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Modern State of Models for Fundamental Adhesion - A Review Extended Abstract
Possart, Wulff The Society of Adhesion and Interface 2002 접착 및 계면 Vol.3 No.1
Advanced adhesive technologies and demanding applications of adhesive joints can no longer be developed successfully by the traditional "trial and error" approach. Appropriate technical solutions require reference to a reliable basis of well-established scientific knowledge about the elementary mechanisms of adhesion (i.e. the 'fundamental adhesion') as they are responsible for the capability of the compound w transmit mechanical force between the adhesive and the substrate surface (i.e. the 'practical adhesion'). Adhesion mechanisms also influence the formation of polymer structure in the adhesive and the resulting macromolecular dynamics in the interphase that is formed in the adhesive near to the substrate. These manifold molecular factors rule the macroscopic behaviour of an adhesive bond line in terms of mechanical and other physical properties as well as in terms of durability. This paper reviews the level of refinement that understanding of fundamental adhesion has achieved up to now.
Brazing in SiH4-doped inert gases: A new approach to an environment friendly production process
Ulrich Holländer,Daniel Wulff,André Langohr,Kai Möhwald,Hans Jürgen Maier 한국정밀공학회 2020 International Journal of Precision Engineering and Vol.7 No.6
Engineering under protective atmospheres or in vacuum allows the production of materials and components, where the absence of oxygen is an essential requirement for a successful processing. Ideally, joining or coating of (and with) metallic materials needs oxide free material surfaces, in order to achieve durable joints or coatings. Using the established technology of brazing in controlled atmosphere, fundamental physical mechanisms for deoxidation of metal surfaces are presented and the role of oxygen and water residue in the process atmosphere is analyzed. Furthermore, the doping of gases with monosilane for generating virtually oxygen-free process atmospheres is introduced and its advantages for an oxygen-free production are discussed.
Filming the Birth of Molecules and Accompanying Solvent Rearrangement
Lee, Jae Hyuk,Wulff, Michael,Bratos, Savo,Petersen, Jakob,Guerin, Laurent,Leicknam, Jean-Claude,Cammarata, Marco,Kong, Qingyu,Kim, Jeongho,Møller, Klaus B.,Ihee, Hyotcherl American Chemical Society 2013 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.135 No.8
<P>Molecules are often born with high energy and large-amplitude vibrations. In solution, a newly formed molecule cools down by transferring energy to the surrounding solvent molecules. The progression of the molecular and solute–solvent cage structure during this fundamental process has been elusive, and spectroscopic data generally do not provide such structural information. Here, we use picosecond X-ray liquidography (solution scattering) to visualize time-dependent structural changes associated with the vibrational relaxation of I<SUB>2</SUB> molecules in two different solvents, CCl<SUB>4</SUB> and cyclohexane. The birth and vibrational relaxation of I<SUB>2</SUB> molecules and the associated rearrangement of solvent molecules are mapped out in the form of a temporally varying interatomic distance distribution. The I–I distance increases up to ∼4 Å and returns to the equilibrium distance (2.67 Å) in the ground state, and the first solvation cage expands by ∼1.5 Å along the I–I axis and then shrinks back accompanying the structural change of the I<SUB>2</SUB> molecule.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jacsat/2013/jacsat.2013.135.issue-8/ja312513w/production/images/medium/ja-2012-12513w_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja312513w'>ACS Electronic Supporting Info</A></P>
Kim, Tae Kyu,Lee, Jae Hyuk,Wulff, Michael,Kong, Qingyu,Ihee, Hyotcherl WILEY-VCH Verlag 2009 CHEMPHYSCHEM -WEINHEIM- Vol.10 No.12
<P>Information about temporally varying molecular structure during chemical processes is crucial for understanding the mechanism and function of a chemical reaction. Using ultrashort optical pulses to trigger a reaction in solution and using time-resolved X-ray diffraction (scattering) to interrogate the structural changes in the molecules, time-resolved X-ray liquidography (TRXL) is a direct tool for probing structural dynamics for chemical reactions in solution. TRXL can provide direct structural information that is difficult to extract from ultrafast optical spectroscopy, such as the time dependence of bond lengths and angles of all molecular species including short-lived intermediates over a wide range of times, from picoseconds to milliseconds. TRXL elegantly complements ultrafast optical spectroscopy because the