bluuebunny/crossref_metadata_2025 huggingface dataset:
Biochemical screening for Down syndrome in pregnancies following renal transplantation
Authors: Karidas C. N. , Michailidis G. D. , Spencer K. , Economides D. L.
Published: August 2002

Objective

To assess the performance of the double marker test [free β‐human chorionic gonadotrophin (β‐hCG) and alpha‐fetoprotein (AFP)] as a screening test for Down syndrome in pregnant patients who had a prior renal transplant.

Design

A retrospective study.

Setting

The Fetal Medicine Unit, Royal Free Hospital, London, UK.

Methods

Detailed records of 14 post‐renal transplant pregnancies were obtained from the Renal Unit of our hospital where the patients were followed up. The serum concentrations of urea, creatinine, free β‐hCG and AFP at the time of the double marker test were recorded, with a cut‐off point of 1:250 for the double marker test. A control group of 14 normal pregnancies matched for age, parity and gestational age was used. The Mann‐Whitney U‐test and t‐tests of unequal variance were applied to compare parameters of the study and the control groups.

Results

Two patients in each group were high risk for Down syndrome and amniocentesis revealed normal karyotype. No babies with Down syndrome were delivered in either group. Regression analysis showed significant correlation between free β‐hCG and urea concentrations (p<0.001) and free β‐hCG and creatinine concentrations (p<0.001), but not for AFP.

Conclusions

The present study demonstrates that residual renal function alterations persisting after renal transplantation can affect the levels of free β‐hCG and AFP, thus resulting in false‐positive screening for Down syndrome. First trimester nuchal translucency (NT) measurement in combination with second trimester ultrasonographic markers can be used in these patients, or alternatively the free β‐hCG levels should be corrected according to the serum creatinine levels. Copyright © 2002 John Wiley & Sons, Ltd.
Systems for evaluation of new drugs in the United Kingdom
Authors: Beard Keith
Published: August 2002

The cost of drugs represents 10% of the National Health Service (NHS) budget in the UK and this fraction is increasing. Because the NHS is centrally funded and because there is a budgetary limit, prioritization in health care is required. The National Institute for Clinical Excellence in England and Wales and the Health Technology Board for Scotland have been established with the aim (among others) of ensuring that the NHS secures maximum health gain from available resources by focusing on treatments with clear evidence of cost effectiveness. Reconciling the interests of those responsible for financing the service with the interests of patients and other concerned parties might prove difficult. Copyright © 2001 John Wiley & Sons, Ltd.
Pharmacogenetics and pharmacoepidemiology
Authors: Jones Judith K.
Published: August 2002

This paper seeks to stimulate consideration of the short‐ and long‐term possibilities raised by research into pharmacogenetics and pharmacoepidemiology, to identify potential tissue databanks linked to population data, and to summarize our ethical responsibilities. Short term, we might identify selected disorders or risk factors, such as for drug‐associated serious events, and might find selected target populations. Long term, we might incorporate genomics techniques into population data and map genetic risk factors for diseases and drug responses. Tissue specimens that might be linked to clinical data lie in certain data resources: clinical trials, ad hoc cohorts, case registries, and cross‐sectional and longitudinal population samples. Specific areas must be addressed in research using human tissue and genetic material, including the ethical threat to privacy. We must avoid misuse of genetic information by breaching confidentiality and putting at risk specific genetically identifiable groups. The National Bioethics Advisory Commission recently addressed the issue of serum and tissue data banks in a published report summarized in this paper. Social, methodologic, and ethical issues relate to any protocol using serum and tissue, and indicate a need for broad educational efforts. We must set guidelines as pharmacogenetics research becomes a dimension of pharmacoepidemiology. Copyright © 2001 John Wiley & Sons, Ltd.
The use of anti‐asthmatic drugs in children: results of a community‐based survey in Germany
Authors: Beimfohr C. , Maziak W. , von Mutius E. , Hense H. W. , Leupold W. , Hirsch T. , Keil U. , Weiland S. K.
Published: August 2002

Purpose

To describe the use of anti‐asthma drugs in children in the general population and in children with asthma using data from two large surveys in Germany.

Methods

Community‐based random sample of 5–7 and 9–11‐year‐old children in Dresden and Munich were studied in 1995/96 by parental questionnaires using the Phase II protocol of the International Study of Asthma and Allergies in Childhood (ISAAC). A total of 11 094 children participated in the surveys (response rate 83%).

Results

In all children, inhaled β2‐agonists were used most frequently during the last 12 months (2.6%), followed by inhaled cromolyns (2.5%), oral β2‐agonists (1.5%), and inhaled steroids (0.9%). Drug use was significantly higher among boys than girls and in older children compared to younger ones (P < 0.05 for both). Among children with current asthma, 47% had used inhaled β2‐agonists, 43% inhaled cromolyns, 22% oral β2‐agonists, and 16% inhaled steroids. Inhaled steroids were used significantly more often in Dresden (21.7%) than in Munich (11.2%) (P < 0.05).

Conclusions

Among anti‐asthma drugs, agents used for symptomatic relief were the most frequently reported followed by inhaled anti‐inflammatory agents. Most of the anti‐inflammatory drugs used were SCG, which may indicate under‐treatment with inhaled steroids. Copyright © 2001 John Wiley & Sons, Ltd.
Impact of the Minimum Pricing Policy and introduction of brand (generic) substitution into the Pharmaceutical Benefits Scheme in Australia
Authors: McManus Peter , Birkett Donald J , Dudley John , Stevens Alan
Published: August 2002

Purpose

To describe the effects of introducing the Minimum Pricing Policy (MPP) and generic (brand) substitution in 1990 and 1994 respectively on the dispensing of Pharmaceutical Benefits Scheme (PBS) prescriptions both at the aggregate and individual patient level.

