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101.
102.
Balz M Barriau E Istratov V Frey H Tremel W 《Langmuir : the ACS journal of surfaces and colloids》2005,21(9):3987-3991
The formation of biominerals by living organisms is governed by the cooperation of soluble and insoluble macromolecules with peculiar interfacial properties. To date, most of the studies on mineralization processes involve model systems that only account for the existence of one organic matrix and thus disregard the interaction between the soluble and insoluble organic components that is crucial for a better understanding of the processes taking place at the inorganic-organic interface. We have set up a model system composed of a matrix surface, namely, a self-assembled monolayer (SAM), and a soluble component, hyperbranched polyglycerol. The model mineral calcium carbonate displays diverse polymorphism. It could be demonstrated that the phase selection of calcium carbonate is controlled by the cooperative interaction of the SAM and hyperbranched polyglycerol of different molecular weights (M(n) = 500-6000 g/mol) adsorbed to the SAM. Our studies showed that hyperbranched polyglycerol is adsorbed to polar as well as to nonpolar SAMs. This effect can be related to its highly flexible structure and its amphiphilic character. The adsorption of hyperbranched polyglycerol to the SAMs with different surface polarities resulted in the formation of aragonite for alkyl-terminated SAMs and no phase selection for carboxylate-terminated SAMs. 相似文献
103.
Saxena A Castán T Planes A Porta M Kishi Y Lograsso TA Viehland D Wuttig M De Graef M 《Physical review letters》2004,92(19):197203
Based on experimental observations of modulated magnetic patterns in a Co0.5Ni0.205Ga0.295 alloy, we propose a model to describe a (purely) magnetic tweed and a magnetoelastic tweed. The former arises above the Curie (or Néel) temperature due to magnetic disorder. The latter results from compositional fluctuations coupling to strain and then to magnetism through the magnetoelastic interaction above the structural transition temperature. We discuss the origin of purely magnetic and magnetoelastic precursor modulations and their experimental thermodynamic signatures. 相似文献
104.
Bourles E Alves de Sousa R Galardon E Giorgi M Artaud I 《Angewandte Chemie (International ed. in English)》2005,44(38):6162-6165
105.
We study the driving-rate and temperature dependence of the power-law exponents that characterize the avalanche distribution in first-order phase transitions. Measurements of acoustic emission in structural transitions in Cu-Zn-Al and Cu-Al-Ni are presented. We show how the observed behavior emerges within a general framework of competing time scales of avalanche relaxation, driving rate, and thermal fluctuations. We confirm our findings by numerical simulations of a prototype model. 相似文献
106.
Emilie Barriau Alejandra García Marcos Holger Kautz Holger Frey 《Macromolecular rapid communications》2005,26(11):862-867
Summary: A convenient three‐step strategy has been developed for the preparation of well‐defined amphiphilic, linear‐hyperbranched block copolymers by hypergrafting. The synthetic procedure is based on a combination of carbanionic polymerization with the alkoxide‐based, controlled ring‐opening multibranching polymerization of glycidol. A linear AB diblock copolymer polystyrene‐block‐polybutadiene (PS‐b‐PB) with narrow polydispersity was obtained by anionic copolymerization. Subsequent hydroxylation by hydroboration led to PS508‐b‐(PB‐OH)56, used as macroinitiator for the polymerization of glycidol under slow monomer addition conditions.
107.
Coraline Sester Fabrice Ofridam Noureddine Lebaz Emilie Gagnire Denis Mangin Abdelhamid Elaissari 《先进技术聚合物》2020,31(3):440-450
Poly (methyl methacrylate) derivatives such as Eudragit are largely used for drug encapsulation and in controlled oral drug delivery. With special focusing on those applications, solubilization and precipitation conditions of two pH‐sensitive Eudragit polymers, namely, L100 and E100, were investigated via systematic studies. Effects of various physicochemical parameters such as pH, polymer concentration, salinity, buffer concentration, and incubation time on the solubilization and precipitation of these polymers were investigated. In addition, pH titration of both polymers was reported. Considering both macroscopic and quantitative aspects such as the final mean particle size, size distribution, morphology, and the zeta potential, it was established that the different precited parameters could not be dissociated and exert a synergic action on the solubilization and precipitation of both polymers. Titration curves revealed two equivalences that helped estimating carboxylic content of Eudragit L100 (6 mmol/g) and ammonium content of Eudragit E100 (4 mmol/g). In this study, the solubilization and the precipitation domains were for the first time clearly established by considering the above‐mentioned parameters. Moreover, it was found that Eudragit L100 and E100 cannot be considered as classic polyelectrolytes; in fact, solubilization and precipitation domains were not affected by ionic strength. 相似文献
108.
