bluuebunny/crossref_metadata_2025_split huggingface dataset:
Controlled ring‐opening polymerization of propylene oxide catalyzed by double metal‐cyanide complex
Authors: Huang Yi‐Jun , Qi Guo‐Rong , Wang Yu‐Hua 
Published: August 2002

AbstractA double metal‐cyanide catalyst based on Zn3[Co(CN)6]2 was prepared. This catalyst is very effective for the ring‐opening polymerization of propylene oxide. Polyether polyols of moderate molecular weight having low unsaturation (<0.015 meq/g) can be prepared under mild conditions. The molecular weight of polymer is entirely controlled by a reacted monomer‐to‐initiator ratio. The polymers prepared with stepwise addition of monomer exhibit a narrower molecular weight distribution as compared with those prepared with one‐step addition of monomer. Various compounds containing active hydrogen, except basic compounds and low‐carbon carboxylic acid, may be used as initiators. The reaction rate increases with increasing catalyst amount and decreases with rising initiator concentration. Polymerization involves a rapid exchange reaction between the active species and the dormant species. It was also proven that, to a certain extent, the chain termination of this catalytic system is reversible or temporary. 13C NMR analysis showed that the polymer has a random distribution of the configurational sequences and head‐to‐tail regiosequence. It is assumed that the polymerization proceeds via a cationic coordination mechanism. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1142–1150, 2002
Silicon‐methoxide‐modified clays and their polystyrene nanocomposites
Authors: Zhu Jin , Start Paul , Mauritz Kenneth A. , Wilkie Charles A. 
Published: August 2002

AbstractSilicon‐methoxide‐containing modified clays were obtained through cationic exchange between the sodium clay and the ammonium cation of [3‐(trimethoxysilyl)propyl]octadecyldimethylammonium chloride (Si18). The nanocomposites were prepared through bulk polymerization of styrene in which the Si18 clay was dispersed. The silicon‐methoxide offers the possibility of reaction between the methoxide and a clay hydroxyl group to link together the cation and the clay. The nanocomposites were characterized by X‐ray diffraction, transmission electron microscopy, and atomic force microscopy. Their thermal stability and flame retardancy were measured by thermogravimetric analysis (TGA) and cone calorimetry. Linkage between the silicon and the clay apparently occurs in the clay but is not likely to occur in the nanocomposite, perhaps because of the presence of the polystyrene spreading the distance between the reactive sites, which makes reaction more difficult. The results from TGA and cone calorimetry were similar to those obtained with other nanocomposites. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1498–1503, 2002
Microwave‐assisted ring‐opening polymerization of ϵ‐caprolactone
Authors: Liao L. Q. , Liu L. J. , Zhang C. , He F. , Zhuo R. X. , Wan K. 
Published: August 2002

AbstractRing‐opening polymerization of ϵ‐caprolactone was carried out smoothly and effectively with constant microwave powers of 170, 340, 510, and 680 W, respectively, with a microwave oven at a frequency of 2.45 GHz. The temperature of the polymerization ranged from 80 to 210 °C. Poly(ϵ‐caprolactone) (PCL) with a weight‐average molar mass (Mw) of 124,000 g/mol and yield of 90% was obtained at 680 W for 30 min using 0.1% (mol/mol) stannous octanoate as a catalyst. When the polymerization was catalyzed by 1% (w/w) zinc powder, the Mw of PCL was 92,300 g/mol after the reaction mixture was irradiated at 680 W for 270 min. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1749–1755, 2002
Novel neodymium (III) isopropoxide‐methylaluminoxane catalyst for isoprene polymerization
Authors: Dong Weimin , Masuda Toshio 
Published: August 2002

