bluuebunny/crossref_metadata_2025 huggingface dataset:
ChemInform Abstract: A Green and Regioselective Acetylation of Thioglycoside with Ethyl Acetate.
Authors: Liang Pi‐Hui , Lu Yin‐Jen , Tang Ting‐Hsuan
Published: March 2011

A simple optimized protocol renders possible the selective conversion of carbohydrates to 6‐monoacetylated derivatives using ethyl acetate.
ChemInform Abstract: Stereoselective Formal Synthesis of (+)‐Allokainic Acid via Thiol‐Mediated Acyl Radical Cyclization.
Authors: Yamada Ken‐ichi , Sato Tomohiro , Hosoi Masaki , Yamamoto Yasutomo , Tomioka Kiyoshi
Published: March 2011

A known intermediate (III) in the synthesis of (+)‐allokainic acid is prepared via a thiol‐mediated radical cyclization of aldehyde (I) as a key step.
ChemInform Abstract: A Simple Synthesis of the Lamellarin Analogues from 3‐Nitro‐2‐trifluoromethyl‐2H‐chromenes and 1‐Benzyl‐3,4‐dihydroisoquinolines.
Authors: Korotaev Vladislav Yu. , Sosnovskikh Vyacheslav Ya. , Yasnova Evgeniya S. , Barkov Alexey Yu. , Shklyaev Yurii V.
Published: March 2011

New CF3‐containing lamellarin analogues (III) (6 examples) are obtained by the Grob reaction of chromenes (II) with dihydropapaverine (Ia) or drotaverine (Ib).
ChemInform Abstract: A New Quinone from Maesa indica (Roxb.) A.DC., (Myrsinaceae).
Authors: Kuruvilla Gina R. , Neeraja M. , Srikrishna A. , Rao G. S. R. Subba , Sudhakar A. V. S. , Venkatasubramanian Padma
Published: March 2011

isolation and structure elucidation of kiritiquinone (I), a new benzoquinone with considerable cytotoxicity
ChemInform Abstract: Design, Synthesis and Antiproliferative Studies of a Novel Series of Indirubin Derivatives.
Authors: Wang Tian Cai , Wei Ju Zhi , Guo Chuan Sheng , Zhang Hui Bin , Fan Hou Xing
Published: March 2011

A series of novel indirubin derivatives (I) is synthesized and evaluated for their antiproliferative activity against various human cancer cell lines.
ChemInform Abstract: Anticonvulsant and Toxicity Evaluation of Newer 4H‐Benzo[1,4]oxazin‐3‐ones: The Effect of Two Hydrogen Bonding Domains.
Authors: Siddiqui Nadeem , Ali Ruhi , Arshad M. Faiz , Ahsan Waquar , Ahmed Sharique , Alam M. Shamsher
Published: March 2011

18 Compounds of type (I) are prepared and tested for their anticonvulsant activities.
ChemInform Abstract: Layered Perovskite‐Like Oxides 0112 Type. Structure, Properties, and Possible Applications
Authors: Klyndyuk Andrei
Published: March 2011

Review: 112 refs.
ChemInform Abstract: Organometallic Routes into the Nanorealms of Binary Fe‐Si Phases
Authors: Kolel‐Veetil Manoj K. , Keller Teddy M.
Published: March 2011

Review: 115 refs.
ChemInform Abstract: Ammonia‐Borane and Related Compounds as Dihydrogen Sources
Authors: Staubitz Anne , Robertson Alasdair P. M. , Manners Ian
Published: March 2011

Review: 320 refs.
ChemInform Abstract: The Organometallic Chemistry of Group 10 Poly(pyrazolyl)borate Complexes
Authors: Crossley Ian R.
Published: March 2011

Review: 173 refs.
ChemInform Abstract: Synthesis of Purine Derivatives as Scaffolds for a Diversity of Biological Activities
Authors: Conejo‐Garcia A. , Cruz‐Lopez O. , Gomez‐Perez V. , Morales F. , Garcia‐Rubino M. E. , Kimatrai M. , Nunez M. C. , Campos J. M.
Published: March 2011

Review: 128 refs.
ChemInform Abstract: Formation of a Three‐Membered Ring
Authors: Tsuno Takashi
Published: March 2011

Review: [ i.e.
ChemInform Abstract: Cross‐Coupling Reactions of Polyfluoroarenes via C—F Activation
Authors: Sun Alex D. , Love Jennifer A.
Published: March 2011

Review: 97 refs.
ChemInform Abstract: Enantioselective, Organocatalytic Morita—Baylis—Hillman and Aza‐Morita—Baylis—Hillman Reactions: Stereochemical Issues
Authors: Mansilla Javier , Saa Jose M.
Published: March 2011

Review: 157 refs.
ChemInform Abstract: Formation of a Five‐Membered Ring
Authors: Pandey Ganesh , Gadre Smita R.
Published: March 2011

Review: 111 refs.
ChemInform Abstract: Solution‐Phase Counterion Effects in Supramolecular and Mechanostereochemical Systems
Authors: Gasa Travis B. , Valente Cory , Stoddart J. Fraser
Published: March 2011

Review: 76 refs.
ChemInform Abstract: Role of Angiontensin Receptors on Remodeling Perivascular Nerves
Authors: Hobara Narumi , Goda Mitsuhiro , Hashikawa Naoya , Jin Xin , Zamami Yoshito , Takatori Shingo , Kawasaki Hiromu
Published: March 2011

Review: 13 refs.
ChemInform Abstract: Self‐Assembled Gels for Biomedical Applications.
Authors: Truong Warren Ty , Su Yingying , Meijer Joris T. , Thordarson Pall , Braet Filip
Published: March 2011

Review: 78 refs
ChemInform Abstract: Melt Electrospinning.
Authors: Hutmacher Dietmar W. , Dalton Paul D.
Published: March 2011