Thermal Behavior of d‐Ribose Adsorbed on Silica: Effect of Inorganic Salt Coadsorption and Significance for Prebiotic Chemistry 下载免费PDF全文
Mariame Akouche Maguy Jaber Emilie‐Laure Zins Marie‐Christine Maurel Jean‐Francois Lambert Thomas Georgelin 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(44):15834-15846
Understanding ribose reactivity is a crucial step in the “RNA world” scenario because this molecule is a component of all extant nucleotides that make up RNA. In solution, ribose is unstable and susceptible to thermal destruction. We examined how ribose behaves upon thermal activation when adsorbed on silica, either alone or with the coadsorption of inorganic salts (MgCl2, CaCl2, SrCl2, CuCl2, FeCl2, FeCl3, ZnCl2). A combination of 13C NMR, in situ IR, and TGA analyses revealed a variety of phenomena. When adsorbed alone, ribose remains stable up to 150 °C, at which point ring opening is observed, together with minor oxidation to a lactone. All the metal salts studied showed specific interactions with ribose after dehydration, resulting in the formation of polydentate metal ion complexes. Anomeric equilibria were affected, generally favoring ribofuranoses. Zn2+ stabilized ribose up to higher temperatures than bare silica (180 to 200 °C). Most other cations had an adverse effect on ribose stability, with ring opening already upon drying at 70 °C. In addition, alkaline earth cations catalyzed the dehydration of ribose to furfural and, to variable degrees, its further decarbonylation to furan. Transition‐metal ions with open d‐shells took part in redox reactions with ribose, either as reagents or as catalysts. These results allow the likelihood of prebiotic chemistry scenarios to be evaluated, and may also be of interest for the valorization of biomass‐derived carbohydrates by heterogeneous catalysis. 相似文献
109.
110.
Estelle Gérard Emilie Bessy Gregory Hénard Laurent Ducoroy Thierry Verpoort Jacqueline Marchand‐Brynaert 《Journal of polymer science. Part A, Polymer chemistry》2011,49(23):5087-5099
The surface of meltblown poly(butylene terephthalate) (PBT) nonwoven was modified by photochemistry using the photolinker O‐succinimidyl 4‐azido‐2,3,5,6‐tetrafluorobenzoate for the introduction of activated ester functions and then coupling of molecular probes or biomolecules. Approximately 4000 pmol of (L )‐4,5‐[3H]‐lysine was fixed per PBT sample (1.13 cm2) and measured by liquid scintillation counting. The method consisted in a two‐step process: (a) coating of the clip (0.05 mg/sample) on the fibrous surface of the PBT followed by UV irradiation (30 min, 254 nm) and (b) coupling of amine‐terminated molecules (10?3 M in phosphate buffer–CH3CN [1/1, v/v], 20 h). Moreover, about 2000 pmol of 3H‐lysine can be immobilized on the PBT surface after UV irradiation (without clip) by aminolysis reactions with the created oxygenated functions. The derivatizations (via the clip and UV irradiation only) were stable after long‐term heating at 100 °C in water or under steam‐sterilization conditions. They induce neither modifications of the nonwoven morphology nor cytotoxicity. This method was applied for the grafting of peptides Gly‐Arg‐Gly‐Asp‐Ser and Gly‐Gly‐Gly‐Gly‐Gly to perform blood filtration experiments and to retain the leukocytes. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 相似文献