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991.
Mireia Morell Albena Lederer Xavier Ramis Brigitte Voit Angels Serra 《Journal of polymer science. Part A, Polymer chemistry》2011,49(11):2395-2406
Well‐defined multiarm star copolymers, hyperbranched poly(glycidol)‐b‐poly(ε‐caprolactone), with an average of 100–110 arms per molecule and a molecular weight of arms of 3000 g/mol (PGOH‐b‐PCL30) and 1000 g/mol (PGOH‐b‐PCL10) were synthesized by cationic ring‐opening polymerization of ε‐caprolactone from a poly(glycidol) core and used to modify diglycidylether of bisphenol A formulations. The curing process, studied by dynamic scanning calorimetry, was only slightly retarded when PGOH‐b‐PCLx were added to the formulation. By rheometry, the effect of this new topology and the arm length on the complex viscosity (η*) and gelation of the reactive mixture was analyzed in detail. The addition of these new reactive modifiers decreases the global shrinkage and increases the conversion at gelation. In addition, the modified thermosets have an improved reworkability. The homogeneity of pure DGEBA and modified thermosets was proved by dynamic thermomechanical analysis and electronic microscopy (FESEM). Addition of star‐like structures led to a more toughened fracture of the thermoset in comparison to pure DGEBA. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 相似文献
992.
Dr. Rasmus Linser Muralidhar Dasari Dr. Matthias Hiller Dr. Victoria Higman Uwe Fink Dr. Juan‐Miguel Lopez del Amo Stefan Markovic Liselotte Handel Brigitte Kessler Dr. Peter Schmieder Prof. Dr. Dieter Oesterhelt Prof. Dr. Hartmut Oschkinat Prof. Dr. Bernd Reif 《Angewandte Chemie (International ed. in English)》2011,50(19):4237-4237
993.
An agent, consisting of an unmanned aerial vehicle (UAV) carrying strapped-down sensors, is to examine a number of unidentified objects within a given search area, collect information, and utilize that information to classify the objects. The problem is challenging because the mission time is often limited, the agent is only provided with partial a priori information, and the amount of information that the sensor can measure is dependent on the relative position of the agent with respect to the object. Our technical approach is three-fold. First, we model the motion of the agent using a kinematic model with constant altitude. Second, we use a performance prediction model that gives the probability of target discrimination as a function of the range from the sensor to the object. Third, a linear classifier that utilizes Bayes?? theorem diagnoses the status of the objects of interest while an information-theoretic measure is used to quantify the uncertainty in classification. We pose an optimal control problem that minimizes the classification uncertainty while taking differential constraints and the time history of the agent??s steering decisions as the control input. We investigate whether maximizing information by choosing informative paths always minimizes the classification uncertainty. 相似文献
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Udo Engelhardt Thomas Bünger Heinz Viertel Brigitte Stromburg Konrad Giersdorf 《Phosphorus, sulfur, and silicon and the related elements》2013,188(3-4)
Abstract Reported are synthetic routes to inorganic heterocycles of different ring size, containing phosphorus, hydrazine, silicon and other elements as ring components. Steric effects that cause saturated sixmembered rings to adopt an unusual twist conformation are discussed (temperature dependent NMR-spectra, X-ray structures). 相似文献
998.
Bernd E. Diebl Yang Li Mirza Cokoja Fritz E. Kühn Narayanan Radhakrishnan Stefan Zschoche Hartmut Komber Hui Yee Yeong Brigitte Voit Oskar Nuyken Phillip Hanefeld Hans‐Michael Walter 《Journal of polymer science. Part A, Polymer chemistry》2010,48(17):3775-3786
Acetonitrile ligated molybdenum (III) complexes of the structure [MoCl(NCCH3)5]2+ bearing different weakly coordinating anions [B(C6F5)4]? (WCA a), [B{C6H3(m‐CF3)2}4]? (WCA b) and [(C6F5)3B‐C3H3N2‐B(C6F5)3]? (WCA c) were applied as homogeneous catalysts of the polymerization of isobutylene. High monomer conversions were obtained in short reaction times (<30 min). The molecular weight of the resulting polyisobutylene is nearly independent of parameters such as temperature, solvent, monomer concentration, but is strongly influenced by the type of WCA and by chain transfer reactions which were observed in these systems. Highly reactive low molecular weight polyisobutylenes (Mn < 2000 g/mol) were obtained with a high content of exo double bond end groups as shown by 1H NMR analysis. Furthermore, experiments were performed to reduce the isomerization of these exo end groups into other internal double bonds by varying the polymerization parameters. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3775–3786, 2010 相似文献
999.
Niranjan Karak Buddhadeb Roy Brigitte Voit 《Journal of polymer science. Part A, Polymer chemistry》2010,48(18):3994-4004
A series of s‐triazine‐based hyperbranched polyethers (HBPE) have been synthesized to obtain thermostability but flexible polymers by an interfacial polycondensation of different diols as A2 and cyanuric chloride as B3 monomers using A2 + B3 approach in the presence of a phase transfer catalyst. The polymerization reaction parameters are optimized, and the results indicate that the optimum conditions for the interfacial polycondensation are a 2:3 mole ratio of cyanuric chloride to diol using butanediol, benzyldimethylhexadecyl ammonium chloride as the catalyst, dichloromethane as the organic solvent, and a three‐step procedure with keeping the reaction mixture at different low temperatures for 2h/2h/5h. Other techniques such as high‐temperature solution, one‐step polycondensation, and transesterification were also carried out to synthesize the HBPE but proved to be not suitable due to large number of side reactions. The synthesized polymers were characterized by FTIR, 1H NMR, and 13C NMR spectroscopy, hydroxyl number determination, solution viscosity measurements, and GPC analysis. The thermal behavior of the hyperbranched polymer was investigated by thermogravimetric analysis and differential scanning calorimetry. All the results were compared with those from an analogous linear polyether, obtained from 2‐methoxy‐4,6‐dichloro‐s‐triazine and butanediol by using the same polymerization technique. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3994–4004, 2010 相似文献
1000.
Mireia Morell David Foix Albena Lederer Xavier Ramis Brigitte Voit Àngels Serra 《Journal of polymer science. Part A, Polymer chemistry》2011,49(21):4639-4649
A well‐defined multiarm star copolymer poly(styrene)‐b‐poly(ε‐caprolactone) (PSOH‐b‐PCL) with an average number of PCL arms per molecule of 60 has been prepared. 4‐Chloromethyl styrene (4‐CMS) was polymerized by means of atom transfer radical polymerization (ATRP) to obtain a hyperbranched poly(styrene) with chlorines as terminal groups. Subsequently, chlorines were substituted by reaction with diisopropanolamine (DIPA) to give the hydroxyl‐ended derivative. Finally, the hydroxyl‐ended hyperbranched poly(styrene) has been used as a macroinitiator core to polymerize ε‐caprolactone by means of cationic ring‐opening polymerization so as to obtain the star copolymer. In a second step, PSOH‐b‐PCL was used as reactive modifier of diglycidylether of bisphenol A formulations cured by 1‐methyl imidazole (1‐MI) obtaining nanostructured thermosets. The curing process was studied by dynamic scanning calorimetry and Fourier transform infrared spectroscopy (FTIR). By rheometry, the effect of this new polymer topology on the complex viscosity (η*) of the reactive mixture and on the gelation process was also analyzed. The thermomechanical characteristics of the modified materials were determined. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 相似文献