Methods

The relative proportion of prescriptions with a brand premium and those at benchmark was examined 4 years after introduction of the MPP and again 5 years later after generic substitution by pharmacists was permitted. To determine the impact of a price signal at the individual level, case studies involving a patient tracking methodology were conducted on two drugs (fluoxetine and ranitidine) that received a brand premium.

Results

From a zero base when the MPP was introduced in 1990, there were 5.4 million prescriptions (17%) dispensed for benchmark products 4 years later in 1994. At this stage generic (brand) substitution by pharmacists was then permitted and the market share of benchmark brands increased to 45% (25.2 million) by 1999. In the patient tracking studies, a significantly lower proportion of patients was still taking the premium brand of fluoxetine 3 months after the introduction of a price signal compared with patients taking paroxetine which did not have a generic competitor. This was also the case for the premium brand of ranitidine when compared to famotidine. The size of the price signal also had a marked effect on dispensing behaviour with the drug with the larger premium (fluoxetine) showing a significantly greater switch away from the premium brand to the benchmark product.

Conclusions

The introduction in 1990 of the Minimum Pricing Policy without allowing generic substitution had a relatively small impact on the selection of medicines within the Pharmaceutical Benefits Scheme. However the effect of generic substitution at the pharmacist level, which was introduced in December 1994, resulted in a marked increase in the percentage of eligible PBS items dispensed at benchmark. Case studies showed a larger premium resulted in a greater shift of patients from drugs with a brand premium to the benchmark alternative. Copyright © 2001 John Wiley & Sons, Ltd.
Using databases for studying and comparing health care costs and resource use
Authors: Melfi Catherine A.
Published: August 2002

Data sources such as medical insurance claims are increasingly used in health outcomes research. We present opportunities and limitations associated with the use of such data for conducting studies of health care costs and resource use. We also provide examples on using databases for conducting research when the primary objective is to study costs or resource use. This information is intended to be helpful to experienced health services researchers and to those new to the field of either outcomes research or cost effectiveness research. We examine the reasons for using databases to study costs and resource use, desirable attributes of databases used for this purpose, potential pitfalls, other issues associated with conducting cost and resource use studies with databases, and appropriate methods for this research. Through examples and references, we examine issues to be considered in each of these areas, and make recommendations. Strengths and limitations of databases are indicated. Research using claims data to determine health care cost and resource use should be carried out responsibly. Limitations must be acknowledged for research using databases, and appropriate methods must be used. Still, databases represent a rich opportunity to conduct research in health care costs and resource use, and much can be learned using databases. Copyright © 2001 John Wiley & Sons, Ltd.
Parenteral ketorolac and risk of myocardial infarction
Authors: Kimmel Stephen E. , Berlin Jesse A. , Kinman Judith L. , Hennessy Sean , Feldman Harold , Carson Jeffrey L. , Strom Brian L.
Published: August 2002

Purpose

To examine the effects of ketorolac, a non‐aspirin non‐steroidal anti‐inflammatory drug (NANSAID) with anti‐platelet properties, on the risk of in‐hospital myocardial infarction (MI).

Methods

A retrospective cohort study was performed among hospitalized patients given 10 219 courses of parenteral ketorolac and patients given 10 145 courses of parenteral opioids, without ketorolac, in 35 hospitals. Patients were matched by hospital, admitting service, and date of study drug initiation. Any MI documented in the chart that occurred during the drug course and up to 3 days after the last dose was recorded by trained abstractors.

Results

MI occurred in 18 (0.2%) ketorolac and 45 (0.4%) opioid courses (odds ratio (OR) 0.40, 95% confidence interval (CI) 0.23–0.69). This negative association persisted in multivariable analysis adjusting for age, sex, history of diabetes mellitus or cardiovascular disease, and administration of antiplatelet agents (OR 0.42; 95% CI 0.24–0.73). The association also persisted in numerous analyses excluding patients who may have been treated with analgesics for ischemic pain, and when restricting events to those occurring while on the drug (OR 0.34; 95% CI 0.17–0.69).

Conclusion

These results are consistent with a protective effect of ketorolac against MI. Future research that implements uniform screening for and independent validation of MIs as well as eliminates possible confounding by indication is the next logical step in confirming these findings. Copyright © 2002 John Wiley & Sons, Ltd.
Inappropriate prescriptions for the aging population of the United States: an analysis of the National Ambulatory Medical Care Survey, 1997
Authors: Huang Boji , Bachmann Kenneth A. , He Xuming , Chen Randi , McAllister Jennifer S. , Wang Tongtong
Published: August 2002

Purpose

Generally, elderly patients in the United States tend to consume more prescriptions than younger adults. The purpose of the study is to examine nationwide prescription patterns for elderly patients who visited physicians' offices in 1997.

Methods

The database of a nationwide sample survey of practicing physicians participating in the National Ambulatory Medical Care Survey, 1997 was used. Inappropriate medicines for the elderly were identified using previously published and widely accepted criteria.

Results

During 1997, patients aged 65 years or older made more than 191 million visits to physicians' offices in the United States. Four or more prescriptions per visit were issued with the following frequencies: 17.7% for females; 16.4% for males; 17.0% for Whites, 22.7% for Blacks, and 6.1% for other minorities including American Asians, Indians, Eskimos, Aleuts and Pacific Islanders. The frequencies with which at least one inappropriate medication per visit was prescribed were: 10.8% for females; 8.9% for males; 10.3% for Whites; 9.7% for Blacks; and 1.9% for other minorities.