Review: 82 refs.
ChemInform Abstract: An Integrated Computational Protocol for the Accurate Prediction of EPR and PNMR Parameters of Aminoxyl Radicals in Solution
Authors: Barone Vincenzo , Cimino Paola , Pedone Alfonso
Published: March 2011

Review: 60 refs.
ChemInform Abstract: Two‐Photon Fluorescent Probes for Metal Ions.
Authors: Kim Hwan Myung , Cho Bong Rae
Published: March 2011

Review: 61 refs.
CD38 identifies a hypo‐proliferative IL‐13‐secreting CD4+ T‐cell subset that does not fit into existing naive and memory phenotype paradigms
Authors: Scalzo‐Inguanti Karen , Plebanski Magdalena
Published: March 2011

CD38 is commonly regarded as an activation marker for human T cells. Herein, we show that CD38 expression identifies a hypo‐proliferative CD4+ T‐cell subset that, following TCR stimulation, retains expression of naive cell surface markers including CD45RA, CD62L and CCR7. Hypo‐proliferation was mediated by reduced CD25 up‐regulation upon TCR stimulation compared to CD4+CD38− cells and lack of responsiveness to exogenous IL‐2. Instead, CD4+CD38+ T cells expressed CD127, and hypo‐proliferation was reversed by addition of IL‐7, further associated with increased STAT5 phosphorylation. This phenotype was exacerbated by addition of an agonistic CD38‐binding antibody, suggesting that signaling through CD38 promotes this cell profile. Activated CD4+CD38+ cells had a bias towards IL‐13 secretion, but not other Th2 cytokines such as IL‐4 or IL‐5. In comparison, the CD4+CD38− cells had a clear bias towards secretion of Th1‐associated cytokines IFN‐γ and TNF. The existence of such CD4+CD38+ T cells may play an important role in pathologies such as asthma, which are associated with IL‐13, but not IL‐4 and IL‐5. Coupled with responsiveness to IL‐7 but not IL‐2, and the involvement of CD38 ligation, our results highlight a unique T‐cell subpopulation that does not fit into existing naive and memory cell paradigms.
Cyclometallated Palladium Diphosphane Compounds Derived from the Chiral Ligand (S)‐PhCH(Me)NMe2. Michael Addition Reactions to the Vinylidene Double Bond
Authors: Mosteiro Roberto , Fernández Alberto , Vázquez‐García Digna , López‐Torres Margarita , Rodríguez‐Castro Antonio , Gómez‐Blanco Nina , Vila José M. , Fernández Jesús J.
Published: March 2011

Treatment of (S)‐PhCH(Me)NMe2 (1) with palladium(II) acetate in toluene gave the dinuclear cyclometallated complex [Pd{(S)‐C6H4CH(Me)NMe2‐C2,N}(μ‐OAc)]2 (2), inwhich the ligand is bonded to the palladium atom through the nitrogen phenyl carbon atoms. The reaction of 2 with aqueous sodium chloride gave the chloro‐bridged complex 3. The reaction of 3 with (R,R)‐DIOP [(4R,5R)‐4,5‐bis(diphenylphosphanylmethyl)‐2,2‐dimethyl‐1,3‐dioxolane], in a complex/phosphane 1:1 molar ratio, gave [{Pd[(S)‐C6H4CH(Me)NMe2‐C2,N]Cl}2(μ‐(R,R)‐DIOP)] (4). The reaction of 3 with (Ph2P)2C=CH2 (vdpp) in a 1:2 molar ratio in the presence of NH4PF6 or NaClO4 afforded [Pd{(S)‐C6H4CH(Me)NMe2‐C2,N}{(Ph2P)2C=CH2‐P,P′}][Y] [Y = PF6– (5); Y = ClO4– (6), respectively]. The treatment of 5 with acetylacetone in the presence of anhydrous sodium carbonate or with methanol afforded the addition products, [Pd{(S)‐C6H4CH(Me)NMe2‐C2,N}{(Ph2P)2CHCH2R‐P,P′}][PF6] [R = CH(COMe)2 (7); R = OMe (8), respectively], in good yield. The treatment of 6 with methyl acetoacetate and anhydrous sodium carbonate afforded the addition derivative [Pd{(S)C6H4CH(Me)NMe2C2,N}{(Ph2P)2CHCH2CH‐(COMe)(COOMe)‐P,P′}][ClO4] (9). The NMR spectra of the addition products showed that some of the resonances were duplicated due to the existence of optical isomers. The X‐ray crystal structure of complexes 2, 5, and 7 were determined by single‐crystal X‐ray diffraction analysis.
Synthesis, Structural Characterization and Metal Inclusion Properties of 18‐, 20‐ and 22‐Membered Oxaazacyclophanes and Oxaazacalix[4]arene Analogues: Macrocyclic Amine and Schiff Base Receptors with Variable NxOy Donor Sets
Authors: Moreno‐Corral Ramón , Höpfl Herbert , Machi‐Lara Lorena , Lara Karen O.
Published: March 2011

A series of oxaazacyclophanes and oxaazacalix[4]arene analogues with 18‐, 20‐ and 22‐membered rings have been synthesized from diamine and dialdehyde building blocks and structurally characterized by spectroscopic methods. One diamine precursor and four macrocycles have additionally been analysed by single‐crystal X‐ray diffraction. Two of the oxaazacalix[4]arene analogues were employed for metal ion complexation studies based on UV/Vis absorption spectroscopy, showing both compounds to be able to form complexes with Cu2+ and Zn2+.
An Efficient Approach to 2‐Bromoalken‐3‐ols by Regioselective Bromohydroxylation Reaction of Simple Allenes with NBS
Authors: Kong Wangqing , Guo Binjie , Fu Chunling , Ma Shengming
Published: March 2011

A regioselective bromohydroxylation reaction of simple allenes affording 2‐bromoalken‐3‐ols in moderate‐to‐good yields has been developed by using NBS as the electrophilic reagent in a mixture of 1,4‐dioxane/H2O (1:1) at room temperature. Through this study it has been concluded that the regioselectivity is determined by various factors including steric and electronic effects of the substituents of the allene moiety.
Bilateral parotid abscesses as the initial presentation of strongyloidiasis in the immunocompetent host
Authors: Tsai Yao‐Te , Yeh Chi‐Ju , Chen Yen‐An , Chen Yi‐Wei , Huang Shiang‐Fu
Published: March 2011

Background

Most suppurative parotid abscesses are unilateral and result from bacterial infection via Stensen's duct. Formation of bilateral parotid abscesses rarely occur, and cases arising in the setting of parasite infection have not been described to date.

