bluuebunny/crossref_metadata_2025 huggingface dataset:
Stress analysis around holes or notches by special finite elements
Authors: de Miranda Stefano , Ubertini Francesco
Published: November 2005

In this paper, three special elements for stress concentration analysis around holes or notches are presented. One is based on a variational principle involving displacements, unsymmetric stresses and rotations as independent variables, the other two on the classical Hellinger–Reissner principle. The new elements are designed to be used in a single layer along the cavity rim, where enhanced properties are needed to get a satisfactory level of accuracy. Special properties are obtained by enforcing the stress approximation to satisfy a priori the traction‐free boundary condition on the element side positioned along the cavity rim and by properly enriching the displacement interpolation. The proposed elements are: applicable to geometries of arbitrary shape, easy‐to‐use, low‐cost and readily implementable into existing finite‐element codes. Copyright © 2005 John Wiley & Sons, Ltd.
Peroxidase‐catalyzed polymerization and copolymerization of lignin‐based macromonomer (lignocresol) having high content of p‐cresol and thermal properties of the resulting polymers
Authors: Yoshida Takashi , Xia Zuyong , Takeda Kei‐ichi , Katsuta Takahiro , Sugimoto Kazutoshi , Funaoka Masamitsu
Published: November 2005

Peroxidase‐catalyzed polymerization of lignin‐based macromonomer, lignocresol, which was prepared by the phase‐separation system of lignin and p‐cresol in aqueous sulfuric acid, was carried out for the first time in aqueous organic solvents to give insoluble polymers in 55% yield. It was found that the polymerizability of lignocresol by peroxidase was enhanced by the introduction of p‐cresol in lignin side‐chains compared to that of original lignin. Copolymerization of lignocresol with p‐cresol gave the corresponding copolymers in high yields. From the IR results, lignocresol might be polymerized through a phenoxyl radical. The pyrolysis gas chromatography‐mass spectrometry (GC‐MS) analysis of the polymers obtained indicated that the polymerization of lignocresol involved mainly the oxidative coupling at the introduced p‐cresol. The thermal properties of the polymers obtained were characterized by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) measurements, suggesting that the polymers have high thermal stability according to the crosslinked structures. Copyright © 2005 John Wiley & Sons, Ltd.
Synovial fluid macrophages are capable of osteoclast formation and resorption
Authors: Adamopoulos IE , Sabokbar A , Wordsworth BP , Carr A , Ferguson DJ , Athanasou NA
Published: November 2005

To determine whether synovial fluid (SF) macrophages isolated from the SF of osteoarthritis (OA), rheumatoid arthritis (RA) and pyrophosphate arthropathy (PPA) joints are capable of osteoclast formation, and to investigate the cellular and humoral factors required for this to occur, SF macrophages (CD14+) were isolated from the knee joint SF from patients with OA, RA and PPA and cultured for up to 14 days with macrophage‐colony stimulating factor (M‐CSF) and soluble receptor activator for nuclear factor‐κB ligand (RANKL) or tumour‐necrosis factor‐α (TNFα) and interleukin‐1α (IL‐1α). Osteoclast differentiation was assessed by expression of tartrate‐resistant acid phosphatase (TRAP) and vitronectin receptor (VNR), F‐actin ring formation and lacunar resorption. Osteoclast formation and lacunar resorption was seen in RANKL‐treated cultures of SF macrophages isolated from OA, RA and PPA joints with the largest amount of resorption noted in RA and PPA SF macrophage cultures. In TNFα/IL‐1α‐treated RA and PPA SF macrophage cultures, osteoclasts capable of lacunar resorption were also formed. Lacunar resorption was more extensive in RANKL than TNFα/IL‐1α‐treated cultures. These findings indicate that SF macrophages are capable of differentiating into mature osteoclasts capable of lacunar resorption. M‐CSF in combination with RANKL or TNFα/IL‐1α was required for osteoclast formation. As inflammatory synovial fluids contain an increase in the number of macrophages and an increase in the amounts of RANKL, TNFα and IL‐1α, these findings suggest that one means whereby bone erosions may form in rheumatoid or crystal arthritis is by differentiation of synovial fluid macrophages into osteoclasts. Copyright © 2005 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Inducible nitric oxide synthase activity correlates with lymphangiogenesis and vascular endothelial growth factor‐C expression in head and neck squamous cell carcinoma
Authors: Franchi Alessandro , Massi Daniela , Santucci Marco , Masini Emanuela , Degl'Innocenti Duccio Rossi , Magnelli Lucia , Fanti Elena , Naldini Antonella , Ardinghi Camilla , Carraro Fabio , Gallo Oreste
Published: November 2005