Discussion

Four or more prescriptions issued per visit and inappropriate prescriptions for the elderly in the United States were evident, and may put a vulnerable aging population at risk of adverse drug events. Copyright © 2002 John Wiley & Sons, Ltd.
The melt extensibility of polypropylene
Authors: Muke S , Ivanov I , Kao N , Bhattacharya S N
Published: August 2002

A Göttfert Rheotens melt strength tester was used to measure the melt strength of several commercially available polypropylene (PP) samples. The melt strengths of the polymer melts investigated were relatively low, in the range 1–10 cN, and were found to be strongly dependent on the extrusion (extrusion flowrate and melt temperature) and drawing (draw distance and draw rate) parameters of the test. A two‐parameter exponential relationship was found between the melt strength of the polymers and the extrusion rate. The melt strength dependence on extrusion rate was defined by a constant parameter, B, which was in the range of 0.003–0.02 and strongly related to the polydispersity of the polymer. An equilibrium melt strength value was found as the extrusion rate tends to zero and was independent of draw distance. Arrhenius temperature dependent flow activation energies determined from the melt strength test were 32–42 kJ mol−1, agreeing with literature values cited for the narrower polydisperse polymers. The relatively low melt strength of conventional linear PPs was enhanced by melt blending with a commercial modifier, EP1, which was a blend of 50 wt% oligocyclopentadiene and 50 wt% PP. Above concentrations of 40 wt% EP1 the melt became phase separated and showed very different behaviour in melt strength. The transient initial stretching and draw ratio at the onset of instability for the Rheotens tensile flow curve were successfully correlated to the melt strength plateau.

© 2001 Society of Chemical Industry
Synthesis of novel superabsorbing copolymers for agricultural and horticultural applications
Authors: Mohana Raju K , Padmanabha Raju M
Published: August 2002

A series of novel superabsorbent copolymers (SAPs) based on monomers acrylamide, calcium acrylate and sodium acrylate have been prepared using ammonium persulfate as initiator and N,N‐methylene‐bis‐acrylamide (MBA) as crosslinking agent; the monomer concentration, MBA concentration and initiator concentration were varied. The experimental results show that the SAPs have good absorbency both in water and NaCl solutions. The copolymers were characterized by IR spectroscopy. Water retention in soil is enhanced by use of these superabsorbents. The effect of SAPs on the growth of bean plants is reported. SAPs may be of use as water management materials for agricultural and horticultural purposes in desert and drought‐prone areas.

© 2001 Society of Chemical Industry
Pan‐milling mixing – a novel approach to forming polymer blends and controlling their morphology
Authors: Chen Zhe , Wang Qi
Published: August 2002

A novel technique (pan‐milling mixing) was developed to control the morphology and thus enhance the mechanical properties of polypropylene/polyamide 6 (PP/PA6) systems. Through pan‐milling at ambient temperature, PP/PA6 pellets of particle size 2–4 mm can be effectively pulverized to well‐mixed micrometre fine powders in the solid state. During pan‐milling of mixtures of PP and PA6, the polymer molecules undergo chain scission and form copolymers that compatibilize the two polymers in situ. By press moulding the finely mixed PP/PA6 powder obtained at a temperature between the melting points of PA6 and PP (for example 200 °C), a blend can be obtained in which the PA6 powder, retained throughout the process in the solid state, is well dispersed in the PP matrix. The mechanical properties of the system are much better than that of PP/PA6 blends prepared by common twin screw extrusion mixing and injection moulding. Tensile strengths of the fine PA6 particle filled PP/PA6 (70/30) blend is 29.3 MPa, which is 6.1 MPa higher than that of a conventionally prepared PP/PA6 blend. The Izod notched impact strength of a fine PA6 particle‐filled PP/PA6 (70/30) blend is 6.34 kJ m−2, which is 1.72 kJ m−2 higher than that of a conventionally prepared PP/PA6 blend. Morphological analysis shows that the domain size of PA6 in the system is much smaller than that of the PP/PA6 blend, and can be controlled by the processing conditions such as temperature.

© 2001 Society of Chemical Industry
Synthesis and biological activity of medium range molecular weight polymers containing exo‐3,6‐epoxy‐1,2,3,6‐tetrahydrophthalimidocaproic acid
Authors: Lee Neung‐Ju , Kang Nam‐In , Cho Won‐Jei , Kim Seon‐Hee , Kang Kyung‐Tae , Theodorakis Emmanuel A
Published: August 2002

A new monomer, exo‐3,6‐epoxy‐1,2,3,6‐tetrahydrophthalimidocaproic acid (ETCA), was prepared by reaction of maleimidocaproic acid and furan. The homopolymer of ETCA and its copolymers with acrylic acid (AA) or with vinyl acetate (VAc) were obtained by photopolymerizations using 2,2‐dimethoxy‐2‐phenylacetophenone as an initiator at 25 °C. The synthesized ETCA and its polymers were identified by FTIR, 1H NMR and 13C NMR spectroscopies. The apparent average molecular weights and polydispersity indices determined by gel permeation chromatography (GPC) were as follows: Mn = 9600 g mol−1, Mw = 9800 g mol−1, Mw/Mn = 1.1 for poly(ETCA); Mn = 14 300 g mol−1, Mw = 16 200 g mol−1, Mw/Mn = 1.2 for poly(ETCA‐co‐AA); Mn = 17 900 g mol−1, Mw = 18 300 g mol−1, Mw/Mn = 1.1 for poly(ETCA‐co‐VAc). The in vitro cytotoxicity of the synthesized compounds against mouse mammary carcinoma and human histiocytic lymphoma cancer cell lines decreased in the following order: 5‐fluorouracil (5‐FU) ≥ ETCA > polymers. The in vivo antitumour activity of the polymers against Balb/C mice bearing sarcoma 180 tumour cells was greater than that of 5‐FU at all doses tested.