Methods and Results

A 41‐year‐old man presented with bilateral parotid abscesses and underwent incision and drainage of right‐sided swelling because of poor response to the aspiration drainage and intravenous antibiotic therapy. A nematode larva, morphologically consistent with Strongyloides stercoralis (S. stercoralis), was found in the cytologic examination, and bilateral abscesses regressed significantly after administration of Ivermectin.

Conclusion

We report the first case of S. stercoralis infection presenting as bilateral parotid abscesses. This case expands the spectrum of diseases associated with S. stercoralis and suggests that clinicians, especially in the endemic regions, should consider S. stercoralis infection in the differential diagnosis of refractory parotid abscess. © 2011 Wiley Periodicals, Inc. Head Neck, 2012
Airway management before chemoradiation for advanced head and neck cancer
Authors: Langerman Alexander , Patel Riddhi M. , Cohen Ezra E. W. , Blair Elizabeth A. , Stenson Kerstin M.
Published: March 2011

Background

Patients with upper aerodigestive tract tumors can have development of airway compromise both before and during chemoradiotherapy (CRT). Tracheotomy is the classic method for securing a safe airway, but tumor debulking may also be used.

Methods

This was a retrospective review of locoregionally advanced tumors of the base of tongue, larynx, or hypopharynx undergoing CRT between 1995 and 2007.

Results

Forty‐two of the 109 patients presented with signs or symptoms of airway obstruction. Of these, 28 underwent tracheotomy before CRT, and 11 had tumor debulking. Two of the 11 patients who underwent debulking required tracheotomy within 1 year after CRT for persistent edema and fibrosis. Larynx tumors were more likely to require tracheotomy or debulking than other tumors (p = .01).

Conclusions

Debulking is a safe and effective alternative to tracheotomy in select patients with tumor‐related airway obstruction before CRT. Patients who undergo debulking should be monitored closely for recurrence of airway compromise during and after CRT. © 2011 Wiley Periodicals, Inc. Head Neck, 2012
The stable repression of mesenchymal program is required for hepatocyte identity: A novel role for hepatocyte nuclear factor 4α
Authors: Santangelo Laura , Marchetti Alessandra , Cicchini Carla , Conigliaro Alice , Conti Beatrice , Mancone Carmine , Bonzo Jessica A. , Gonzalez Frank J. , Alonzi Tonino , Amicone Laura , Tripodi Marco
Published: March 2011

The concept that cellular terminal differentiation is stably maintained once development is complete has been questioned by numerous observations showing that differentiated epithelium may undergo an epithelial-to-mesenchymal transition (EMT) program. EMT and the reverse process, mesenchymal-to-epithelial transition (MET), are typical events of development, tissue repair, and tumor progression. In this study, we aimed to clarify the molecular mechanisms underlying these phenotypic conversions in hepatocytes. Hepatocyte nuclear factor 4α (HNF4α) was overexpressed in different hepatocyte cell lines and the resulting gene expression profile was determined by real-time quantitative polymerase chain reaction. HNF4α recruitment on promoters of both mesenchymal and EMT regulator genes was determined by way of electrophoretic mobility shift assay and chromatin immunoprecipitation. The effect of HNF4α depletion was assessed in silenced cells and in the context of the whole liver of HNF4 knockout animals. Our results identified key EMT regulators and mesenchymal genes as new targets of HNF4α. HNF4α, in cooperation with its target HNF1α, directly inhibits transcription of the EMT master regulatory genes Snail, Slug, and HMGA2 and of several mesenchymal markers. HNF4α-mediated repression of EMT genes induces MET in hepatomas, and its silencing triggers the mesenchymal program in differentiated hepatocytes both in cell culture and in the whole liver.

Conclusion:

The pivotal role of HNF4α in the induction and maintenance of hepatocyte differentiation should also be ascribed to its capacity to continuously repress the mesenchymal program; thus, both HNF4α activator and repressor functions are necessary for the identity of hepatocytes. (HEPATOLOGY 2011;)
Quantification of volatile compounds in Chinese soy sauce aroma type liquor by stir bar sorptive extraction and gas chromatography–mass spectrometry
Authors: Fan Wenlai , Shen Haiyue , Xu Yan
Published: March 2011

BACKGROUND: Considering the important of aroma compounds on the quality of baijiu, stir bar sorptive extraction (SBSE) coupled with gas chromatography–mass spectrometry was applied to the aromas analysis of baijiu (Chinese liquor).

RESULTS: Based on the results of optimization, a total of 76 volatile compounds were identified from 14 Chinese liquors, including 25 esters, 10 alcohols, 9 aldehydes and ketones, 8 aromatic compounds, 5 furans, 3 nitrogen‐containing compounds, 6 acids, 4 phenols, 3 terpenes, 1 sulfide‐containing compound, 1 lactone, and 1 acetal. By principal component analysis based on quantification results, 14 Chinese liquor samples could be classified into three groups.

CONCLUSION: SBSE is a fast, simple, effective, and reliable method for extracting volatile compounds from Chinese liquor. The chemometrics approach revealed that LJ liquor with soy sauce aroma could exhibit more prominent sauce flavor through extending the time of storage, and its peculiar manufacturing practice was responsible for the soy sauce flavor. Copyright © 2011 Society of Chemical Industry
Changes in pH, acids, sugars and other quality parameters during extended vine holding of ripe processing tomatoes
Authors: Anthon Gordon E , LeStrange Michelle , Barrett Diane M
Published: March 2011

BACKGROUND: Two important quality attributes of processing tomatoes are pH and titratable acidity. These and other quality attributes can be affected by tomato fruit maturity and over‐maturity. We have determined the magnitude of these maturity effects in four processing tomato cultivars commonly grown in California.