AbstractA novel catalyst composed of neodymium (III) isopropoxide [Nd(OiPr)3] and methylaluminoxane (MAO) was examined in isoprene polymerization. The Nd(OiPr)3‐MAO catalyst proved to be highly effective in heptane even at low [Al]/[Nd] ratios (ca. 30) to give polyisoprene that possessed high cis‐1,4 stereoregularity (> ca. 90%), a high number‐average molecular weight (Mn ∼105), and relatively narrow molecular weight distributions (Mw/Mn = 1.9–2.8). The catalyst activity increased with an increasing [Al]/[Nd] ratio from 10 to 80 as well as temperature of aging and polymerization from 0 to 60 °C. The polymerization proceeded in the first order with respect to the monomer concentration. Aliphatic solvents (heptane and cyclohexane) achieved a higher yield and Mn of polymer than toluene as a solvent. The Mw/Mn ratio remained around 2.0, and the gel permeation chromatographic curve was always unimodal, indicating that this system is homogeneous and involves a single active site. The microstructure of polyisoprene was determined by IR, 1H NMR, and 13C NMR. The cis‐1,4 contents of the final polymers stayed in the range of 90–92%, regardless of reaction conditions, indicating the high stability of stereospecificity of the catalyst. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1838–1844, 2002
Polymerization of styrene with ionic comonomer, nonionic comonomer, or both
Authors: Xu Xiao‐Jun , Siow Kok‐Siong , Wong Ming‐Keong , Gan Leong‐Ming 
Published: August 2002

AbstractNanosized polystyrene latexes with high polymer contents were obtained from an emulsifier‐free process by the polymerization of styrene with ionic comonomer, nonionic comonomer, or both. After seeding particles were generated in an initial emulsion system consisting of styrene, water, an ionic comonomer [sodium styrenesulfonate (NaSS)] or nonionic comonomer [2‐hydroxyethyl methacrylate (HEMA)], and potassium persulfate, most of the styrene monomer or a mixture of styrene and HEMA was added dropwise to the polymerizing emulsion over 6 h. Stable latexes with high polystyrene contents (≤25%) were obtained. The latex particle weight‐average diameters were largely reduced (41 nm) by the continuous addition of monomer(s) compared with those (117 nm) obtained by the one‐pot polymerization method. Latex particles varied from about 30 to 250 nm in diameters, whereas their molar masses were within 104 to 105 g/mol. The effect of the comonomer concentration on the number of polystyrene particles per milliliter of latex and the weight‐average molar masses of the copolymers during the polymerization are discussed. The surface compositions of the latex particles were analyzed by X‐ray photoelectron spectroscopy, which indicated that the surface of the latex particles was significantly enriched in NaSS, HEMA, or both. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1634–1645, 2001
Reorganization of the structures, morphologies, and conformations of bulk polymers via coalescence from polymer–cyclodextrin inclusion compounds
Authors: Bullions T. A. , Wei M. , Porbeni F. E. , Gerber M. J. , Peet J. , Balik M. , White J. L. , Tonelli A. E. 
Published: August 2002

AbstractBulk poly(ethylene terephthalate) (PET) and bisphenol A polycarbonate (PC) samples have been produced by the coalescence of their segregated, extended chains from the narrow channels of the crystalline inclusion compounds (ICs) formed between the γ‐cyclodextrin (CD) host and PET and PC guests, which are reported for the first time. Differential scanning calorimetry, Fourier transform infrared, and X‐ray observations of PET and PC samples coalesced from their crystalline γ‐CD‐ICs suggest structures and morphologies that are different from those of samples obtained by ordinary solution and melt processing techniques. For example, as‐received PC is generally amorphous with a glass‐transition temperature (Tg) of about 150 °C; when cast from tetrahydrofuran solutions, PC is semicrystalline with a melting temperature (Tm) of about 230 °C; and after PC/γ‐CD‐IC is washed with hot water for the removal of the host γ‐CD and for the coalescence of the guest PC chains, it is semicrystalline but has an elevated Tm value of about 245 °C. PC crystals formed upon the coalescence of highly extended and segregated PC chains from the narrow channels in the γ‐CD host lattice are possibly more chain‐extended and certainly more stable than chain‐folded PC crystals grown from solution. Melting the PC crystals formed by coalescence from PC/γ‐CD‐IC produces a normal amorphous PC melt that, upon cooling, results in typical glassy PC. PET coalesced from its γ‐CD‐IC crystals, although also semicrystalline, displays a Tm value only marginally elevated from that of typical bulk or solution‐crystallized PET samples. However, after the melting of γ‐CD‐IC‐coalesced PET crystals, it is difficult to quench the resultant PET melt into the usual amorphous PET glass, characterized by a Tg value of about 80 °C. Instead, the coalesced PET melt rapidly recrystallizes during the attempted quench, and so upon reheating, it displays neither a Tg nor a crystallization exotherm but simply remelts at the as‐coalesced Tm. This behavior is unaffected by the coalesced PET sample being held above Tm for 2 h, indicating that the extended, unentangled nature of the chains in the noncrystalline regions of the coalesced PET are not easily converted into the completely disordered, randomly coiled, entangled melt. Apparently, the highly extended, unentangled characters of the PC and PET chains in their γ‐CD‐ICs are at least partially retained after they are coalesced. Initial differential scanning calorimetry, thermogravimetric analysis, Fourier transform infrared, and X‐ray observations are described here. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 992–1012, 2002
Phase behavior of tetramethylpolycarbonate blends with styrene‐based methacrylate copolymers and their interaction energies
Authors: Moon E. J. , Kim M. J. , Choi H. K. , Kim C. K. 
Published: August 2002