diffraction signals are sensitive to all chemical species simultaneously and the diffraction signal from each chemical species can be quantitatively calculated from its three-dimensional atomic coordinates and compared with experimental TRXL data. Since X-rays scatter from all the atoms in the solution sample, solutes as well as the solvent, the analysis of TRXL data can provide the temporal behavior of the solvent as well as the structural progression of all the solute molecules in all the reaction pathways, thus providing a global picture of the reactions and accurate branching ratios between multiple reaction pathways. The arrangement of the solvent around the solute molecule can also be extracted. This review summarizes recent developments in TRXL, including technical innovations in synchrotron beamlines and theoretical analysis of TRXL data, as well as several examples from simple molecules to an organometallic complex, nanoparticles, and proteins in solution. Future potential applications of TRXL in femtosecond studies and biologically relevant molecules are also briefly mentioned.</P> <B>Graphic Abstract</B> <P>Time and motion: Time-resolved X-ray liquidography (see picture) can directly probe the structural dynamics and spatiotemporal kinetics of the liquid phase with unprecedented spatial and temporal resolution. Recent developments in this method, including technical innovations, theoretical analysis, and several examples ranging from simple molecules to protein solutions, are reviewed. <img src='wiley_img/14394235-2009-10-12-CPHC200900154-content.gif' alt='wiley_img/14394235-2009-10-12-CPHC200900154-content'> </P>
Kong, Qingyu,Lee, Jae Hyuk,Kim, Kyung Hwan,Kim, Joonghan,Wulff, Michael,Ihee, Hyotcherl,Koch, Michel H. J. American Chemical Society 2010 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.132 No.8
<P>Ultrafast (ps) time-resolved X-ray scattering was used to study the structural dynamics of Ru<SUB>3</SUB>(CO)<SUB>12</SUB> in cyclohexane after photolysis at 260 nm. Two intermediates form after 100 ps at the onset of the reaction: Ru<SUB>3</SUB>(CO)<SUB>10</SUB> for the CO loss channel and Ru<SUB>3</SUB>(CO)<SUB>11</SUB>(μ-CO) for the metal−metal cleavage channel. In our previous study at 390 nm, by contrast, three intermediates were observed simultaneously at the onset of the reaction that all relax back to Ru<SUB>3</SUB>(CO)<SUB>12</SUB> with different lifetimes. The major difference between photolysis at 260 and 390 nm is that in the first case Ru<SUB>3</SUB>(CO)<SUB>10</SUB>(μ-CO) is formed by bimolecular recombination of Ru<SUB>3</SUB>(CO)<SUB>10</SUB> with a free CO in 50 ns, whereas in the second case it forms directly from Ru<SUB>3</SUB>(CO)<SUB>12</SUB> at the onset of the reaction. The differences between the photofragmentation pathways are related to the absorption bands available at the two wavelengths. The extrema in the difference radial distribution functions (RDFs) are unambiguously assigned by decomposing the total signal into contributions from the solutes, the solvent and the solute−solvent cross-terms, and also contributions from each candidate species. The difference RDFs reveal the depletion of Ru−Ru bonds (2.88 Å) in the initial Ru<SUB>3</SUB>(CO)<SUB>12</SUB> molecule and formation of Ru<SUB>3</SUB>(CO)<SUB>10</SUB> as the major photoproduct. The high-resolution X-ray (88 keV) scattering pattern of pure liquid C<SUB>6</SUB>H<SUB>12</SUB> indicates that the solvent dynamics at early time delays is due to broadening of the intermolecular interatomic correlations at constant volume, whereas during thermal expansion at longer time delays, it results from shifts in these correlations.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jacsat/2010/jacsat.2010.132.issue-8/ja9097548/production/images/medium/ja-2009-097548_0010.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja9097548'>ACS Electronic Supporting Info</A></P>
Polymer Catalysts by Molecular Imprinting: A Labile Covalent Bonding Approach
Kim, Jong Man,An, Gwang Deok,Alexander G. Strikovsky,Guenter Wulff Korean Chemical Society 2001 Bulletin of the Korean Chemical Society Vol.22 No.7
An imprinting technique with labile covalent interactions has been developed in the design of new polymer catalysts. The template monomer 2 was prepared and copolymerized with DVB or EDMA to provide the polymer with a cavity having the shape of th e transition state of the reaction as well as binding sites for the substrate and catalytic functionalities. The rate of hydrolysis of diphenyl carbonate (1) in the presence of the imprinted polymer IP-DVB-THF was found to be 120 times faster than the background uncatalyzed reaction. A Km of 32 mM and a kcat of 1.8 ${\times}$ 10-3min-1 were observed from Michaelis-Menten kinetics with the imprinted polymer IP-DVB-THF.