RESULTS: Allowing tomatoes to remain on the vine for up to 4 weeks after ripening resulted in an increase in fruit pH of between 0.01 and 0.02 unit per day for the four cultivars examined. The increase in pH was paralleled by a decrease in titratable acidity, due to a loss of citric acid. Glucose and fructose concentrations also declined with increasing maturity after ripening. Other quality parameters (color, lycopene, total pectin, pectin solubility, and Bostwick consistency) all showed little change.

CONCLUSION: Vine holding of ripe fruit adversely affects quality, especially pH and titratable acidity. Recent problems with high tomato juice pH encountered by tomato processors in California could be the result of increased average fruit maturity at harvest. Copyright © 2011 Society of Chemical Industry
Critical care issues in patients after liver transplantation
Authors: Razonable Raymund R. , Findlay James Y. , O'Riordan Aisling , Burroughs Gordon S. , Ghobrial Mark R. , Agarwal Banwari , Davenport Andrew , Gropper Michael
Published: March 2011

The majority of patients who undergo liver transplantation (LT) spend some time in the intensive care unit during the postoperative period. For some, this is an expected part of the immediate posttransplant recovery period, whereas for others, the stay is more prolonged because of preexisting conditions, intraoperative events, or postoperative complications. In this review, 4 topics that are particularly relevant to the postoperative intensive care of LT recipients are discussed, with an emphasis on current knowledge specific to this patient group. Infectious complications are the most common causes of early posttransplant morbidity and mortality. The common patterns of infection seen in patients after LT and their management are discussed. Acute kidney injury and renal failure are common in post-LT patients. Kidney injury identification, etiologies, and risk factors and approaches to management are reviewed. The majority of patients will require weaning from mechanical ventilation in the immediate postoperative period; the approach to this is discussed along with the approach for those patients who require a prolonged period of mechanical ventilation. A poorly functioning graft requires prompt identification and appropriate management if the outcomes are to be optimized. The causes of poor graft function are systematically reviewed, and the management of these grafts is discussed. Liver Transpl 17:511-527, 2011. © 2011 AASLD.
Lack of a Correlation Between Portal Vein Flow and Pressure
Authors: Sainz-Barriga Mauricio , Scudeller Luigia , Costa Maria Gabriella , de Hemptinne Bernard , Troisi Roberto Ivan
Published: March 2011

The portal vein flow (PVF), portal vein pressure (PVP), and hepatic venous pressure gradient (HVPG) were prospectively assessed to explore their relationships and to better define hyperflow and portal hypertension (PHT) during liver transplantation (LT). Eighty-one LT procedures were analyzed. No correlation between PVF and PVP was observed. Increases in the central venous pressure (CVP) were transmitted to the PVP (58%, range = 25%-91%, P = 0.001). Severe PHT (HVPG ≥ 15 mm Hg) showed a significant reciprocal association with high PVF (P = 0.023) and lower graft survival (P = 0.04). According to this initial experience, an HVPG value ≥ 15 mm Hg is a promising tool for the evaluation of hemodynamic stress potentially influencing outcomes. An algorithm for graft inflow modulation based on flows, gradients, and systemic hemodynamics is provided. In conclusion, the evaluation of PHT severity with PVP could be delusive because of the influence of CVP. PVF and PVP do not correlate and should not be used individually to assess hyperflow and PHT during LT. Liver Transpl 17:836-848, 2011. © 2011 AASLD.
BSA Adsorption on Differently Charged Polystyrene Nanoparticles using Isothermal Titration Calorimetry and the Influence on Cellular Uptake
Authors: Baier Grit , Costa Cristiane , Zeller Anke , Baumann Daniela , Sayer Claudia , Araujo Pedro H. H. , Mailänder Volker , Musyanovych Anna , Landfester Katharina
Published: March 2011

BSA adsorption onto negatively and positively charged polystyrene nanoparticles was investigated. The nanoparticles were characterized in terms of particle size, zeta potential, surface group density, and morphology. The adsorption behavior of BSA on the particle surface, as a function of pH and overall charge of the particle, was studied using ITC. Different thermodynamic data such as enthalpy changes upon binding and stoichiometry of the systems were determined and discussed. The degree of surface coverage with BSA was calculated using the thermodynamic data. The cellular uptake of particles before and after BSA adsorption was studied using HeLa cells in the presence and absence of supplemented FCS in the cell culture medium.

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Annihilation Upconversion in Cells by Embedding the Dye System in Polymeric Nanocapsules
Authors: Wohnhaas Christian , Turshatov Andrey , Mailänder Volker , Lorenz Steffen , Baluschev Stanislav , Miteva Tzenka , Landfester Katharina
Published: March 2011

The first energetically conjoined TTA‐assisted photon energy upconversion operating in cell tissue is described. The synthesized nanocapsules with the encapsulated UC dye system consisting of an emitter and a sensitizer show very efficient UC emission in aqueous dispersion under extremely low excitation intensity down to 0.05 W · cm−2 so that tissue and cells are not affected by the excitation light. The demonstrated sub‐linear intensity dependence of the UC emission is of crucial importance for life‐science applications as the UC photon could serve as a local or in situ optical excitation source for subsequent light‐triggered processes.