Nitric oxide (NO) is a diatomic free radical molecule that has been implicated in tumour angiogenesis and progression of head and neck squamous cell carcinoma (HNSCC). However, the mechanism underlying the effect of NO on tumour spread remains largely unknown. Tumour lymphangiogenesis has recently received considerable attention and there is increasing evidence that it is relevant for metastasis to lymph nodes in HNSCC. Here, we study the correlation between inducible NOS synthase (iNOS) activity and lymphangiogenesis in a series of 60 HNSCCs and the possible involvement of the lymphangiogenic factor vascular endothelial growth factor (VEGF)‐C. HNSCC presenting with lymph node metastasis had a significantly higher lymphatic vessel density in both the tumour mass and the peritumour area (p = 0.006 and p = 0.001, respectively). Similarly, tumours with lymph node metastasis showed greater lymphatic vessel area than tumours with no lymph node involvement (p = 0.001 for intratumour lymphatics and p < 0.001 for peritumour lymphatics). iNOS activity measured in specimens from the tumour periphery correlated strongly with both lymphatic vessel density and lymphatic vessel area (p = 0.01, rs = 0.45 and p < 0.001, rs = 0.725, respectively). Conversely, these correlations were not observed in specimens from the tumour core. In addition, VEGF‐C mRNA expression was significantly elevated in tumours with high iNOS activity (p = 0.008, rs = 0.563), and VEGF‐C expression correlated positively with the presence of lymph node metastases (p = 0.03). In vitro, in the A431 human squamous carcinoma cell line, exogenous and endogenous stimulation of the iNOS pathway led to up‐regulation of VEGF‐C, which was blocked by the NOS inhibitor L‐NNA. Taken together, our results indicate that iNOS activity may promote lymphangiogenesis and spread to lymph nodes in HNSCC, with the possible involvement of VEGF‐C. Copyright © 2005 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Differentiation of rhabdomyosarcoma cell lines using retinoic acid
Authors: Barlow Jason W. , Wiley Joe C. , Mous Marieke , Narendran Aru , Gee Matthew F.W. , Goldberg Michael , Sexsmith Elizabeth , Malkin David
Published: November 2005

Background

Rhabdomyosarcoma (RMS) is the most frequent sporadic soft tissue sarcoma of childhood and adolescence. The overall 5‐year survival rate for patients with RMS is 70% with the use of surgery, radiation, and chemotherapy. Novel therapeutic approaches are necessary to improve on these outcomes particularly among the more aggressive alveolar RMS (ARMS) and late stages of disease, where 5‐year survival is less than 20%. Retinoids have been successfully used in the treatment of acute promyelocytic leukemia (APML) and neuroblastoma.

Purpose

However, analysis of retinoids as a differentiating agent for RMS has been incomplete. This work examined the ability of retinoic acid (RA) to promote differentiation of RMS cell lines by examining the expression of myogenic proteins in five RMS cell lines in response to All‐trans Retinoic Acid (ATRA) or 9‐cis retinoic acid (CRA).

Results

Analysis of growth curves indicates that both retinoids suppress cell growth of Rh4 and Rh28. RD cells only responded to‐CRA whereas Rh30 and Rh18 did not respond. Following treatment with ATRA FACS analysis showed an altered cell cycle with the same pattern as the growth curves. ATRA altered cellular morphology of two cell lines, Rh4 and Rh28, and induced Troponin T expression in these cells suggesting a differentiating effect.

Conclusions

These studies suggest that retinoids are effective inducers of growth arrest and differentiation in some RMS cell lines, and offer a basis for further in vivo testing in mice of ATRA as a potential approach to ARMS treatment. Pediatric Blood Cancer 2006;47:773–784. © 2005 Wiley‐Liss, Inc.
Hepatoblastoma in a child with neurofibromatosis type I
Authors: Uçar Canan , Çalışkan Ümran , Toy Hatice , Günel Engin
Published: November 2005

A major hallmark of NF1 is the development of benign tumors, including peripheral neurofibromas, plexiform neurofibromas, gliomas of the optic tract, other low grade gliomas, and pheochromocytomas. Hepatoblastoma have not been previously reported in patients with neurofibromatosis type 1. We present a case of a 9‐month‐old boy diagnosed with both hepatoblastoma and neurofibromatosis type 1. Hepatoblastoma occurs in association with several well‐described cancer predisposition syndromes, including familial adenomatous polyposis, Beckwith–Wiedemann syndrome, Li‐Fraumeni syndrome, trisomy 18, and glycogen storage disease type I. This paper describes a case of hepatoblastoma diagnosed in association with neurofibromatosis type 1. Pediatr Blood Cancer 2007;49:357–359. © 2005 Wiley‐Liss, Inc.
Pulmonary Langerhans cell histiocytosis: A variable disease in childhood
Authors: Odame Isaac , Li Patricia , Lau Loretta , Doda Wendy , Noseworthy Mary , Babyn Paul , Weitzman Sheila
Published: November 2005

Background

Pulmonary Langerhans cell histiocytosis (PLCH) is rare in childhood but occurs most commonly in children with multisystem (MS) LCH. In adults, by contrast, the lung is the most common and usually the sole organ affected. This retrospective study describes the clinical manifestation, course, and outcome of PLCH in children consecutively diagnosed at two Canadian institutions.

Procedure

The medical records of children (<18 years of age) consecutively diagnosed with LCH at the two stitutions, were examined to ascertain the demographic details, pathological diagnosis, and organs involved. Further clinical details including, the clinical manifestation, details of therapy, course of lung disease, and clinical outcome were extracted for patients with PLCH. Initial and follow‐up lung radiographs and CT scans were re‐reviewed.

Results

Of the 178 patients with LCH, 40 (22.5%) presented with MS disease. Thirteen (7.3%) had PLCH, seven at initial diagnosis, and six at the time of disease progression. The median age was 10.1 months and mean was 11.9 months at diagnosis of PLCH. Lung involvement was always in the context of MS LCH, and half of the patients had no respiratory symptoms. Disease‐free survival was around 70%, with a mean follow‐up duration of 7 years. Of the four patients who died, three had other risk‐organ involvement. Five of the nine surviving patients have had complete radiological resolution of PLCH.