AbstractThe miscibility of tetramethylpolycarbonate (TMPC) blends with styrenic copolymers containing various methacrylates was examined, and the interaction energies between TMPC and methacrylate were evaluated from the phase‐separation temperatures of TMPC/copolymer blends with lattice‐fluid theory combined with a binary interaction model. TMPC formed miscible blends with styrenic copolymers containing less than a certain amount of methacrylate, and these miscible blends always exhibited lower critical solution temperature (LCST)‐type phase behavior. The phase‐separation temperatures of TMPC blends with copolymers such as poly(styrene‐co‐methyl methacrylate), poly(styrene‐co‐ethyl methacrylate), poly(styrene‐co‐n‐propyl methacrylate), and poly(styrene‐co‐phenyl methacrylate) increase with methacrylate content, go through a maximum, and decrease, whereas those of TMPC blends with poly(styrene‐co‐n‐butyl methacrylate) and poly(styrene‐co‐cyclohexyl methacrylate) always decrease. The calculated interaction energy for a copolymer–TMPC pair is negative and increases with the methacrylate content in the copolymer. This would seem to contradict the prediction of the binary interaction model, that systems with more favorable energetic interactions have higher LCSTs. A detailed inspection of lattice‐fluid theory was performed to explain such phase behavior. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1288–1297, 2002
Conductivity enhancement mechanism of the poly(ethylene oxide)/modified‐clay/LiClO4 systems
Authors: Chen Hsien‐Wei , Chiu Chun‐Yi , Chang Feng‐Chih 
Published: August 2002

AbstractThis study demonstrates that adding clay that was organically modified by dimethyldioctadecylammonium chloride (DDAC) and d2000 surfactants increases the ionic conductivity of polymeric electrolyte. A.C. impedance, differential scanning calorimetric (DSC), and Fourier transform infrared (FTIR) studies revealed that the silicate layers strongly interact with the dopant salt lithium perchlorate (LiClO4) within a poly(ethylene oxide) (PEO)/clay/LiClO4 system. DSC characterization verified that the addition of a small amount of the organic clay reduces the glass‐transition temperature of PEO as a result of the interaction between the negative charge in the clay and the lithium cation. Additionally, the strength of such a specific interaction depends on the extent of PEO intercalation. With respect to the interaction between the silicate layer and the lithium cation, three types of complexes are assumed. In complex I, lithium cation is distributed within the PEO phase. In complex II, lithium cation resides in an PEO/exfoliated‐clay environment. In complex III, the lithium cation is located in PEO/agglomerated‐clay domains. More clay favors complex III over complexes II and I, reducing the interaction between the silicate layers and the lithium cations because of strong self‐aggregation among the silicate layers. Notably, the (PEO)8LiClO4/DDAC‐modified clay (DDAC‐mClay) composition can form a nanocomposite electrolyte with high ionic conductivity (8 × 10−5 S/cm) at room temperature. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1342–1353, 2002
Phase separation in poly(N‐isopropyl acrylamide)/water solutions. II. Salt effects on cloud‐point curves and gelation
Authors: Yang Yanyin , Zeng Fang , Tong Zhen , Liu Xinxin , Wu Shuizhu 
Published: August 2002