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Amphiphilic Polysaccharide Nanogels as Artificial Chaperones in Cell‐Free Protein Synthesis
Authors: Sasaki Yoshihiro , Asayama Wakiko , Niwa Tatsuya , Sawada Shin‐ichi , Ueda Takuya , Taguchi Hideki , Akiyoshi Kazunari
Published: March 2011

Cell‐free protein synthesis is a promising technique for the rapid production of proteins. However, the application of the cell‐free systems requires the development of an artificial chaperone that prevents aggregation of the protein and supports its correct folding. Here, nanogel‐based artificial chaperones are introduced that improve the folding efficiency of rhodanese produced in cell‐free systems. Although rhodanese suffers from rapid aggregation, rhodanese was successfully expressed in the presence of the nanogel and folded to the enzymatically active form after addition of cyclodextrin. To validate the general applicability, the cell‐free synthesis of ten water‐soluble proteins was examined. It is concluded that the nanogel enables efficient expression of proteins with strong aggregation tendency.

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Highly Efficient Intracellular Drug Delivery with a Negatively Charged Hyperbranched Polysulfonamine
Authors: Chen Suyun , Tan Zhonghua , Li Nan , Wang Ruibin , He Lin , Shi Yunfeng , Jiang Lei , Li Peiyong , Zhu Xinyuan
Published: March 2011

Efficient intracellular translocation is achieved using an easily prepared hyperbranched polysulfonamine that remains negatively charged at physiological pH. Investigations on the cellular uptake mechanism and the subcellular distribution of PSA are reported. The in vitro cytotoxicity of PSA is found to be low. Using doxorubicin as a model drug, a PSA/drug complex is prepared by electrostatic interaction with a high drug payload that exhibits a controlled release in response to pH. Efficient intracellular drug delivery, strong growth inhibition of tumor cells, and low cytotoxicity to normal cells are observed. The results suggest a possible way to utilize anionic polymers for intracellular delivery of therapeutic moieties or drugs.

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Amphiphilic PEG‐b‐PMCL‐b‐PDMAEMA Triblock Copolymers: From Synthesis to Physico‐Chemistry of Self‐Assembled Structures
Authors: Matter Yves , Enea Ramona , Casse Olivier , Lee Cameron C. , Baryza Jeremy , Meier Wolfgang
Published: March 2011

A synthetic route toward a new family of amphiphilic mPEG‐b‐PMCL‐b‐PDMAEMA triblock copolymers is reported. Chemical structures and compositions are confirmed by 1H NMR and SEC. Polydispersity indices are typically <1.4, indicating good control of the reactions. The physicochemical parameters associated with mPEG‐b‐PMCL‐b‐PDMAEMA self‐assembled structures are investigated. Nanoparticles are prepared via a co‐solvent method, and parameters such as nanoparticle $\overline {M} _{{\rm w}} $, Nagg, A2, and Rh are calculated based on static and dynamic light scattering data. Critical aggregation concentrations for the polymers are determined by measuring surface tensions of polymer solutions. TEM is employed to visualize the morphology of the assemblies.

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In situ Foaming Evolution of Flexible Polyurethane Foam Nanocomposites
Authors: Bernal M. Mar , Lopez‐Manchado Miguel Angel , Verdejo Raquel
Published: March 2011

The effect of both as‐produced and functionalised CNTs on the polymerisation evolution of water‐blown PU foams containing up to 0.3 wt.‐% CNTs was studied by in situ FT‐IR spectroscopy. FT‐IR revealed a decrease on the rate of isocyanate conversion as a function of loading fraction for both as‐grown and oxidised CNTs. This dependency suggested that the isocyanate conversion at the early stages of the reaction was governed by the kinetic effects imposed by the presence of the CNTs. The onset of microphase separation was accelerated by the addition of functionalised CNTs (f‐CNTs) but not by as‐produced CNTs due to the different surface functionalities. Measurements of the foaming viscoelastic properties showed an increase on the storage modulus with the CNT content, which indicated the reinforcement of the foam.

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Effect of Maleated Compatibilizer on Performance of PLA/Wheat Straw‐Based Green Composites
Authors: Nyambo Calistor , Mohanty Amar K. , Misra Manjusri
Published: March 2011

In this study, the use of PLA‐g‐MA is investigated as a potential method for improving interfacial adhesion between agricultural residues and PLA, with the goal of enhancing mechanical properties. Compatibilization was achieved by using PLA‐g‐MA prepared via reactive extrusion. Green renewable and compatibilized PLA/wheat straw composites were extruded and injection‐molded. Addition of 3 and 5 phr PLA‐g‐MA to the composites resulted in significant improvements in tensile strength (20%) and flexural strength (14%) of the composites, matching that of the neat polymer. The observed improvement in strength was attributed to the good interfacial adhesion between the fiber and matrix.

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Continuous Controlled Radical Polymerization of Methyl Acrylate in a Copper Tubular Reactor
Authors: Chan Nicky , Cunningham Michael F. , Hutchinson Robin A.
Published: March 2011

The use of copper tubing as both the reactor and as a catalyst source is demonstrated for continuous controlled radical polymerization of methyl acrylate at ambient temperature and at low solvent content of 30%. The high surface area provided by the copper walls mediates the reaction via the single electron transfer–living radical polymerization (SET‐LRP) mechanism. The polymerizations proceeded quickly, reaching 67% conversion at a residence time of 16 min. Ligand concentration could also be reduced without a sharp drop in polymerization rate, demonstrating the potential for decreased raw material and post‐process purification costs. Chain extension experiments conducted using synthesized polymer showed high livingness. The combination of living polymer produced at high polymerization rates at ambient temperature and low volatile organic solvent content demonstrate the potential of a copper reactor for scale up of SET‐LRP.

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“Clip” and “Click” Chemistries Combination: Toward Easy PEGylation of Degradable Aliphatic Polyesters
Authors: Freichels Hélène , Pourcelle Vincent , Le Duff Cécile S. , Marchand‐Brynaert Jacqueline , Jérôme Christine
Published: March 2011

α‐Methoxy‐ω‐alkyne poly(ethylene glycol) (PEG) was tagged with pendent N‐hydroxy‐succinimidyl activated esters by photografting of a molecular clip. This easily synthesized heterofunctional PEG was found to be a versatile building block for (i) conjugation with an amino derivative and (ii) grafting to azido functional aliphatic polyesters backbone by Huisgen's 1,3‐dipolar cycloaddition. This original combination of “clip” and “click” reactions provides a versatile and straightforward pathway for the synthesis of functional amphiphilic and degradable copolymers valuable for biomedical applications such as in drug‐delivery.