Conclusion

PLCH is seen in less than 10% of childhood LCH, but more than 30% of MS LCH. About half of children with PLCH may be asymptomatic, and the prognosis appears to depend on the presence or absence of other risk‐organ involvement. The MS PLCH found in children appears to be a different disease from the single system (SS) PLCH seen in adults. © 2005 Wiley‐Liss, Inc.
Acute myeloid leukemia in a child with hereditary thrombocytopenia
Authors: Rheingold Susan R.
Published: November 2005

A child with a known diagnosis of an autosomal dominant macrothrombocytopenia, Fechtner Syndrome, developed acute myeloid leukemia (AML). Recently the disease gene for the inherited macrothrombocytopenias has been identified as MYH9, encoding for non‐muscle myosin heavy chain‐A. MYH9 has never been associated with the development of acute leukemia, but MYH11 is disrupted in the M4 eosinophilia sub‐type of AML (inv16). The patients leukemic blasts did carry the common t(8;21) which yields an AML1–ETO fusion protein that inhibits AML‐1. Despite his thrombocytopenia, the patient successfully completed intensive bone marrow cytoreduction without significant bleeding complications and is now in remission for over 3 years. Pediatr Blood Cancer 2007;48:105–107. © 2005 Wiley‐Liss, Inc.
Time‐dependence of piezo‐resistive behavior for polyethylene/foliated graphite nanocomposites
Authors: Chen Guohua , Lu Jinrong , Lu Wei , Wu Dajun , Wu Cuiling
Published: November 2005

High‐density polyethylene (HDPE)/foliated graphite (FG) nanocomposites were prepared by blending HDPE with FG fillers. This nanocomposites exhibited much more distinct piezo‐resistive behavior (electric response under applied pressure), when compared with conventional conducting polymer composites. In this paper, the time‐dependences of piezo‐resistance, reproducibility and stability of the piezo‐resistive behavior for HDPE/FG nanocomposites are investigated. It is shown that the time‐dependence of piezo‐resistive behavior strongly depends on the fixed pressure and FG concentration. Under a lower fixed pressure, the relative resistance decreases with time, whereas the composite resistance increases with time under a higher fixed pressure. The shift of relative resistance changes more slowly at higher filler concentrations. The average ‘nanosheet’ separation in the nanocomposite changing with time under fixed pressures is the origin of the time‐dependent piezo‐resistive behavior. Copyright © 2005 Society of Chemical Industry
2,6‐Diamino‐4‐phenylphenol (DAPP) copolymerized polyimides: synthesis and characterization
Authors: Chen Bor‐Kuan , Tsai Yu‐Jie , Tsay Sun‐Yuan
Published: November 2005

Novel soluble copolyimides containing phenyl and hydroxyl pendant groups were synthesized from pyromellitic dianhydride (PMDA) and two diamines, 2,6‐diamino‐4‐phenylphenol (DAPP) and 4,4′‐oxydianiline (ODA), in various ratios via thermal imidization. The structures and physical properties of the copolyimides were characterized by FTIR, elemental analysis, DSC, dynamic mechanical analysis (DMA), TGA, a universal testing machine for stress–strain behaviour, and a dielectric analyzer to study the effect of DAPP on the physical properties of the modified polymers. Copolyimides containing more than 40 mol% DAPP were soluble in hot N‐methyl‐2‐pyrrolidone (NMP), dimethylacetamide (DMAc) and dimethylformamide (DMF), and possessed a high glass transition temperature (358 °C) and a high modulus (3.9 GPa). Introduction of the diamine DAPP could also reduce the dielectric constant. A segment of imide linkages could convert to benzoxazole linkages by decarboxylation at temperatures higher than 420 °C under vacuum. Although the heat‐treated polybenzoxazoles (PBOs) exhibited many good properties, they were found to be too rigid and brittle to be processable for microelectronic applications. Copyright © 2005 Society of Chemical Industry
Virtual identification of essential proteins within the protein interaction network of yeast
Authors: Estrada Ernesto
Published: November 2005

Topological analysis of large scale protein‐protein interaction networks (PINs) is important for understanding the organizational and functional principles of individual proteins. The number of interactions that a protein has in a PIN has been observed to be correlated with its indispensability. Essential proteins generally have more interactions than the nonessential ones. We show here that the lethality associated with removal of a protein from the yeast proteome correlates with different centrality measures of the nodes in the PIN, such as the closeness of a protein to many other proteins, or the number of pairs of proteins which need a specific protein as an intermediary in their communications, or the participation of a protein in different protein clusters in the PIN. These measures are significantly better than random selection in identifying essential proteins in a PIN. Centrality measures based on graph spectral properties of the network, in particular the subgraph centrality, show the best performance in identifying essential proteins in the yeast PIN. Subgraph centrality gives important structural information about the role of individual proteins, and permits the selection of possible targets for rational drug discovery through the identification of essential proteins in the PIN.
TEMPO‐mediated dispersion polymerization of styrene in the presence of camphorsulfonic acid
Authors: Oh Sejin , Kim Kijung , Lee Byung H. , Shim Sang Eun , Choe Soonja
Published: November 2005

The TEMPO‐mediated polymerization of styrene in the presence of camphorsulfonic acid (CSA) is carried out using controlled radical dispersion polymerization. In the absence of TEMPO and CSA, 92% of conversion was achieved within 3 h of polymerization. When TEMPO is solely used, broadening of particle size with narrow PDI was observed because of the prolonged polymerization time. However, when 1:1 molar ratio of CSA/TEMPO was added, the fairly monodisperse PS microspheres having 5.83 μm average size and 3.42% CV (coefficient of variation) were successfully achieved because of the narrow molecular weight of intermediate oligomers and shortening of the polymerization time. This result obviously indicates that the addition of CSA in TEMPO‐mediated dispersion polymerization not only shortens the polymerization time but also greatly improves the uniformity of the microspheres. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 62–68, 2006
Synthesis and characterization of poly(vinyl amine)‐based amphiphilic comb‐like dextran glycopolymers by a two‐step method
Authors: Zhu Junmin , Gosen Christine , Marchant Roger E.
Published: November 2005