© 2001 Society of Chemical Industry
Testing of fluorescent DC lamps for Solar Home Systems
Authors: Narvarte Luis , Muñoz Javier , Lorenzo Eduardo
Published: August 2002

With the advent of the Universal Technical Standard for Solar Home Systems, procedures to test the compliance of SHS fluorescent lamps with the standard have been developed. Definition of the laboratory testing procedures is a necessary step in any lamp quality assurance procedure. Particular attention has been paid to test simplicity and to affordability, in order to facilitate local application of the testing procedures, for example by the organisations which carry out electrification programmes. The set of test procedures has been applied to a representative collection of 42 lamps from many different countries, directly acquired in the current photovoltaic rural electrification market. Tests apply to: lamp resistance under normal operating conditions; lamp reliability under extreme conditions; under abnormal conditions; and lamp luminosity. Results are discussed and some recommendations for updating the relevant standard are given. The selected technical standard, together with the proposed testing procedures, form the basis of a complete quality assurance tool that can be applied locally in normal electrical laboratories. Full testing of a lamp requires less than one month, which is very reasonable on the context of quality assurance programmes. Copyright © 2001 John Wiley & Sons, Ltd.
Body image dissatisfaction and distortion, steroid use, and sex differences in college age bodybuilders
Authors: Peters Mark Anthony , Phelps LeAddelle
Published: August 2002

College age bodybuilders were compared by sex (female, male) and steroid intake (nonuse, use) on two variables: body image dissatisfaction and body image distortion. Results of 2 × 2 ANOVAs (sex by steroid use) revealed only a significant effect for gender on body distortion. No steroid‐use differences were apparent for either body image dissatisfaction or body image distortion. Further analyses indicated that female bodybuilders were equally split between desiring more muscle bulk versus a thinner frame, whereas the majority of male bodybuilders wanted to build more muscle mass. These results are compared to previous research with non‐bodybuilders wherein body image dissatisfaction was unidirectional for females (i.e., all desired slimness) yet bidirectional for males (i.e., some aspired to increased muscle mass whereas others sought a reduction in body fat). © 2001 John Wiley & Sons, Inc.
Dual differentiation: An approach for meeting the curricular needs of gifted students with learning disabilities
Authors: Baum Susan M. , Cooper Carolyn R. , Neu Terry W.
Published: August 2002

Gifted students who experience difficulty with reading, mathematics, spelling, handwriting, and organization frequently become frustrated at an early age. Well‐intentioned teachers attempt to remediate their weaknesses; yet, these youngsters still feel alone in the classroom. Moreover, their academic limitations often mask enormous talent, which seldom has an opportunity to surface. Thus, gifted learning‐disabled students require curriculum that develops their special talents and provides them strategies to compensate for problematic weaknesses. This article discusses the dual characteristics of gifted learning‐disabled students and suggests a unique curriculum that integrates both through talent development. Developed through Project HIGH HOPES, funded federally by the Javits Act (1993–1996), this dually differentiated curriculum offers strategies for addressing students' learning problems while fulfilling their need for sophisticated challenge through advanced‐level content and a focus on solving authentic, real‐world problems. © 2001 John Wiley & Sons, Inc.
Concurrent SN1 and SN2 reactions in the benzylation of pyridines
Authors: Yoh Soo‐Dong , Cheong Duk‐Young , Lee Chung‐Heun , Kim Sung‐Hong , Park Jong‐Hwan , Fujio Mizue , Tsuno Yuho
Published: August 2002

The Menschutkin reactions of 3,4‐methylenedioxybenzyl and 3,4‐dimethoxybenzyl bromides and also p‐methoxybenzyl bromide with Y‐substituted pyridines were kinetically studied for a range of amine concentration in acetonitrile. The strongly activated benzyl bromides showed a significant positive intercept in the plot of the pseudo‐first‐order rate constants against the concentrations of nucleophiles, while less activated benzyl bromides did not give such significant intercepts. The rate data for respective substrates were fitted to the equation kobs = k1 + k2[Nu]. The first‐order rate constant, k1, is unaffected by the nature of the nucleophile, whereas the second‐order rate constant, k2, increased with increasing nucleophilicity. This was ascribed to the simultaneous occurrence of SN1 and SN2 reactions without an intermediate mechanism. These results are taken as evidence for the duality of SN1 and SN2 mechanisms in the Menschutkin reaction in the non‐solvolyzing solvent acetonitrile. Copyright © 2001 John Wiley & Sons, Ltd.
Kinetics and mechanism of methanolysis and cyclization of 1‐acyl‐3‐(2‐halo‐5‐nitrophenyl)thioureas
Authors: Sedlák Miloš , Hanusek Jiří , Holčapek Michal , Štěrba Vojeslav
Published: August 2002