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Highly Selective Colorimetric and Fluorometric Probes for Fluoride Ions Based on Nitrobenzofurazan‐containing Polymers
Authors: Hu Jinming , Li Changhua , Cui Yue , Liu Shiyong
Published: March 2011

We report on a novel colorimetric and fluorometric chemosensor for fluoride ions based on 4‐(2‐acryloyloxyethylamino)‐7‐nitro‐2,1,3‐benzoxadiazole (NBDAE)‐labeled polymers. Upon gradual addition of fluoride ions (F–), the green fluorescence emission of NBDAE moieties can be dramatically quenched, accompanied with the distinct colorimetric transition from green to yellow. NBDAE moieties are capable of selectively recognizing F– ions via hydrogen‐bonding (H‐bonds) interactions at low F– concentration and subjected to further deprotonation process at high F– concentration. NBDAE‐labeled polymers in organic solvents possess high selectivity and fluorescence “turn‐off” characteristics toward the sensing of F– ions with the detection limit down to ≈0.8 µM.

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Influencing the morphology of polymer blends through graft copolymers
Authors: Braun D. , Fischer M. , Hellmann G.P.
Published: March 2011

Graft copolymers have a potential as compatibilizers in two‐component thermoplastic polymer blends, and also as impact‐modifiers in one‐component thermoplastics. The compatibility of the blocks of the copolymer (i.e. the grafts and the main chain) with the chains of the matrix polymers must be adjusted carefully. Blends of various polymers, especially of polystyrene (PS) and poly(vinyl chloride) (PVC), with graft copolymers on the basis of polybutadiene are discussed. An excellent compatibilizer, for blends PS/PVC, is a block‐graft copolymer, derived from a diblock copolymer of Styrene and butadiene, with grafts of cyclohexyl methacrylate monomelic units.
Physical ageing of heterogeneous polymers
Authors: Maurer Frans H.J.
Published: March 2011

Physical ageing has a pronounced effect on the short term and long term viscoelastic behaviour of polymers. The Kohlrausch‐Williams‐Watts (KWW) equation has been used extensively to describe the relaxation behaviour of thermorheologically simple amorphous polymers. The description is not completely satisfying because of improper limiting values at very short and very long times. Adequate corrections can be made to account for these differences at very short times [1]. Probing physical ageing by probing free volume hole sites by Positron Annihilation Lifetime Spectroscopy has revealed a small reduction of the average size of the holes as a function of ageing time and a strong dependence on the ortho‐Positronium intensity. It has been shown that the decrease of the intensity as a function of ageing time in several polymers is not a physical ageing effect, but a radiation effect of the positron source [2]. The stress relaxation and physical ageing behaviour of heterogeneous blends and crystalline polymers is, however, much more complicated than in homogeneous amorphous polymers. Both breakdown of the time temperature superposition as well as the time ageing time superposition has been observed [3]. There exists a remarkable correspondence between these thermorheologically complex polymer systems, allowing description and prediction of the relaxation long term behaviour after taking into account the structure of these systems.
Synthesis of new telechelic oligomers and macro‐monomers by “constructive degradation”
Authors: Ebdon John R.
Published: March 2011

Telechelic acrylic oligomers possessing terminal carboxylic acid, ketone, aldehyde or hydroxy groups can be synthesised in good yields by the ozonolysis of free radical copolymers of the appropriate acrylic monomer with a small amount of a 1,3‐diene, such as butadiene, 2,3‐dimethyl‐butadiene or 2,3‐diphenyl‐butadiene. The oligomers so‐prepared have high end‐functionalities (>98%), controllable average molecular weights, relatively narrow molecular weight distributions, and can be chain extended by a variety of means to give back high molecular weight polymers. Oligomers with perfect α‐phenyl ketone‐ω‐carboxylic acid functionality can be prepared by ozonolysing copolymers containing low concentrations of units derived from phenyl acetylene. Photolysis of copolymers of an alkyl vinyl ketone with monomers such as styrene yield, directly, oligomers with polymerisable unsaturated end‐groups, i.e. macromonomers.
Diacetylene‐containing polymers IV. Novel diacetylene‐containing polyamides and copolyamides
Authors: Fomin Sergei , Marin Margarita , Ogawa Takeshi
Published: March 2011

New monomers, bis(3‐ethynyl)dianilides, were synthesized from 3‐ethynylaniline and different diacid dichlorides and were polymerized by oxidative polycoupling to give soluble high molecular weight film forming diacetylene‐containing polyamides. UV‐induced and thermal cross‐linking of the polymer were studied. A correlation was found between the chain flexibility and the absoprtion peaks of visible spectra of cross‐linked polymer films. Third order nonlinear optical susceptibility (χ(3)) of the polymer films was in the range of 10−10‐10−9 esu.
Hydrogen bonding and the phase behavior of rod/coil mixtures
Authors: Tang Wei‐Long , Coleman Michael M. , Painter Paul C.
Published: March 2011

On the basis of a Flory lattice model it has been calculated that single phase rod/coil mixtures can be obtained and this is supported by some recent experimental results. However, in the absence of flexible side chains attached to the rigid rods, single phase mixtures are only obtained if the interactions between the rod and coil functional groups are very strong (e.g. phenol/pyridine) and the polymers are chemically similar (i.e. χ, describing non‐specific interactions, is small). If both flexible side chains and hydrogen bonding functional groups are attached to the rig rod, however, a much broader range of allowed χ values is obtained, so that with careful chemical design it should be possible to obtain a number of miscible rod/coil mixtures.
Liquid transport process in polymeric materials. Application with plasticized PVC with low matter transfer
Authors: Vergnaud J. M.
Published: March 2011