Poly(vinyl amine) (PVAm)‐based amphiphilic glycopolymers were synthesized by a two‐step method, that is dextran molecules (Dex, Mw = 1500) were attached to the PVAm backbone by reacting amine groups with dextran lactone, and then, hexanoyl groups (Hex) were attached by reacting the PVAm free amine groups with N‐(hexanoyloxy)succinimide. By adjustment of the feed ratios of Dex/Hex, amphiphilic comb‐like glycopolymers with various hydrophilic and hydrophobic balances were prepared, and their structures were characterized by 1H NMR. Surface activity of the amphiphilic glycopolymers at the air/water interface was demonstrated by reduction in water surface tension. Adsorption of the amphiphilic glycopolymers at the solid/water interface was examined on octadecyltrichlorosilane (OTS)‐coated coverslips by water contact angle measurements. The results show that the amphiphilic glycopolymers need about 20 mol % of dextran attachment to make an effective hydrophilic coating. In comparison with the one‐step reaction by addition of dextran lactone and alkyl succinimide simultaneously, the two‐step approach can attach Dex on PVAm as high as possible in the first step, and offers quantitative advantages in controlling the ratio of hydrophilic and hydrophobic chains along the PVAm backbone, resulting in increased water solubility for the final amphiphilic glycopolymers. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 192–199, 2006
Air‐stable and recoverable catalyst for copper‐catalyzed controlled/living radical polymerization of styrene; In situ generation of Cu(I) species via electron transfer reaction
Authors: Hizal Gurkan , Tunca Umit , Aras Sermin , Mert Humeyra
Published: November 2005

Copper‐catalyzed controlled/living radical polymerization (LRP) of styrene (St) was conducted using the silica gel‐supported CuCl2/N,N,N′,N′,N″‐pentamethyldiethylenetriamine (SG‐CuCl2/PMDETA) complex as catalyst at 110 °C in the presence of a definite amount of air. This novel approach is based on in situ generation and regeneration of Cu(I) via electron transfer reaction between phenols and Cu(II). Sodium phenoxide or p‐methoxyphenol was used as a reducing agent of Cu(II) complexes in LRP. The number–average molecular weight, Mn,GPC, increases linearly with monomer conversion and agrees well with the theoretical values up to 85% conversion The molecular weight distribution, Mw/Mn, decreases as the conversion increases and reaches values below 1.2. The catalyst was recovered in aerobic condition and reused in copper‐catalyzed LRP of St. For the second run, the number–average molecular weights increased with monomer conversion and the polydispersities decreased as the polymerization proceeded and reached to the value <1.3 at 81% conversion. The recycled catalyst retained 90% of its original activity in the subsequent polymerization. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 77–87, 2006
Synthesis and liquid crystalline properties of new amide‐modified poly(1,4‐cyclohexanedimethylene terephthalate)
Authors: Deepa P. , Divya K. , Jayakannan M.
Published: November 2005

New series of cycloaliphatic poly(ester‐amide)s, poly(1,4‐cyclohexanedimethyleneterephthalate‐co‐1,3‐cyclohexanedimethylene terephthalamide), were synthesized through solution polymerization route. The compositions of ester/amide units in the copolymers were varied from 0 to 100% by varying the amount of 1,4‐cyclohexanedimethanol and 1,3‐cyclohexanebis(methylamine) in the feed. The structures of the polymers were confirmed by NMR and FTIR, and the molecular weights were determined by inherent viscosity. The composition analysis by NMR reveals that the reactivity of the diamine toward the acid chlorides is lowered than that of diol, which results in the formation of more ester content in the poly (ester‐amides). The thermal analysis indicate that the new poly(ester‐amide)s having less than 10 mol % of amide linkages are thermotropic liquid crystalline from 200 to 250 °C and a thread like nematic phases are observed under the polarizing microscope. WXRD studies suggest that the liquid crystalline domains promote the nucleation process in the polyester chains and increases the percent crystallinity of the poly(ester‐amide)s. The glass transition temperature of the copolymers initially increases with increase in amide units because of the presence of nematic phases and subsequently follows the Flory–Fox behavior. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 42–52, 2006
Photoactive, liquid‐crystalline, hyperbranched benzylidene polyesters: Synthesis and characterization
Authors: Murali M. , Samui A. B.
Published: November 2005

A novel photoactive, liquid‐crystalline, hyperbranched benzylidene polyester (PAHBP) was synthesized from a dilute solution of an A2 photoactive monomer [bis(4‐hydroxybenzylidene)‐4‐phenyl cyclohexanone] and a B3 monomer (1,3,5‐benzene tricarboxylic acid chloride) by the solution polycondensation method in the presence of pyridine as a condensing agent. PAHBP was thoroughly characterized by Fourier transform infrared, 1H and 13C NMR, ultraviolet–visible spectrometry, and gel permeation chromatography. The inherent viscosity of the polymer was 0.35 dL/g in tetrahydrofuran. The degree of branching was 0.53, which confirmed the branched architecture of the polymer. Furthermore, thermogravimetric analysis, differential scanning calorimetry, and polarized optical microscopy were used to examine the thermal stability and thermotropic liquid‐crystalline properties of the hyperbranched polyester. The polymer exhibited a nematic mesophase over a wide range of temperatures. The photoreactivity of PAHBP was studied by photolysis under ultraviolet light. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 53–61, 2006
Polymerization of cyclopentadiene initiated by methylaluminoxane
Authors: Zhang Dongheng , Sun Wen‐Hua , Hou Junxian , Jie Suyun , Chang Fei
Published: November 2005