The kinetics of methoxide ion‐catalysed solvolysis of 1‐acyl‐3‐(2‐halo‐5‐nitrophenyl)thioureas and cyclization of fluoro derivatives were studied in methanol at 25 °C. The cyclization involved the substitution of fluorine by sulphur anion of thiourea and proceeded in two steps. With the acetyl derivative, the first step is methanolysis and the second step is much slower cyclization of the 2‐fluoro‐5‐nitrophenylthiourea anion formed to give 2‐amino‐5‐nitro‐1,3‐benzothiazole. With the benzoyl derivative, the first step involves parallel methanolysis of the benzoyl group and cyclization to 2‐benzoylamino‐5‐nitro‐1,3‐benzothiazole. At concentrations of sodium methoxide higher than ca 0.01 mol l−1 the rates of solvolyses of all the acyl halothioureas decreased and at concentrations higher than ca 0.4 mol l−1 there was an increase in the formation of other product(s) than the product of cyclization. After the addition of 18‐crown‐6, the side products were not formed and the cyclizations of fluoro derivatives were considerably accelerated. The slowing of the solvolytic reaction and acceleration of the cyclization reaction are most probably due to the formation of dianions. Copyright © 2001 John Wiley & Sons, Ltd.
A vibrational spectroscopic study of clathrates of resorcarene‐based cavitands
Authors: Dormann Jörg , Ruoff Andreas , Schatz Jürgen , Middel Oskar , Verboom Willem , Reinhoudt David N.
Published: August 2002

By comparison of the fully assigned vibrational spectra obtained for resorcarene‐based cavitands 2a and 2b, their clathrates with toluene and ethanol respectively, and free guest molecules, good structural models for the clathrates could be obtained merely based on Fourier transform infrared data. Using this novel technique, various different interactions between the host and guest in the solid state as well as the orientation of the included guest could be identified. In the case of cavitand 2a, the model obtained by this methodology could be validated by comparison with an experimental crystal structure analysis. Copyright © 2001 John Wiley & Sons, Ltd.
Pulsed‐laser polymerization‐gel permeation chromatographic determination of the propagation‐rate coefficient for the methyl acrylate dimer: A sterically hindered monomer
Authors: Tanaka Kenta , Yamada Bunichiro , Fellows Christopher M. , Gilbert Robert G. , Davis Thomas P. , Yee Lachlan H. , Smith Gregory B. , Rees Mark T. L. , Russell Gregory T.
Published: August 2002

The methyl acrylate dimer (MAD) is a sterically hindered macromonomer, and the propagating radical can fragment to an unsaturated end group. The propagation‐rate coefficient (kp) for MAD was obtained by pulsed‐laser polymerization (PLP). The Mark–Houwink–Sakaruda parameters required for the analysis of the molecular weight distributions (MWDs) were obtained by multiple‐detector gel permeation chromatography (GPC) with on‐line viscometry. The small radical created by the fragmentation results in a short‐chain polymer that means the MWD may no longer be given by that expected for “ideal” PLP conditions; simulations suggest that the degree of polymerization required for “ideal” PLP conditions can be obtained from the primary point of inflection provided the GPC traces also show a clear secondary inflection point (radicals terminated by the second, rather than the first, pulse subsequent to initiation). Over the temperature range of 40–75 °C, the data can be best fitted by kp/dm3 mol−1 s−1 = 106.1 exp(−29.5 kJ mol−1), with a moderately large joint confidence interval for the Arrhenius parameters. The data are consistent with an increased activation energy and reduced frequency factor as compared with acrylate or methacrylate; both of these changes can be ascribed to hindrance. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3902–3915, 2001
Copolymerization of propylene with higher α‐olefins in the presence of the syndiospecific catalyst i‐Pr(Cp)(9‐Flu)ZrCl2/MAO
Authors: Graef Sven M. , Wahner Udo M. , Van Reenen Albert J. , Brüll Robert , Sanderson Ronald D. , Pasch Harald
Published: August 2002

The catalyst system i‐Pr(Cp)(9‐Flu)ZrCl2/methylaluminoxane was used for the synthesis of random syndiotactic copolymers of propylene with 1‐hexene, 1‐dodecene, and 1‐octadecene as comonomers. An investigation of the microstructure by 13C NMR spectroscopy revealed that the stereoregularity of the copolymers decreased because of an increase in skipped insertions in the presence of the higher 1‐olefin. The melting temperature of the copolymers, as measured by differential scanning calorimetry (DSC), decreased linearly with increasing comonomer content independently of the comonomer nature. During the DSC heating cycle, an exothermic peak indicating a crystallization process was observed. The decrease in the crystallization temperature with higher 1‐olefin content, measured by crystallization analysis fractionation, indicated a small but significant dependence on the nature of the comonomer. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 128–140, 2002
Microstructure analysis and thermal property of copolymers made of glycolide and ϵ‐caprolactone by stannous octoate
Authors: Pack Ji Won , Kim Soo Hyun , Cho I‐Whan , Park Soo Young , Kim Young Ha
Published: August 2002

Glycolide (GL) and ϵ‐caprolactone (CL) were copolymerized in bulk at relatively high temperatures using stannous octoate as a catalyst. To investigate the relationship among microstructure, thermal properties, and crystallinity, three series of copolymers prepared at various reaction temperatures, times, and comonomer feed ratios were prepared and characterized by 1H and 13C NMR, DSC, and wide‐angle X‐ray diffraction (WAXD). The 600‐MHz 1H NMR spectra provided information about not only the copolymer compositions but also about the chain microstructure. The reactivity ratios (rG and rC) were calculated from the monomer sequences and were 6.84 and 0.13, respectively. In terms of overall feed compositions, the sequence lengths of the glycolyl units calculated from the reactivity ratios exceeded those measured from the polymeric products. Mechanistic considerations based on reactivity ratios, monomer consumption data, and average sequence lengths are discussed. The unusual phase diagram of GL/CL copolymers implies that the copolymer melting temperature does not depend on its composition alone but rather on the nature of the sequence distribution. The DSC and WAXD measurements show a close relationship between polymer crystallinity and the nature of the polymer sequence. © 2002 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 544–554, 2002; DOI 10.1002/pola.10123
Epoxy resins from novel monomers with a bis‐(9,10‐dihydro‐9‐oxa‐10‐oxide‐10‐phosphaphenanthrene‐10‐yl‐) substituent
Authors: Liu Ying Ling
Published: August 2002

