DOCSLIB.ORG

A Curious Antipathy for Water Hydrophobicity but Few Agree on the Details

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
A Curious Antipathy for Water Hydrophobicity but Few Agree on the Details PERSPECTIVES apparent change in angular direction to a dis- numbers of objects, a critical precondition for matic advances are anticipated, with the com- tant object as Earth orbits the Sun during a year accurate mass and orbit determinations. bination of the LHC and Gaia. as a fundamental distance scale (9). Gaia pre- Dark matter is the dominant gravitating cision is an improvement on the best astrome- mass in the Universe. It is perhaps a mix of References and Notes try currently available by some 3 orders of several ingredients, with different contribu- 1. V. Springel, C. S. Frenck, S. D. M. White, Nature 440, 1137 (2006). magnitude, while its sensitivity provides an tions dominant on different scales, from the 2. V. Belokurov et al., Astrophys. J. 654, 897 (2007). improvement of 4 orders of magnitude. One of extremely small scale of weakly interacting 3. G. Gilmore et al., Astrophys. J. 663, 948 (2007). Gaia’s prime subjects will be galaxy evolution, massive particles to the very long scales of 4. M. Walker et al., Astrophys. J. 667, L53 (2007). 5. G. Gilmore, R. F. G. Wyse, K. Kuijken, Annu. Rev. Astron. including measuring the distribution of dark massive neutrinos. Disentangling this mix Astrophys. 27, 555 (1989). matter on whatever scales it is found. The tech- requires quantitative determination of the 6. S. Majewski, Annu. Rev. Astron. Astrophys. 31, 575 nically most difficult aspect of dark matter three-dimensional distribution of mass in dark (1993). 7. K. Freeman, J. Bland-Hawthorn, Annu. Rev. Astron. studies in astrophysics is precision mass mea- matter–dominated systems on astrophysical Astrophys. 40, 487 (2002). surement. Usually having access only to line- scales to complement direct detection and cre- 8. European Space Agency, Research and Scientific Support of-sight velocity data and knowing little of ation experiments on Earth. As galaxies have Department, www.rssd.esa.int/Gaia transverse velocities means that only partial been evolving for 13 billion years in real dark 9. Parallax distances are so fundamental in astronomy that the basic distance unit is the parsec (pc), the distance of information can be modeled. Gaia will provide matter halos since they became gravitationally an object that displays a parallax of one second of arc. 1 precision transverse kinematic data, thus giv- bound, quantification of the relevant astro- pc = 3.26 light-years = 3.1016 m. ing access to reliable six-dimensional phase physics is also necessary. Despite the chal- space measures of location and speed for large lenges, real progress is being made, while dra- 10.1126/science.1165790 CHEMISTRY How does water meet a hydrophobic surface? Like great art, everyone recognizes A Curious Antipathy for Water hydrophobicity but few agree on the details. on December 8, 2008 Steve Granick and Sung Chul Bae magine that you are a water molecule at a ejected spontaneously, whereas water films without friction (3). Such water-filled nan- hydrophobic (water-repellent) surface. confined between symmetric hydrophilic otubes switch from hydrophobic at room tem- IGiven the chance, you would bead up with surfaces are stable (1). perature to hydrophilic when the temperature other water molecules to form a droplet, just Hydrophobicity shows up differently in is lowered to 8°C (4), in line with predictions as water beads up on raincoats or leaves of carbon nanotubes, within which a hydrogen- that a switch of this kind can happen because plants (see the figure, left panel). But what bonded chain of water molecules can form, the free energy of a full nanotube is very close www.sciencemag.org would you do if you were inside a droplet, yet stretching like a thread down the middle of to that of an empty nanotube (2). The obser- located very near the hydrophobic surface? the nanotube (see the figure, right panel) (2). vation opens the possibility that temperature Water