The polymerization of cyclopentadiene (CPD) was effectively initiated by methylaluminoxane (MAO) to generate poly(cyclopentadiene) (polyCPD). The effects on the polymerization of some reaction parameters such as the monomer concentration, the initiator concentration, and solvents were investigated. The conversion of CPD was monitored with gas chromatography to investigate the reaction kinetics. The polymerization rate was proportional to the concentrations of MAO in the first order and of the CPD monomer in the second order, and a reasonable cationic polymerization mechanism was suggested on the basis of the kinetic study. PolyCPD obtained at a low temperature could be dissolved in toluene or chloroform, and this indicated lower cross‐coupling during the polymerization reaction. 1H NMR and IR analysis of the polymer indicated that there were almost equal amounts of 1,2‐enchainment and 1,4‐enchainment in the polymer chain. The measurement of polyCPD showed its unique properties as a potential candidate for stable wrappings or electronic packaging materials. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 264–272, 2006
Intricate relation between the content and interactive roles of β‐cyclodextrin in fixing the characteristics of conducting polyaniline composites
Authors: Anitha G. , Subramanian E.
Published: November 2005

This work is an investigation of the influence of β‐cyclodextrin (CD) on the synthesis and characteristics of conducting polyaniline composites (PCDs). In a systematic way, this influence was studied with two different approaches for five PCDs: (1) increasing the initial CD content under identical preparation conditions (three composites: PCD1, PCD2, and PCD3) and (2) using the same initial CD content (as in PCD2) under different preparation conditions (two composites: PCD4 and PCD5). The quite unexpected order of the electrical conductivity (PCD2 < PCD3 < PCD1 < PCD4 < PCD5), the IR and ultraviolet–visible spectroscopy features, and the scanning electron microscopy characteristics (the particle size decreased from PCD1 to PCD3 but increased for PCD4 and PCD5) all exposed and confirmed the markedly different physicochemical characteristics associated with the two groups of composites. PCD5 remained unique among the five (prepared in i‐PrOH–H2O–acid; the other four were prepared in H2O–acid). Differences in the characteristics existed within the group also. The development of all these characteristics in an unrelated order was found to originate from the amount of CD in its two roles as encapsule and dopant toward polyaniline. The interrelation between the content and roles of CD was, however, intricate in combination with the experimental conditions employed. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 281–294, 2006
Behavior of nitroxyl radical in the polymerization process forming copolymers bearing diarylnitrone pendants and photocontrol of refractive indices for these copolymers
Authors: Tanaka Kenta , Takayanagi Emi , Igarashi Tetsutaro , Sakurai Tadamitsu
Published: November 2005

To establish the reaction condition under which the radical copolymerization of methyl methacrylate (MMA) with α‐(2‐hydroxy‐4‐methacryloyloxyphenyl)‐N‐(2,6‐dimethylphenyl)nitrone (HMDN) proceeds smoothly to give photoreactive copolymers, the effects of the nitrone chromophore on the extent to which the radical polymerization of MMA is inhibited were investigated. It was found that the reversible addition of initiating radical to the CHN+(O−) moiety in the nitrone chromophore readily occurs to give the nitroxyl radical. It was also found that the latter radical undergoes an efficient coupling reaction with propagating radical to inhibit the radical copolymerization of MMA with HMDN. However, on raising the reaction temperature and the radical concentration, the copolymerization was successfully carried out. This polymerization condition allowed us to prepare the HMDN/MMA, HMDN/styrene, and HMDN/cyclohexyl acrylate copolymers in good yields. The photoirradiation of the copolymer film prepared on a silicon wafer lowered its refractive index by 0.003–0.023, depending on the relative composition of the diarylnitrone chromophore in these copolymers. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 88–97, 2006
Synthesis and luminescence characteristics of conjugated dendrimers with 2,4,6‐triaryl‐1,3,5‐triazine periphery
Authors: Kim Chae Kyu , Song Eun Seok , Kim Hyung Joo , Park Chiyoung , Kim Young Chul , Kim Jai Kyeong , Yu Jae Woong , Kim Chulhee
Published: November 2005

We have synthesized conjugated dendrimer with triazine peripheries, and their luminescence properties were investigated. The dendrimers consist of dendritic triazine wedges for electron transport, distyrylbenzene core as an emitting moiety, and t‐butyl peripheral groups for good processing properties. The dendrimers have LUMO values of about −2.7 eV possibly because of the triazine moiety with high electron affinity. Photoluminescence study indicates that energy transfer occurs from the triazine wedges to the stilbene bridge, and finally to the core chromophore units due to a cascade decrease of bandgap from the peripheral wedge to core moiety. Therefore, the emission wavelength was determined by the structure of the core unit. The energy transfer efficiency of distyrylbenzene‐cored dendrimers was about 75 and 55% for Trz‐1GD‐DSB and Trz‐2GD‐DSB, respectively. A preliminary electroluminescence property also was investigated. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 254–263, 2006
Improved EL efficiency of fluorene‐thieno[3,2‐b]thiophene‐based conjugated copolymers with hole‐transporting or electron‐transporting units in the main chain
Authors: Lim Eunhee , Jung Byung‐Jun , Shim Hong‐Ku
Published: November 2005