A new diepoxide and a new diamine, both bearing bis‐(9,10‐dihydro‐9‐oxa‐10‐oxide‐10‐phosphaphenanthrene‐10‐yl‐)‐substituted methylene linkages, were prepared through the reaction of 9,10‐dihydro‐oxa‐10‐phosphaphenanthrene‐10‐oxide with benzophenone derivatives via a simple addition reaction followed by a dehydration reaction. These two compounds were used as monomers for preparing cured epoxy resins with high phosphorus contents. The resultant epoxy resins showed high glass‐transition temperatures (between 131 and 196 °C). All of the cured epoxy resins exhibited high thermal stability, with 5% weight loss temperatures over 316 °C, and excellent flame retardancy, with limited oxygen index values of 37–50. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 359–368, 2002
Synthesis and properties of aromatic poly(ester amide)s with pendant phosphorus groups
Authors: Liou Guey‐Sheng , Hsiao Sheng‐Huei
Published: August 2002

Two series of phosphorus‐containing aromatic poly(ester amide)s with inherent viscosities of 0.46–3.20 dL/g were prepared by low‐temperature solution polycondensation from 1,4‐bis(3‐aminobenzoyloxy)‐2‐(6‐oxido‐6H‐dibenz〈c,e〉〈1,2〉oxaphosphorin‐6‐yl)naphthalene and 1,4‐bis(4‐aminobenzoyloxy)‐2‐(6‐oxido‐6H‐dibenz〈c,e〉〈1,2〉oxaphosphorin‐6‐yl)naphthalene with various aromatic diacid chlorides. All the poly(ester amide)s were amorphous and readily soluble in many organic solvents, such as N,N‐dimethylformamide, N,N‐dimethylacetamide (DMAc), and N‐methyl‐2‐pyrrolidone (NMP). Transparent, tough, and flexible films of these polymers were cast from DMAc and NMP solutions. Their casting films had tensile strengths of 71–214 MPa, elongations to break of 5–10%, and initial moduli of 2.3–6.0 GPa. These poly(ester amide)s had glass‐transition temperatures of 209–239 °C (m‐series) and 222–267 °C (p‐series). The degradation temperatures at 10% weight loss in nitrogen for these polymers ranged from 462 to 489 °C, and the char yields at 800 °C were 55–63%. Most of the poly(ester amide)s also showed a high char yield of 35–45%, even at 800 °C under a flow of air. The limited oxygen indices of these poly(ester amide)s were 35–46. © 2002 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 459–470, 2002; DOI 10.1002/pola.10129
Solid polymer electrolytes. IV. Preparation and characterization of novel crosslinked epoxy‐siloxane polymer complexes as polymer electrolytes
Authors: Liang Wuu‐Jyh , Kuo Chao‐Ling , Lin Chia‐Liang , Kuo Ping‐Lin
Published: August 2002

Two series of novel crosslinked siloxane‐based polymers and their complexes with lithium perchlorate (LiClO4) were prepared and characterized by Fourier transform infrared spectroscopy, solid‐state NMR (13C, 29Si, and 7Li nuclei), and differential scanning calorimetry. Their thermal stability and ionic conductivity of these complexes were also investigated by thermogravimetric and AC impedance measurements. In these polymer networks, poly(propylene oxide) chains with different molecular weights were introduced through self‐synthesized epoxy‐siloxane precursors cured with two curing agents. The glass‐transition temperature (Tg) of these copolymers is dependent on the length of the ether units. The dissolution of LiClO4 considerably increases the Tg of the polyether segments. The dependence of the ionic conductivity was investigated as a function of temperature, LiClO4 concentration, and the molecular weight of the polyether segments. The ion‐transport behavior was affected by the combination of the ionic mobility and number of carrier ions. The 7Li solid‐state NMR line shapes of these polymer complexes suggest a significant interaction between Li+ ions and the polymer matrix, and temperature‐ and LiClO4 concentration‐dependent chemical shifts are correlated with ionic conductivity. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1226–1235, 2002
Facile synthesis of high molecular weight aromatic polyformals containing phthalazinone moiety
Authors: Meng Y. Z. , Tjong S. C. , Wang S. J. , Hay A. S.
Published: August 2002

High molecular weight aromatic polyformals containing phthalazinone moiety were simply synthesized with a high‐intensity mixing methodology without the presence of phase‐transfer catalyst. Aromatic polyformals can readily be afforded in a very short time and at temperatures ranging from 50 to 140 °C. These polyformals showed high glass‐transition temperatures together with superior thermal properties when compared with a 4,4′‐isopropylidenediphenol (BPA)‐type polyformal and polycarbonate. The glass‐transition temperatures of these aromatic polyformals ranged from 94 to 229 °C. The molecular weights of the polyformals were examined by gel permeation chromatographic technology, and the result showed that the cyclic formation during the condensation could be dramatically reduced at elevated temperature. The molecular weights and solubility increased with an increasing content of bisphenol A in the polyformals. The result demonstrated that the aromatic polyformal with 50% phthalazinone moiety showed the comparable thermal properties with commercial BPA polycarbonate. This method promisingly opened an effective approach to synthesize aromatic polyformals with high molecular weight and without cyclic formations. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1441–1448, 2002
Phenothiazine photosensitizers for onium salt photoinitiated cationic polymerization
Authors: Gomurashvili Zaza , Crivello James V.
Published: August 2002