AbstractThe cloud‐point temperatures (Tclo's) of poly(N‐isopropyl acrylamide) (PNIPAM)/water solutions with NaCl, NaBr, or NaI were measured. All these salts reduced the Tclo's of PNIPAM/water solutions to different extents, in the following order: NaCl > NaBr > NaI. The higher the concentration of the added salt was, the more greatly Tclo dropped. A dynamic viscoelasticity investigation of the PNIPAM/water solutions with the salts indicated that during phase separation, the system changed from a homogeneous fluid into a physically crosslinked network, and the addition of salts also reduced the temperature at which this change began. The gelation temperature (Tgel) and the scaling exponent of the PNIPAM/water solutions with NaBr were obtained with dynamic scaling theory, and Tgel was found to be close to Tclo. That the addition of salts to the solution decreased Tclo and Tgel to the same extent further proved that the network structure was formed with the phase separation in the PNIPAM/water solutions. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 901–907, 2001
Proton‐conducting poly(vinylpyrrolidon)–polyphosphoric acid blends
Authors: Bozkurt A. , Meyer W. H. 
Published: August 2002

AbstractAnhydrous, proton‐conducting polymer electrolytes of poly(vinylpyrrolidon) (PVP) with polyphosphoric acid (PPA) were prepared. PVP‐x‐PPA blends were obtained for 0.5 ≤ x ≤ 3, where x was the number of moles of PO per polymer repeat unit. Fourier transform infrared studies indicated protonation of the carbonyl group in the five‐member ring. Thermogravimetric analysis showed that these materials were stable up to about 180 °C. Differential scanning calorimetry data demonstrated that the addition of the acid plasticized the material, shifting the glass‐transition temperature from 180 °C for the pure polymer to −23 °C for x = 3. The temperature dependence of the mechanical properties was investigated with shear experiments. The direct‐current conductivity increased with x and reached about 10−5 S/cm at ambient temperature. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1987–1994, 2001
Participation in psychosocial group intervention among Japanese women with primary breast cancer and its associated factors
Authors: Fukui Sakiko , Kugaya Akira , Kamiya Masae , Koike Makiko , Okamura Hitoshi , Nakanishi Tatsuro , Wenner Marcus , Imoto Shigeru , Kanagawa Katsuko , Uchitomi Yosuke 
Published: August 2002

AbstractThough psychosocial group intervention is considered in the West to be an important source of support for reducing psychosocial distress in cancer patients, in Asian countries, there has been no research as yet on the needs for such intervention. This study investigated the level of participation and interest in psychosocial group intervention plus any associated factors in 151 primary breast cancer patients. All were less than 65 years old at 4–18 months post‐surgery. Of the 126 subjects who responded (response rate 83%), 53 (42%) participated (participants) and 73 (58%) did not (non‐participants). Participation was greater among those with a high level of anxiety measured by the Hospital Anxiety and Depression Scale (HADS) (odds ratio [OR], 3.25; 95% confidence interval [CI], 1.07–10.42), those who had undergone surgery within the last 12 months (OR, 3.10; 95% CI, 1.35–7.55), and those who were 50–65 years old (OR, 3.08; 95% CI, 1.33–7.66). Among the non‐participants, 53 (73%) were interested in the intervention while 20 (27%) were not. Non‐participants without any interest in the psychosocial group intervention had significantly higher anxiety levels than those with interest (t=−2.08; df=71; p=0.03).These results suggest that most Japanese breast cancer patients who need psychological support can be sought out by asking whether they are willing to participate in a psychosocial group intervention. However, the minority not interested in any psychological group intervention might need other supports such as medication or individual psychotherapy. Copyright © 2001 John Wiley & Sons, Ltd.
Chemoprevention of breast cancer with selective estrogen receptor modulators: views from broadly diverse focus groups of women with elevated risk for breast cancer
Authors: Cyrus‐David M.S. , Strom S.S. 
Published: August 2002