New electroluminescent polymers (poly(9,9′‐dioctylfluorene‐co‐thieno[3,2‐b]thiophene‐co‐benzo[2,3,5]thiadiazole) (P1) and poly(9,9′‐dioctylfluorene‐co‐thieno[3,2‐b]thiophene‐co‐benzo[2,3,5]thiadiazole‐co‐[4‐(2‐ethylhexyloxyl)phenyl]diphenylamine (P2)) possess hole‐transporting or electron‐transporting units or both in the main chains. Electron‐deficient benzothiadiazole and electron‐rich triphenylamine moieties were incorporated into the polymer backbone to improve the electron‐transporting and hole‐transporting characteristics, respectively. P1 and P2 show greater solubility than poly(9,9′‐dioctylfluorene‐co‐thieno[3,2‐b]thiophene (PFTT), without sacrificing their good thermal stability. Moreover, owing to the incorporation of the electron‐deficient benzothiadiazole unit, P1 and P2 exhibit remarkably lower LUMO levels than PFTT, and thus, it should facilitate the electron injection into the polymer layer from the cathode electrode. Consequently, because of the balance of charge mobility, LED devices based on P1 and P2 exhibit greater brightness and efficiency (up to 3000 cd/m2 and 1.35 cd/A) than devices that use the pristine PFTT. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 243–253, 2006
Formation of elastomeric network polymers from ambient heterogeneous hydrosilations of carboranylenesiloxane and branched siloxane monomers
Authors: Kolel‐Veetil Manoj K. , Keller Teddy M.
Published: November 2005

The Karstedt catalyst‐catalyzed ambient‐condition hydrosilation reactions in hexane of a monomeric vinyl‐containing carboranylenesiloxane, 1, and three‐branched siloxane crosslinker monomers were discovered to produce elastomeric network polymers at very rapid rates of formation. The flexible and transparent films of the saturated elastomeric network polymers were observed to possess low glass‐transition temperatures (below −35 °C). Similar hydrosilation reactions at two different reactant ratios involving a diethynyl‐containing carboranylenesiloxane, 2, and the siloxane crosslinkers produced partially hydrosilated and completely hydrosilated polymeric networked systems, which were transparent and elastomeric at room temperature. The glass‐transition temperatures of all the polymeric systems formulated from 2 were below 0 °C. The elastomeric polymeric networks from 1 and 2 were found to have degradation temperatures in the range of 500–550 °C. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 147–155, 2006
Acrylic polymer/silica hybrids prepared by emulsifier‐free emulsion polymerization and the sol–gel process
Authors: Tamai Toshiyuki , Watanabe Mitsuru
Published: November 2005

Acrylic polymer/silica hybrids were prepared by emulsifier‐free emulsion polymerization and the sol–gel process. Acrylic polymer emulsions containing triethoxysilyl groups were synthesized by emulsifier‐free batch emulsion polymerization. The acrylic polymer/silica hybrid films prepared from the acrylic polymer emulsions and tetraethoxysilane (TEOS) were transparent and solvent‐resistant. Atomic force microscopy studies of the hybrid film surface suggested that the hybrid films did not contain large (e.g., micrometer‐size) silica particles, which could be formed because of the organic–inorganic phase separation. The SiOSi bond formed by the cocondensation of TEOS and the triethoxysilyl groups on the acrylic polymer increased the miscibility between the acrylic polymer component and the silica component in the hybrid films, in which the nanometer‐size silica domains (particles) were dispersed homogeneously in the acrylic polymer component. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 273–280, 2006
Anionic polymerization of 2,7‐di‐t‐butyldibenzofulvene: Synthesis, structure, and photophysical properties of the oligomers with a π‐stacked conformation
Authors: Yade Tohru , Nakano Tamaki
Published: November 2005

2,7‐Di‐t‐butyldibenzofulvene (tBu2DBF), a bulky dibenzofulvene derivative, was polymerized using n‐butyllithium as initiator in tetrahydrofuran at −78 °C and in toluene at 0 °C. tBu2DBF afforded mainly oligomers up to trimer even at [monomer]0/[initiator]0 = 20 ([monomer]0 = 0.2 M) at −78 °C and 0 °C, indicating that this monomer is much less reactive than dibenzofulvene (DBF), its parent compound. The reaction at the same [monomer]0/[initiator]0 ratio at an elevated [monomer]0 gave a small amount of insoluble polymer. The oligomers indicated a hypochromic effect in the absorption spectra and only monomer emission in the fluorescent spectra. The conformation of the trimer and the dimer was examined by means of NOESY NMR spectra and semiempirical calculations. In the trimer conformation, the fluorene moieties of the central and the initiation‐side monomeric units were found to be closely stacked on top of each other, while the termination‐side monomeric unit appeared to be in a faster conformational dynamics compared with the other monomeric units. Although the dimer seemed to have a relatively flexible conformation, a π‐stacked structure appeared to be involved in the conformational dynamics to show hypochromicity. The results of this study suggest that the reported intramolecular excited dimer (excimer) formation of the poly‐ and oligo(DBF)s [J Am Chem Soc 2003, 125, 15474] is based on a slight, local conformational change upon photo absorption, leading to a closer π‐stacked alignment of two neighboring fluorene units than that in the ground state. Such a local conformational transition may be difficult for the tBu2DBF trimer because of steric repulsion of the t‐butyl groups. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 561–572, 2006
Synthesis and characterizations of well‐defined branched polymers with AB2 branches by combination of RAFT polymerization and ROP as well as ATRP
Authors: Luan Bin , Zhang Bao‐Qing , Pan Cai‐Yuan
Published: November 2005

