grafted onto a polypropylene surface modified with a cold carbon dioxide‐plasma treatment. A method is proposed for quantifying the radicals formed during the plasma treatment and, consequently, for optimizing the grafting reaction. The best conditions (the nature of the solvent, temperature, monomer concentration, and duration) are given. Both IR and Raman spectroscopies were used as efficient techniques for grafting characterization. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3052–3061, 2001
Phase behavior of low molecular weight polyethylenes from homogeneous and heterogeneous solutions
Authors: Chatterjee Jhunu , Alamo Rufina G.
Published: August 2002

The pseudophase diagrams of solutions of low molecular weight polyethylene (PE) (number‐average molecular weight < 1500 g/mol) in octamethyl cyclotetrasiloxane (OCTS) and isododecane (IS) were determined by direct observation of cloud points and optical microscopy. In addition, melting temperatures were also determined by differential scanning calorimetry. In the range of single liquid–solid transitions, the data conformed to the classical melting temperature composition relation as a result of the formation of extended crystallites. The melting data were used to determine the interaction parameter of the PE in OCTS (1.4 ± 0.1) and IS (0.22 ± 0.05). The structural and thermal properties of the gels formed by a competing liquid–liquid and liquid–solid phase separation, under nonequilibrium conditions, contrast with the properties of the crystals formed from a single liquid–solid transition. Coarsening within the liquid phases was evidenced by optical microscopy, and insights about the mechanism of the kinetics of the coarsening process are given. The temporal changes of the melting temperature of crystallites formed from the heterogeneous phase (OCTS) reveal dynamics within a nonequilibrium state. In contrast, the crystallites formed from a homogeneous solution (IS) showed negligible melting‐temperature changes with time. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 878–889, 2002
Sphere‐to‐cylinder transition in dilute solutions of diblock copolymers
Authors: Termonia Yves
Published: August 2002

AB diblock copolymers dissolved in a selective solvent for block B spontaneously self‐assemble into spherical or cylindrical micelles with an A core surrounded by a corona of the B block. Using a Monte Carlo lattice model, we find that the sphere‐to‐cylinder transition can be fully described in terms of a packing parameter that depends on the relative cross sections of the two blocks. The latter can be varied either by a block length being changed or by the B block being allowed to adopt an ordered conformation (e.g., helical). The model results are in good agreement with experimental observation. They also shed some light onto the molecular origins of the ease of processing and exceptional mechanical properties of spider dragline. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 890–895, 2002
Unified analysis of thermodynamic and rheological properties of high polymer solutions. II. Ternary systems
Authors: Irurzun Isabel M. , Grigera Tomás S. , Cortizo M. Susana , Figini Rubén V. , Marx‐Figini Marianne
Published: August 2002

We extend to ternary solutions our previous study of conformational, thermodynamic, and rheological properties of semidilute polymer solutions in good solvent. Osmotic pressure and viscosity measurements were performed in several mixtures of two compatible polymers in a common solvent. Renormalization group results were used to analyze the data, using de Gennes's blobs model to connect dynamic and conformational properties. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1071–1079, 2002
Revisiting some phenomena in polyelectrolyte solutions
Authors: Morawetz Herbert
Published: August 2002

This review deals with the counterion distribution around rod‐shaped polyions, the reaction kinetics in polyelectrolyte solutions, the anomalous behavior of poly(methacrylic acid), and the formation of pearl‐necklace‐like structures of polyelectrolytes in poor solvent media. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1080–1086, 2002
Electrorheological properties of suspensions of monodispersed micron‐sized polyaniline composite particles
Authors: Jun Jung‐Bae , Lee Chung‐Hyuk , Kim Jin‐Woong , Suh Kyung‐Do
Published: August 2002

Monodispersed micron‐sized polyaniline (PANi) composite particles were synthesized by chemically oxidative polymerization of aniline in the presence of functional porous polymer particles. The formation of the PANi‐coated composite particles was confirmed by scanning electron microscopy. Electrorheological (ER) properties of the monosized composite particle suspensions were then investigated under different DC electric fields by altering the particle characteristics. The ER effect of the PANi composite suspensions was largely dependent on the composition ratio (PANi loading), the particle conductivity, and the particle concentration. Dynamic oscillation measurements revealed that the applied electric field induced the viscoelastic property of the ER suspensions by generating the chain structures of the suspended particles. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1163–1170, 2002
Temperature dependence of the phase separation in ethyl cyanoethyl cellulose/poly(acrylic acid)/4′‐n‐pentyl‐4‐cyano‐biphenyl composite films
Authors: Zhou Xuesong , Huang Yong
Published: August 2002

A novel polymer‐dispersed liquid‐crystal film consisting of micrometer‐scale liquid‐crystal droplets in ultraviolet‐cured polymer composite matrices with cholesteric order was prepared and the influence of cure temperature on the phase separation was studied. The existence and pitch of the ethyl cyanoethyl cellulose cholesteric liquid‐crystalline phase were influenced by the existence of low molecular weight liquid crystals. The macromolecular cholesteric phase disappeared when the 4′‐n‐pentyl‐4‐cyano‐biphenyl concentration was over 40 wt %, and 4′‐n‐pentyl‐4‐cyano‐biphenyl domains were dispersed in the isotropic matrix of the polymer composite. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1334–1341, 2002