AbstractSelective estrogen receptor modulators (SERMs) are anti‐estrogens that selectively antagonize the proliferative effects of estrogens on breast cells, thereby inhibiting or reversing neoplastic progression to clinical breast cancer. The goal is to administer these agents to healthy women with an elevated risk for breast cancer. The study reported here assessed the knowledge and attitude of 26 broadly selected women with an elevated risk for breast cancer who participated in three focus groups (eight to ten per group) that discussed the use of SERMs, such as tamoxifen and raloxifen. Data were analyzed by cross‐case procedure using variable‐oriented strategies.Acceptance of breast cancer chemoprevention treatment with SERMs was found to be influenced by various factors, including a knowledge of breast cancer risk factors, the perception of personal risk for breast cancer, and the perception of barriers and benefits to receiving chemoprevention treatment. The issues involved in making the decision to accept treatment with SERMs are discussed. Most of the participants in the groups indicated they were unlikely to accept breast cancer chemoprevention treatment with SERMs. Copyright © 2001 John Wiley & Sons, Ltd.
A model‐based map of ground temperatures for the permafrost regions of Canada
Authors: Henry Kerri , Smith Michael 
Published: August 2002

AbstractA functional model of the permafrost‐climate system is applied at national scale, to produce a map of near‐surface ground temperatures in the permafrost regions of Canada. The TTOP model links the temperature at the top of permafrost (TTOP) to the climate through seasonal surface transfer functions and subsurface thermal properties. The parameters in the model were compiled at national scale for Canada, although the topographic effects of the Western Cordillera were not incorporated into the analysis. The objective of the study was accomplished by implementing the TTOP model within a Geographical Information System. The TTOP map is evaluated against the published Ground Temperature Map of Canada. The published map shows ground temperatures according to a scale of temperature classes, so TTOP values were categorized into the same classes. Across the permafrost regions of Canada, 72.1% of the area is in the same class in both maps, while 27.7% differs by one temperature class. Only 0.2% of the area differs by two temperature classes. The results suggest that the TTOP model can provide a rational and functional basis for relating near‐surface permafrost temperature and climate at national and regional scales. The model could be applied to the assessment of climate change impacts on the magnitude and distribution of permafrost temperatures. Copyright © 2001 John Wiley & Sons, Ltd.
Randomized controlled study of in‐hospital exercise training programs in children with cystic fibrosis
Authors: Selvadurai H.C. , Blimkie C.J. , Meyers N. , Mellis C.M. , Cooper P.J. , Van Asperen P.P. 
Published: August 2002

AbstractThe aim of this study was to compare aerobic and resistance training in children with cystic fibrosis (CF) admitted to hospital with an intercurrent pulmonary infection with a control group. The subjects were randomized into three groups on the first day of admission. The fat‐free mass (FFM) was calculated, using the skin fold thickness from four sites (biceps, triceps, subscapular, and iliac crest). Pulmonary function tests were performed within 36 hr of admission and repeated on discharge from the hospital, and again at 1 month after discharge. All subjects performed an incremental treadmill exercise test, using a modified Bruce protocol. Lower limb strength was measured using a Cybex dynamometer. An assessment of quality of life was made using the Quality of Well Being Scale, as previously reported. Activity levels were measured using a 7‐day activity diary, and subjects also wore an accelerometer on their hips. There were no significant differences between the three groups in terms of disease severity, and length of stay in hospital. Subjects in all three groups received intravenous antibiotics and nutritional supplementation as determined by the physician. Children randomized to the aerobic training group participated in aerobic activities for five sessions, each of 30‐min duration, a week. The children randomized to the resistance training group exercised both upper and lower limbs against a graded resistance machine. Subjects in the control group received standard chest physiotherapy.Our study demonstrated that children who received aerobic training had significantly better peak aerobic capacity, activity levels, and quality of life than children who received the resistance training program. Children who received resistance training had better weight gain (total mass, as well as fat‐free mass), lung function, and leg strength than children who received aerobic training.A combination of aerobic and resistance training may be the best training program, and future studies to assess optimal training programs for CF patients are indicated. Pediatr Pulmonol. 2002; 33:194–200. © 2002 Wiley‐Liss, Inc.