A well‐defined branched copolymer with PLLA‐b‐PS2 branches was prepared by combination of reversible addition‐fragmentation transfer (RAFT) polymerization, ring‐opening polymerization (ROP), and atom transfer radical polymerization (ATRP). The RAFT copolymerization of methyl acrylate (MA) and hydroxyethyl acrylate (HEA) yielded poly(MA‐co‐HEA), which was used as macro initiator in the successive ROP polymerization of LLA. After divergent reaction of poly(MA‐co‐HEA)‐g‐PLLAOH with divergent agent, the macro initiator, poly(MA‐co‐HEA)‐g‐PLLABr2 was formed in high conversion. The following ATRP of styrene (St) produced the target polymer, poly(MA‐co‐HEA)‐g‐(PLLA‐b‐PS2). The structures, molecular weight, and molecular weight distribution of the intermediates and the target polymers obtained from every step were confirmed by their 1H NMR and GPC measurements. DSC results show one T = 3 °C for the poly(MA‐co‐HEA), T = −5 °C, T= 122 °C, and T = 157 °C for the branched copolymers (poly(MA‐co‐HEA)‐g‐PLLA), and T = 51 °C, T = 116 °C, and T = 162 °C for poly(MA‐co‐HEA)‐g‐(PLLA‐b‐PS2). © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 549–560, 2006
Singlewall carbon nanotubes covered with polystyrene nanoparticles by in‐situ miniemulsion polymerization
Authors: Ham Hyeong Taek , Choi Yeong Suk , Chee Mu Guen , Chung In Jae
Published: November 2005

This work is to make carbon nanotubes dispersible in both water and organic solvents without oxidation and cutting nanotube threads. Polystyrene‐singlewall carbon nanotube (PS‐SWNT) composites were prepared with three different methods: miniemulsion polymerization, conventional emulsion polymerization, and mixing SWNT with PS latex. The two factors, crosslinking and surface coverage of PS are important factors for the mechanical and electrical properties, including dispersion states of SWNT in various solvents. The PS‐SWNT composite prepared via a conventional emulsion polymerization showed SWNT bundles entirely covered with PS, whereas the PS‐SWNT composite prepared via a miniemulsion polymerization showed SWNT partially covered with crosslinked PS nanoparticles. The method of mixing SWNTs with PS latex did not show the well dispersed state of carbon nanotubes because PS was not crosslinked and was dissolved in a solvent, and nanotubes separated from PS precipitated. So the PS nanoparticle‐SWNT composite had lower electrical resistance, and higher mechanical strength than the other composites made by the latter two methods. As the amount of SWNT increases, the bare surface area of SWNT increases and the electrical conductivity increases in the composite made by the miniemulsion polymerization. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 573–584, 2006
Grafting of silica during the processing of silica‐filled SBR: Comparison between length and content of the silane
Authors: Ramier J. , Chazeau L. , Gauthier C. , Guy L. , Bouchereau M. N.
Published: November 2005

The treatment of nanoscopic silica grafted in the blend during the processing of silica‐filled styrene butadiene rubber was performed with silane, introduced at different concentrations, or at a constant concentration with a given length of alkyl chain. From swelling measurements in water and in solvent, the maximum silane content that can be grafted has been calculated as a function of the length of the silane alkyl chains as well as their efficiency to cover the silica surface. The found values are close to the values found in the literature for grafting in solution. Moreover, a direct correspondence between the length of the silane alkyl chains and their concentration has been deduced. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 143–152, 2006
Synthesis and characterization of polyaniline–polyamidoamine dendrimer blends
Authors: Chao C. M. , Wang G. P. , Wu K. H. , Chang T. C.
Published: November 2005

A novel conductive blend of polyaniline (PANI) with polyamidoamine dendrimer (PAMAM (G 2.0)) was prepared by different blending procedure. The PANI‐PAMAM blended polymers were characterized by UV–vis, FTIR, and electron paramagnetic resonance (EPR) spectra. The effect of varying the blending procedure on structure and EPR properties of PANI‐PAMAM blended polymers was investigated. Varying the blending procedure and temperature has a direct effect on the structure and EPR parameters (ΔHPP, g factor, NS, T2, and A/B ratio). EPR spectroscopic studies suggested the presence of chemical interaction between PANI and PAMAM. Electron localization effects in PANI‐PAMAM blended polymers can therefore be studied using the technique of EPR. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1–8, 2006
Surface and interface morphology of polystyrene/poly(methyl methacrylate) thin‐film blends and bilayers
Authors: Li Yanxia , Yang Yuming , Yu Fusheng , Dong Lisong
Published: November 2005