molecules in this situation cannot leave The unusual hydrogen-bonding geometry may one day be used as a switch to make car- the surface although they would if they could; and nonstick surface result in flow essentially bon nanotubes selectively suck up chemicals they are frustrated. Such proximity of water to a hydrophobic surface is fundamental to the so-called hydrophobic effect. Its reasons are Downloaded from disputed, as is its definition. Not in dispute is its importance. For example, the side chains of roughly half the amino acids are polar, while those of the other half are hydrophobic; the nonmixing of the two is key to steering the folding of pro- teins and other self-assembly processes (see the figure, middle panel). As a second exam- ple, the fact that oil and water hardly mix is at the root of the self-assembly of supramolec- ular structures known as cell membranes (in biology) and micelles (in technology), where the self-assembling molecules contain both How water meets different hydrophobic elements. (Left) On flat planar self-assembled monolayers, the situation is simplest: The contact angle is high when the monolayer is terminated uniformly with CF groups, nonpolar and polar moieties. Furthermore, 3 when the gap between two hydrophobic and zero when it is terminated uniformly with OH groups. (Middle) The situation is more complex on the sur- face of a protein, α-chymotrypsin in this example. Hydrophobicity of the amino acid residues is weaker than surfaces becomes critically small, water is in the left panel, the size of the hydrophobic patch is smaller, and nothing is planar. For these reasons, the ten- dency to dewet is less than in the left panel. Water is predicted to envelop even the hydrophobic (green) patch Departments of Materials Science and Engineering, of amino acids, but likely with more fluctuation than at hydrophilic patches (1, 13). (Right) Water fills a car- Chemistry, and Physics, University of Illinois, Urbana, IL bon nanotube spontaneously, forming linear hydrogen-bonded threads of water running down the middle (2), CREDIT: SHEKHAR GARDE AND RAHUL GODAWAT/RENSSELAER POLYTECHNIC INSTITUTE POLYTECHNIC SHEKHAR GARDE AND RAHUL GODAWAT/RENSSELAER CREDIT: 61801, USA. E-mail: [email protected] yet the simultaneous tendency to dewet causes it to flow through the tube essentially without friction (3). www.sciencemag.org SCIENCE VOL 322 5 DECEMBER 2008 1477 Published by AAAS PERSPECTIVES like with a straw—not only water, but poten- face has the same wettability (hydrophobic or approach is to explain this in terms of the tially other solutes also (5). It also confirms hydrophilic) everywhere, or is “patchy” from hydrophobic effect (4), but it can also be the well-known weakening of hydrophobic spot to spot? Answers will bring understand- understood on the basis of more general prin- interactions upon cooling below room tem- ing in this field into closer contact with ciples of the competition between enthalpy perature (6). emerging issues in fields as diverse as protein and entropy (16). The challenge, then, is to Despite its obvious importance, physical folding and surface science. predict from theory, rather than from empiri- insight into the origins of hydrophobicity is not Second, scientists have concentrated on cism, what makes water so special. easy to come by. Thermodynamic mea- systems that are subject to steady external surements are one approach, but interpreting conditions, such as a low temperature that References and Notes their physical significance is extraordinarily causes proteins to denature. We do not yet 1. X. Zhang, Y. Zhu, S. Granick, Science 295, 663 (2002). 2. G. Hummer, J. C. Rasaiah, J. P. Noworyta, Nature 414, subtle (6). Theoretical considerations and com- have good ways to think about how aqueous 188 (2001). puter simulations show that a key concept is the systems respond to an extreme but perhaps 3. A. Kalra, S. Garde, G. Hummer, Proc. Natl. Acad. Sci. size of the hydrophobic object (7–9). Water transient change of environment. Is it realistic U.S.A. 100, 10175 (2003). molecules can wrap efficiently around hydro- to expect a general theory of hydrophobic sur- 4. H.