Phenothiazine compounds bearing a wide range of different substituents are excellent photosensitizers for onium salt cationic photoinitiators. These photosensitizers are generally operative in the mid‐ and long‐range regions of the UV spectrum and are especially useful for enhancing the rate of photoinitiated cationic polymerization carried out utilizing both filtered and broadband UV emission sources. In this article, the syntheses of several different substituted phenothiazines are described and the ability of these compounds to photosensitize the photolysis of different onium salt photoinitiators is evaluated. Attempts were made to correlate the structure and spectral characteristics of the phenothiazines with their efficiency of photosensitization in the cationic photopolymerizations of several typical epoxide and vinyl ether monomers. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1187–1197, 2001
A study on acrylamide polymerization by anodic contact glow‐discharge electrolysis: A novel tool
Authors: Sengupta Susanta K. , Sandhir Urvashi , Misra Nira
Published: August 2002

Contact glow‐discharge electrolysis (CGDE) is an unconventional electrolytic phenomenon in which a plasma is sustained by a direct current (dc) glow‐discharge between an electrode and the liquid electrolyte around it. A remarkable feature of CGDE is highly nonfaradaic chemical effects at the glow‐discharge electrode. During anodic CGDE of an aqueous electrolyte, non‐Faradaic yields originate mainly from reactions triggered by H• and OH• radicals generated in high local concentrations near the anodic plasma/liquid electrolyte interface during the process. The radical‐generating potentiality of anodic CGDE was explored for the polymerization of acrylamide in aqueous media. The percentage of monomer conversion, rate of polymerization, charge efficiency, and viscometric average molar mass of the polymers produced were measured as functions of the quantities of electricity passed. The charge efficiency of the polymerization of acrylamide by anodic CGDE was at least 1 order of magnitude higher than that of ordinary electrochemically initiated polymerization. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1584–1588, 2001
Thermal stability of brominated poly(isobutylene‐co‐isoprene)
Authors: Parent J. Scott , Thom Darren J. , White Greg , Whitney Ralph A. , Hopkins William
Published: August 2002

The thermal stability of brominated isobutylene–isoprene rubber (BIIR) was investigated through studies of the elastomer and a model compound that accurately represented the reactive functionality within the polymer. An analysis of commercial BIIR and reaction products of brominated 2,2,4,8,8‐pentamethyl‐4‐nonene (BPMN) by NMR demonstrated that bromination of isobutylene–isoprene rubber by 1,3‐dibromo‐5,5‐dimethylhydantoin yielded a kinetically favored exomethylene substitution product, 3‐bromo‐6,6‐dimethyl‐2‐(2,2‐dimethylpropyl)‐1‐heptene (2), as opposed to the more stable endo‐isomer, (E,Z)‐4‐(bromomethyl)‐2,2,8,8‐tetramethyl‐4‐nonene (3). The exposure of BIIR and the brominated model compound BPMN to vulcanization temperatures led to the isomerization of 2 to 3 at a rate strongly dependent on HBr concentration. The elimination of HBr from these allylic bromides to produce exo‐ and endo‐conjugated dienes proceeded concurrently with isomerization, and the kinetics of these processes could be rationalized on the basis of a polar reaction mechanism. The product distributions obtained from both the model system and BIIR were consistent, thereby justifying an extension of the model compound approach to an analysis of BIIR vulcanization chemistry. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2019–2026, 2001
Preparation and properties of polybenzoxazine/poly(imide‐siloxane) alloys: In situ ring‐opening polymerization of benzoxazine in the presence of soluble poly(imide‐siloxane)s
Authors: Takeichi Tsutomu , Agag Tarek , Zeidam Rachib
Published: August 2002

Benzoxazine monomer (Ba) was blended with soluble poly(imide‐siloxane)s in various weight ratios. The soluble poly(imide‐siloxane)s with and without pendent phenolic groups were prepared from the reaction of 2,2′‐bis(3,4‐dicarboxylphenyl)hexafluoropropane dianhydride with α,ω‐bis(aminopropyl)dimethylsiloxane oligomer (PDMS; molecular weight = 5000) and 3,3′‐dihydroxybenzidine (with OH group) or 4,4′‐diaminodiphenyl ether (without OH group). The onset and maximum of the exotherm due to the ring‐opening polymerization for the pristine Ba appeared on differential scanning calorimetry curves around 200 and 240 °C, respectively. In the presence of poly(imide‐siloxane)s, the exothermic temperatures were lowered: the onset to 130–140 °C and the maximum to 210–220 °C. The exotherm due to the benzoxazine polymerization disappeared after curing at 240 °C for 1 h. Viscoelastic measurements of the cured blends containing poly(imide‐siloxane) with OH functionality showed two glass‐transition temperatures (Tg's), at a low temperature around −55 °C and at a high temperature around 250–300 °C, displaying phase separation between PDMS and the combined phase consisting of polyimide and polybenzoxazine (PBa) components due to the formation of AB‐crosslinked polymer. For the blends containing poly(imide‐siloxane) without OH functionalities, however, in addition to the Tg due to PDMS, two Tg's were observed in high‐temperature ranges, 230–260 and 300–350 °C, indicating further phase separation between the polyimide and PBa components due to the formation of semi‐interpenetrating networks. In both cases, Tg increased with increasing poly(imide‐siloxane) content. Tensile measurements showed that the toughness of PBa was enhanced by the addition of poly(imide‐siloxane). Thermogravimetric analysis showed that the thermal stability of PBa also was enhanced by the addition of poly(imide‐siloxane). © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2633–2641, 2001
Temperature‐induced aggregation of the copolymers of N‐isopropylacrylamide and sodium 2‐acrylamido‐2‐methyl‐1‐propanesulphonate in aqueous solutions
Authors: Szczubiałka Krzysztof , Loska Rafał , Nowakowska Maria
Published: August 2002

