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101.
Novel responsive solids were prepared by randomly cross-linking the polyisoprene chains of a disordered polystyrene-polyisoprene block copolymer. Our experiments show that block copolymer chains, composed of hundreds of repeat units, can undergo reversible order-disorder transitions despite the quenched randomness that arises due to the attachment of one of the blocks to a cross-linked network. The structure, properties, and phase behavior of these materials are determined by a delicate interplay between the density of cross-links and the nature of the ordered state. 相似文献
102.
Schmidt WG Hahn PH Bechstedt F Esser N Vogt P Wange A Richter W 《Physical review letters》2003,90(12):126101
The InP(001)(2 x 1) surface has been reported to consist of a semiconducting monolayer of buckled phosphorus dimers. This apparent violation of the electron counting principle was explained by effects of strong electron correlation. Combining first-principles calculations with reflectance anisotropy spectroscopy and LEED experiments, we find that the (2 x 1) reconstruction is not at all a clean surface: it is induced by hydrogen adsorbed in an alternating sequence on the buckled P dimers. Thus, the microscopic structure of the InP growth plane relevant to standard gas phase epitaxy conditions is resolved and shown to obey the electron counting rule. 相似文献
103.
Hervé G Hahn DU Hervé AC Goodworth KJ Hill AM Hailes HC 《Organic & biomolecular chemistry》2003,1(2):427-435
Methodologies to access water soluble large ringed calixarenes in good yield using efficient synthetic procedures have been investigated. Symmetrical partial functionalisations at the lower rim are described using activated [n]ethylene glycol chains and the addition behaviour contrasted with that of bromoalkanenitriles which proceeds with no observed regioselectivity. Full functionalisations of the calixarenes bearing hydrophilic groups are then investigated and a two-step procedure established which appears to be generally applicable for the addition of different [n]ethylene glycol chains. Furthermore, difunctionalisation under different reaction conditions are described. Throughout, strategies for the characterisation of these high mass compounds are outlined. 相似文献
104.
The isothermal gas adsorption of two hexane isomers (n-hexane and cyclohexane) in the mesopores of MCM-41 silica have been investigated by small angle neutron scattering (SANS). This has been achieved by performing SANS measurements under contrast matching conditions for the silica matrix and condensed hydrocarbon confined in the mesopores. Insight into the kinetics of adsorption have been derived from changes in the intensity of the (100) diffraction peak associated with the ordered hexagonal mesoporous structure of the MCM-41 silica. 相似文献
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108.
Christian Grabner Heiko Hahn Ulrike Leopold-Wildburger Stefan Pickl 《European Journal of Operational Research》2009
For the analysis presented in this paper we use experiments to study human behavior in a simulation environment based on a simple Lotka–Volterra predator–prey ecology. The aim is to study the influence of different harvesting strategies and of certain personality traits derived from the Hamburg Personality Inventory (HPI) [Andresen, B., 2002. HPI – Hamburger Persönlichkeitsinventar. Hogrefe, Göttingen] on the outcome in terms of sustainability and economic performance. 相似文献
109.
Houxiang Sean Tang Theresa J. Hermel‐Davidock Stephen F. Hahn Dan J. Murray Robert C. Cieslinski Nikhil E. Verghese Ha Q. Pham 《Journal of Polymer Science.Polymer Physics》2009,47(4):393-406
Microdeformation behavior in nanostructured block copolymer‐toughened epoxy resins, or templated epoxy thermosets, was studied using an in situ tensile deformation technique performed directly in a transmission electron microscope. The observed microdeformation modes were found to correlate well with the macroscopic mechanical properties of the materials. In the order of decreasing macroscopic fracture toughness, the microdeformation modes were observed to change from large uniform plastic deformation over an extensive area, to localized plastic deformation bands, to little plastic deformation observed in the most brittle material. A similar trend was also observed when samples of the same material were tested at different temperatures, reflecting changes in the deformation mechanism as a function of temperature. Structural defects were observed in nanotoughening phases when plastic deformation was observed. The implication of the observed microdeformation modes to the macroscopic toughening mechanisms is discussed in the context of the micromorphology of the nanometer sized toughening phases and parameters of the epoxy matrix chemistry such as bromination, molecular weight, and interfacial miscibility. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 393–406, 2009 相似文献
110.
Brad M. Rosen Gerard Lligadas Christian Hahn Virgil Percec 《Journal of polymer science. Part A, Polymer chemistry》2009,47(15):3940-3948
The development of a novel nucleophilic thio‐bromo “Click” reaction, specifically base‐mediated thioetherification of thioglycerol with α‐bromoesters was reported in an earlier article. The combination of this thio‐bromo click reaction with subsequent acylation with 2‐bromopropionyl bromide provides an iterative two‐step divergent growth approach to the synthesis of a new class of poly(thioglycerol‐2‐ propionate) (PTP) dendrimers. In this article, the addition of a third step, the single‐electron transfer living radical polymerization (SET‐LRP) of methyl acrylate (MA), was shown to provides access to a three‐step “branch” and “grow” divergent approach to dendritic macromolecules wherein poly(methyl acrylate) (PMA) connects the branching subunits. This facile methodology can provide a diversity of dendritic macromolecular topologies and will ultimately provide the means to the development of self‐organizable dendritic macromolecules. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3940–3948, 2009 相似文献