The surface and interface morphologies of polystyrene (PS)/poly(methyl methacrylate) (PMMA) thin‐film blends and bilayers were investigated by means of atomic force microscopy (AFM) and X‐ray photoelectron spectroscopy. Spin‐coating a drop of a PS solution directly onto a PMMA bottom layer from a common solvent for both polymers yielded lateral domains that exhibited a well‐defined topographical structure. Two common solvents were used in this study. The structure of the films changed progressively as the concentration of the PS solution was varied. The formation of the blend morphology could be explained by the difference in the solubility of the two polymers in the solvent and the dewetting of PS‐rich domains from the PMMA‐rich phase. Films of the PS/PMMA blend and bilayer were annealed at temperatures above their glass‐transition temperatures for up to 70 h. All samples investigated with AFM were covered with PS droplets of various size distributions. Moreover, we investigated the evolution of the annealed PS/PMMA thin‐film blend and bilayer and gave a proper explanation for the formation of a relatively complicated interface inside a larger PS droplet. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 9–21, 2006
Compatibility characterization of poly(lactic acid)/poly(propylene carbonate) blends
Authors: Ma Xiaofei , Yu Jiugao , Wang Ning
Published: November 2005

The compatibility of poly(lactic acid) (PLA)/poly(propylene carbonate) (PPC) blends was investigated with Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and tensile testing. The PLA/PPC blends were prepared over the whole composition range. FTIR spectroscopy revealed that there were several specific interactions between the chains of PLA and PPC: the interaction between CH and OC and CO···OC or CO···OC dipole–dipole interactions. Moreover, PLA and PPC were compatible. DSC indicated that PLA and PPC were partially miscible but compatible to some extent because of the similar chemical natures of the blend components. TGA showed that the compatibility of PLA and PPC enhanced the thermal stability of PPC in the blends. As calculated by the Horowitz–Metzger equation, the activation energy for decomposition (Et) of PPC in PLA/PPC (70/30) was 200.6 kJ/mol, whereas Et of pure PPC was only 56.0 kJ/mol. A study of the mechanical properties versus the composition and the strain versus the stress illustrated that there was good compatibility between PLA and PPC, and the phase inversion of the PLA/PPC system occurred between 70 and 60 wt % PLA in the PLA/PPC blends. The Pukanszky model gave credit to very strong interfacial adhesion between PLA and PPC. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 94–101, 2006
Modification of a hydrophilic linear polyurethane by crosslinking with a polydimethylsiloxane. Influence of the crosslink density and of the hydrophobic/hydrophilic balance on the water transport properties
Authors: Dolmaire N. , Méchin F. , Espuche E. , Pascault J. P.
Published: November 2005

A hydrophilic thermoplastic polyurethane (TPU) was modified by reactive extrusion to obtain in a first step a grafted and soluble material and to finally form by a hydrolysis condensation process a weakly crosslinked network. Different isocyanates were used as grafting agents and a α,ω‐dihydroxypoly(dimethylsiloxane) (PDMS) was used to modify the hydrophilic/hydrophobic balance of the material and the chain length between the crosslinks. The influence of the isocyanate functionality and of the PDMS content were studied on the network formation and on the thermomechanical and water sorption properties. The networks properties were also compared with those of a TPU/PDMS blend. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 48–61, 2006
Thermal memory of poly(3‐hydroxybutyrate) using temperature‐modulated differential scanning calorimetry
Authors: Gunaratne L. M. W. K. , Shanks R. A.
Published: November 2005

The influence of thermal history on morphology, melting, and crystallization behavior of bacterial poly(3‐hydroxybutyrate) (PHB) has been investigated using temperature‐modulated DSC (TMDSC), wide‐angle X‐ray diffraction (WAXRD) and polarized optical microscopy (POM). Various thermal histories were imparted by crystallization with continuous and different modulated cooling programs that involved isoscan and cool–heat segments. The subsequent melting behavior revealed that PHB experienced secondary crystallization during heating and the extent of secondary crystallization varied with the cooling treatment. PHB crystallized under slow, continuous, and moderate cooling rates were found to exhibit double melting behavior due to melting of TMDSC scan‐induced secondary crystals. PHB underwent considerable secondary crystallization/annealing that took place under modulated cooling conditions. The overall melting behavior was interpreted in terms of recrystallization and/or annealing of crystals. Interestingly, the PHB analyzed by temperature modulation programs showed a broad exotherm before the melting peak in the nonreversing heat capacity curve and a multiple melting reversing curve, verifying that the melting–recrystallization and remelting process was operative. WAXRD and POM studies supported the correlations from DSC and TMDSC results. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 70–78, 2006
Quantum‐chemical approach to the solvatochromic transition in polysilane derivatives
Authors: Orimoto Yuuichi , Aoki Yuriko
Published: November 2005

We approached the solvatochromic transition observed in polysilane derivatives (poly[bis(4‐propoxybutyl)silylene] (PPBS)) from the standpoint of various quantum chemical treatments. It was found from conventional geometry optimizations at the levels of semiempirical and ab initio molecular orbital methods that a protonation to polysilane oligomers with side chain R = OCH3 results in the conformational change of Si‐backbone to a trans‐zigzag structure. Using the Elongation method, which was developed for efficient calculations of huge systems, it was demonstrated that a protonation could change the conformation of Si‐backbone to a trans‐zigzag structure over 10–14 Si atoms. In addition, ab initio calculations showed that the positive charge of a proton can delocalize into the Si‐backbone through a long side chain in PPBS. Positively charged polysilane oligomers provide a rotational barrier that prefers a trans‐zigzag structure, whereas neutral oligomers have a barrier that results to a random structure. This unique behavior of the charged polysilane oligomers should not be disregarded in understanding the mechanism of the solvatochromic transition in PPBS. In ab initio configuration interaction/Mφller‐Plesset through‐space/bond interaction analysis, it was found that such a unique behavior of the rotational barrier in polysilane oligomers could be explained by the effect of orbital delocalization through σ‐conjugation on the Si‐backbone. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 119–133, 2006