A series of random copolymers of N‐isopropylacrylamide (NIPAM) and sodium 2‐acrylamido‐2‐methyl‐1‐propanesulphonate (AMPS) was synthesized by free‐radical copolymerization. The content of AMPS in the copolymers ranged from 1.1 to 9.6 mol %. The lower critical‐solution temperature (LCST) of copolymers in water increased strongly with an increasing content of AMPS. The influence of polymer concentration on the LCST of the copolymers was studied. For the copolymers with a higher AMPS content, the LCST decreased faster with an increasing concentration than for copolymers with a low content of AMPS. For a copolymer containing 1.1 mol % of AMPS the LCST dropped by about 3 °C when the concentration increased from 1 to 10 g/L, whereas for a copolymer containing 9.6 mol % of AMPS the LCST dropped by about 10 °C in the concentration range from 2 to 10 g/L. It was observed that the ionic strength of the aqueous polymer solution very strongly influences the LCST. This effect was most visible for the copolymer with the highest content of AMPS (9.6 mol %) for which an increase in the ionic strength from 0.2 to 2.0 resulted in a decrease in the LCST by about 27 °C (from 55 to 28 °C), whereas for the copolymer containing 1.1 mol % of AMPS the LCST decreased only by about 6 °C (from 37 to 31 °C) when the ionic strength increased from 0.005 to 0.3. The reactivity ratios for the AMPS and NIPAM monomer pairs were determined using different methods. The values of rAMPS and rNIPAM obtained were 11.0–11.6 and 2.1–2.4, respectively. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2784–2792, 2001
High‐refractive‐index thin films prepared from aminoalkoxysilane‐capped pyromellitic dianhydride–titania hybrid materials
Authors: Chang Chao‐Ching , Chen Wen‐Chang
Published: August 2002

High‐refractive‐index aminoalkoxysilane‐capped pyromellitic dianhydride (PMDA)–titania hybrid optical thin films (TP0–TP8) were synthesized and characterized in this study. They were prepared with PMDA, aminopropyltrimethoxysilane, and titanium(IV) isopropoxide via a sol–gel process followed by spin coating and multistep baking. Through adjustments in the concentration and reaction time, the inorganic content in the hybrid thin films could be as high as 59.1 wt %. The Fourier transform infrared results indicated successful bonding between the organic and inorganic moieties. However, residues of the chelating ligands were found in the hybrids with high titania contents, affecting their thermal and optical properties. Field emission scanning electron microscopy results suggested a nanosized domain of the titania segment in the hybrid materials TP0–TP8. An atomic force microscopy study suggested that the hybrid thin films had good planarization. The dispersions of the refractive index and extinction coefficient in the wavelength range 190–900 nm were studied. The refractive indices of the prepared hybrid thin films at 633 nm increased linearly from 1.567 to 1.780 with increasing titania content. However, the Abbe numbers of the hybrid thin films showed an opposite trend. Excellent optical transparence was obtained in the visible region for the prepared hybrid thin films. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3419–3427, 2001
Crystallization studies of isotactic polypropylene containing nanostructured polyhedral oligomeric silsesquioxane molecules under quiescent and shear conditions
Authors: Fu Bruce X. , Yang Ling , Somani Rajesh H. , Zong Steven X. , Hsiao Benjamin S. , Phillips Shawn , Blanski Rusty , Ruth Patrick
Published: August 2002

Crystallization studies at quiescent and shear states in isotactic polypropylene (iPP) containing nanostructured polyhedral oligomeric silsesquioxane (POSS) molecules were performed with in situ small‐angle X‐ray scattering (SAXS) and differential scanning calorimetry (DSC). DSC was used to characterize the quiescent crystallization behavior. It was observed that the addition of POSS molecules increased the crystallization rate of iPP under both isothermal and nonisothermal conditions, which suggests that POSS crystals act as nucleating agents. Furthermore, the crystallization rate was significantly reduced at a POSS concentration of 30 wt %, which suggests a retarded growth mechanism due to the molecular dispersion of POSS in the matrix. In situ SAXS was used to study the behavior of shear‐induced crystallization at temperatures of 140, 145, and 150 °C in samples with POSS concentrations of 10, 20, and 30 wt %. The SAXS patterns showed scattering maxima along the shear direction, which corresponded to a lamellar structure developed perpendicularly to the flow direction. The crystallization half‐time was calculated from the total scattered intensity of the SAXS image. The oriented fraction, defined as the fraction of scattered intensity from the oriented component to the total scattered intensity, was also calculated. The addition of POSS significantly increased the crystallization rate during shear compared with the rate for the neat polymer without POSS. We postulate that although POSS crystals have a limited role in shear‐induced crystallization, molecularly dispersed POSS molecules behave as weak crosslinkers in polymer melts and increase the relaxation time of iPP chains after shear. Therefore, the overall orientation of the polymer chains is improved and a faster crystallization rate is obtained with the addition of POSS. Moreover, higher POSS concentrations resulted in faster crystallization rates during shear. The addition of POSS decreased the average long‐period value of crystallized iPP after shear, which indicates that iPP nuclei are probably initiated in large numbers near molecularly dispersed POSS molecules. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2727–2739, 2001