When a plasticized poly(vinyl chloride), (PVC), is in contact with a liquid, some matter transfer may take place, the liquid entering the polymer while the plasticizer leaves the polymer. These two mass transfers are controlled by transient diffusion and are connected with each other. No mathematical treatment can be made and numerical models taking all the facts into account are built and tested. New methods are studied, in order to prepare plasticized PVC with low matter transfer. The principle of the method consists of creating a steep profile of the plasticizer within the polymer with a low concentration on the surface. Other improvement is obtained by depositing on the polymer surface a thin layer of a liquid poorly soluble in the liquid stored in the PVC packaging.
The nature of the growing species in living cationic polymerization: Principles, stereochemistry, and in‐situ NMR analysis
Authors: Sawamoto Mitsuo
Published: March 2011

The objective of this paper is to discuss:

(i) the general approaches to living cationic polymerizations;

(ii) the nature of the growing species thus generated.

For the first, it is concluded that three general methods are currently available which involve the nucleophilic stabilization of the growing carbocations by (a) a suitable counteranion, (b) an added Lewis base, or (c) an added neutral salt. According to this view, a variety of initiating systems are classified. For the second, findings are presented for the recently developed living cationic polymerization of vinyl ethers by the HCl/SnCl4 initiating system in the presence of an added salt (nBu4N+Cl−). The nature of the growing species therein is discussed on the basis of the steric structure of the living polymers, relative to nonliving counterparts, and the in‐situ 13C NMR spectroscopic analysis of model reactions where the interaction of the growing end model [CH3CH(OR)Cl] with SnCl4 and the added salt is analyzed.
Some aspects of anionic butadiene copolymerization
Authors: Ying Shengkang
Published: March 2011

The relationship between ideal copolymerization behavior and the nature of reactive species in butyllithium (n‐BuLi) initiated anionic copolymerization of styrene (St)‐ butadiene (Bd) in nonpolar solvent has been discussed.

The monomer reactivity ratios (m.r.r.) for various reactive species were evaluated by kinetic study and statistical approach (using 13C NMR data) in St‐Bd anionic copolymerization system with THF as polar additive. The Markovian mechanisms for different propagating reactions in this complex copolymerizing system have been postulated.

Furthermore, “pseudo” zero order Markovian mechnism could be sophisticatedly established in the n‐BuLi/tertiary amyloxy potassium (t‐AmOK)/THF initiated St‐Bd copolymerization system, provided that the apparent rate constants of both monomers are equal. Thus, by adjusting the ratio of K/Li and THF/Li, copolymers with composition almost identical to the ratio of initial monomer feed composition at different stages of conversion could be obtained.
Anionic synthesis of in‐chain 3° amine‐functionalized polybutadienes
Authors: Quirk Roderic P. , Kuang Jianxin
Published: March 2011

Anionic copolymerizations of butadiene (M1) with excess 1‐(4‐dimethylaminophenyl)‐1‐phenylethylene (M2) were conducted in benzene at room temperature for 24–48h using sec‐butyllithium as initiator. Anisole, triethylamine and t‐butyl methyl ether were added in ratios of [B]/[RLi] = 60, 20, 30, respectively, to promote copolymerization. Narrow molecular weight distribution copolymers with M̄n = 14 × 103 to 32 × 103 g/mol (M̄w/M̄n =1.02–1.03) and 8,12 and 30 amine groups per chain for anisole, triethylamine and t‐butyl methyl ether, respectively, were obtained. The butadiene monomer reactivity ratios (r1) were 42, 33 and 14 for anisole, triethylamine and t‐butyl methyl ether, respectively.
Structure and reactivity of propagating centers in the anionic polymerization of 2‐vinylpyridine initiated by lithium derivative/triethylaluminium
Authors: Hubert Philippe , Soum Alain , Fontanille Michel , Hogen‐Esch Thieo E. , Dimov Dimo
Published: March 2011

The polymerization of 2‐vinylpyridine initiated by an organolithium derivative in the presence of Et3Al in toluene solution gives a polymer with enhanced syndiotactic content. This paper is devoted to the study of the structure and reactivity of this system. Model anions were studied by UV‐visible and 13C NMR spectroscopy. Propagation kinetics are followed by a calorimetric technique allowing the determination of the corresponding rate constants and thermodynamic parameters. These values are discussed in terms of the reaction mechanism of this polymerization.
Polymerization of dienes using organolithium compounds
Authors: Zgonnik Vladimir , Melenevskaja Elena
Published: March 2011

In this paper an interpretation is given of the polymerization mechanism of diene and styrene monomers with organolithium compounds (LOC).An attempt will be made to correlate the nature of living chains to the structure of the polymer formed.
NMR Studies of polymeric materials ‐ an overview
Authors: Cheng H. N. , Early Thomas A.
Published: March 2011

NMR has been used extensively in studies of synthetic polymers. The approaches employed may require solution NMR, solid state NMR, or NMR imaging. In each case, different techniques and analytical methodologies have been devised to facilitate experimentation or to maximize information output. These techniques are not mutually exclusive and often provide complementary information. A selective review is made herewith of polymer/NMR studies, with emphasis on the contributions made at NMR symposia held in Detroit in October, 1993 as part of the 20th FACSS meeting.
Applications of triple resonance NMR techniques to the study of polymer structure and reactivity
Authors: Rinaldi Peter L. , Li Lan , Hensley Darlene R. , Ray Dale G. , Harwood H. James
Published: March 2011

The utility of isotopic labeling combined with triple resonance nuclear magnetic resonance (NMR) techniques for polymer structure and reactivity investigations will be demonstrated. One dimensional (1D) and two dimensional (2D) 1H/19F/13C triple resonance NMR experiments have been used to study the structure of fluoropolymers; and 1H/2H/13C triple resonance techniques have been used to study the reactivity of poly[(styrene‐alt‐(methyl methacrylate)] and the structure of deuterated polybutadiene. These methods provide a unique ability to selectively detect resonances of structural features that are present in minute amounts in polymers, without interference from the much larger signals of the rest of the polymer.
Sequential identification of polymer microstructures by heteronuclear NMR correlations
Authors: Beshah Kebede
Published: March 2011

A description of a systematic NMR methodology for the characterization of polymers in solution is presented. The method utilizes a set of two dimensional (2D) heteronuclear NMR correlation experiments. It is especially optimized for polymers that have characteristic short spin‐spin relaxation times. Microstructures of homopolymers and copolymers are determined objectively since the analysis is based only on near neighbor correlations of all carbon and hydrogen atoms. Applications to poly(acrylic acid) and ethylene/vinyl acetate copolymer are presented.
The analysis of heterogenous polymer systems using solid‐state NMR techniques
Authors: Sullivan Mark J.
Published: March 2011

Two different types of high resolution solid‐state 13C‐1H cross depolarization experiments were applied to a rubber toughened thermoset polymer. A polypropylene blend was examined using a solid‐echo 1H wide line pulse sequence over the temperature range from 27 to 197°C. The frequency domain spectra were curve fitted to obtain the relative abundances of the three distinct 1H T2 components as a function of temperature.
Dynamics of the interface in a model composite system
Authors: Blum Frank D.
Published: March 2011

A review of recent experiments from the authors laboratory on the dynamics of aminofunctional silane coupling agents is given. Of special emphasis are two coupling agents, aminopropylsilane (APS) and aminobutylsilane (ABS) which were deuterated in the γ‐position. These two coupling agents have similar chemical behavior, but different dynamics. Deuterium NMR studies reveal that the APS moves slower on the silica surface than ABS. The mobility of the interfacial ABS was also found to be significantly slowed when it was overcoated with a polymerized layer of bismaleimide to form a composite. When the composite was treated with water, the interfacial mobility of the ABS increased. The flexural strength of the APS treated composite was the highest compared to ABS‐treated and bulk glass in an epoxy‐glass composite.
NMR measurement of the surface dynamics of poly(dimethylsiloxane) adsorbed on silica gel
Authors: Rethwisch David G. , van Alsten John , Dybowski Cecil R.
Published: March 2011

CPMAS‐DD 13C NMR spectroscopy was used to examine the mobility of poly(dimethylsiloxane) adsorbed on silica gel (PDMS/SiO2) at submonolayer coverages. The spin‐lattice relaxation time in the rotating frame (T1ρH) decreased linearly with increasing loading. This is consistent with a decrease in the mobility of the polymer segments as the loading is increased. The decrease in mobility results from interpolymer interference. We propose a model that explains these results in terms of a surface intrinsic viscosity that incorporates the polymer‐polymer interactions on the surface.
Intermolecular interactions in polymer blends: 1D and 2D NMR studies
Authors: Mirau Peter A. , White Jeffery L. , Heffner Sharon A.
Published: March 2011

Most mixtures of high molecular weight polymers are not miscible in the absence of specific intermolecular interactions. We have used two dimensional NMR in solutions and in the solid state to probe these interactions and to gain a molecular level understanding of the forces that control polymer blend formation. The results show that weak, but specific intermolecular interactions often control the phase structure of polymer blends.
NMR imaging as a new tool for rheology
Authors: Sinton Steve W. , Chow Andrea W. , Iwamiya Joseph H.
Published: March 2011

Examples of NMR imaging used to study the evolution of microstructure and flow velocities in sheared, highly filled suspensions are described. Fast NMR imaging methods were used to freeze the motion in a falling‐ball experiment, allowing us to monitor the local concentrations of suspended particles and ball position during the course of the experiment The migration of particles induced by shear and concentration gradients was followed in a Couette cell. Flow imaging methods were developed and applied to a Newtonian fluid and a non‐Newtonian suspension flowing in an axisymmetric pipe contraction.
Structure‐property relationships in thermochromic polythiophene derivatives
Authors: Roux Claudine , Leclerc Mario
Published: March 2011

Two categories of thermochromic polythiophene derivatives have been identified, which are dependent upon the nature and the position of the substituents. A molecular mechanism is proposed that can explain the thermally induced optical transitions observed in these materials.
Some unusual features of the configuration of polymer loops in a melt
Authors: Brereton Michael , Vilgis Thomas A.
Published: March 2011

A diversity of structural features can be imposed on a melt of polymer loops by controlling the linking number between each pair of loops. For the simple case of unlinked loops, considered in this paper, new statistical weighting factors have been found which depend on the global configurational properties of writhe and self inductance. The separate effect of these terms is extreme: the writhe term favours rod‐like statistics, whereas the inductance favours globular configurations. Together the two terms tend to cancel each other in a way which is reminiscent of the screened potential in polymer chain melts. The result is that the exponent which describes the size of an unlinked loop in a melt of unlinked loops is perturbed from the gaussian result of 0.5 to 0.45.
Forty years of industrial developments in the field of isotactic polyolefins
Authors: Galli P.
Published: March 2011

The interest for the stereospecific polymerization of olefins discovered by prof. Natta in 1954 was so high that only a few years elapsed between the discovery and the commercialization of polypropylene. The polypropylene discovery generated a tremendous scientific and technological effort for the development of the catalyst, the process, the products. The fundamental achievements in the polypropylene technology had a significant impact over the polyolefin technology in general. Thanks to it, polyolefinic polymers, copolymers and rubbers, polyefinic based materials and alloys via heterogeneous Ziegler‐Natta catalyst polymerization are today largerly the most important family of plastic materials.

The ability to vary melt flow and the broad properties range of these materials, the excellent thermal and physical‐mechanical properties of isotactic polyolefins together with the favorable economics and their full and easy recyclability widen the concept of monomaterial application fuelling their dynamic expansion since the early sixties.