-J. Wang, X.-K. Xi, A. Kleinhammes, Y. Wu, Science 322, 80 (2008). phobic elements with a radius of curvature of faces when temperature and pressure change 5. A. Kalra, G. Hummer, S. Garde, J. Phys. Chem. B 108, 1 nm or less. When water meets hydrophobic in time and space? Empiricism shows that 544 (2004). surfaces that are flatter than this, it forms a what matters is not just the instantaneous sep- 6. D. Ben-Amotz, B. Widom, J. Phys. Chem. B 110, 19839 (2006). molecularly thin cushion of depleted density aration between hydrophobic surfaces but 7. F. H. Stillinger, J. Sol. Chem. 2, 141 (1973). between it and the hydrophobic surface. also the time (or frequency) of their contact 8. K. Lum, D. Chandler, J. D. Weeks, J. Phys. Chem. B. 103, The fly in the ointment is experiment. (1); the timeline of change also matters. 4570 (1999). Putative depletion layers must fight against Third: When does water act truly unlike 9. J. Janecek, R. R. Netz, Langmuir 12, 8417 (2007). 10. A. Poynor et al., Phys. Rev. Lett. 97, 266101 (2006). attraction of water to any hydrophobic sur- other fluids? Spectroscopic studies of vibra- 11. A. Poynor et al., Phys. Rev. Lett. 101, 039602 (2008). face, a ubiquitous force known as van der tions in water molecules are a technical tour 12. M. Mezger et al., J. Chem. Phys. 128, 244705 (2008). Waals attraction. This is probably why labora- de force but are problematic to interpret (15). 13. K. Kashimoto et al., Phys. Rev. Lett. 101, 076102 tory data have provided evidence both for Prevalent computational models use point (2008). 14. D. Chandler, Nature 437, 640 (2005). on December 8, 2008 [(10, 11) and references therein; (12)] and charges and do not explicitly recognize quan- 15.
Load more

Recommended publications
  • Tsvi Tlusty – C.V
    TSVI TLUSTY – C.V. 06/2021 Center for Soft and Living Matter, Institute for Basic Science, Bldg. (#103), Ulsan National Institute of Science and Technology, 50 UNIST-gil, Ulju-gun, Ulsan 44919, Korea email: [email protected] homepage: life.ibs.re.kr EDUCATION AND EMPLOYMENT 2015– Distinguished Professor, Department of Physics, UNIST, Ulsan 2015– Group Leader, Center for Soft and Living Matter, Institute for Basic Science 2011–2015 Long-term Member, Institute of Advanced Study, Princeton. 2005–2013 Senior researcher, Physics of Complex Systems, Weizmann Institute. 2000–2004 Fellow, Center for Physics and Biology, Rockefeller University, New York. Host: Prof. Albert Libchaber 1995–2000 Ph.D. in Physics, Weizmann Institute, “Universality in Microemulsions”, Supervisor: Prof. Samuel A. Safran. 1991–1995 M.Sc. in Physics, Weizmann Institute. 1988–1990 B.Sc. in Physics and Mathematics (Talpyot), Hebrew University, Jerusalem. Teaching: Landmark Experiments in Biology (2006); Statistical Physics (2007, 2017-20); Information in Biology (2012); Errors and Codes (IAS, 2012); Theory of Living Matter (2016); Students and post-doctoral fellows (03/2020) Pineros William (postdoc, 2019- ) John Mcbride (postdoc, 2018- ) Somya Mani (postdoc, 2018- ) Tamoghna Das (postdoc, 2018- ) Ashwani Tripathi (postdoc, 2018- ) Sandipan Dutta (postdoc, 2016-2021), Prof. at BIRS Pileni, India Vladimir Reinharz (postdoc, 2018-2020), Prof. at U. Montreal. YongSeok Jho (research fellow, 2016-2017), Prof. at GyeongSang U. Yoni Savir (Ph.D., 2005-2011) Prof. at Technion. Adam Lampert (Ph.D., 2008-2012) Prof. at U. Arizona. Arbel Tadmor (M.Sc., 2006-2008) researcher at TRON. Maria Rodriguez Martinez (Postdoc, 2007-2009), PI at IBM Zurich Tamar Friedlander (Postdoc, 2009 -2012) Prof.
    [Show full text]
  • Catalytic Enzymes Are Active Matter
    View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by IBS Publications Repository Catalytic enzymes are active matter Ah-Young Jeea, Yoon-Kyoung Choa,b, Steve Granicka,c,d,1, and Tsvi Tlustya,c,1 aCenter for Soft and Living Matter, Institute for Basic Science, Ulsan 44919, South Korea; bDepartment of Biomedical Engineering, Ulsan National Institute of Science and Technology, Ulsan 44919, South Korea; cDepartment of Physics, Ulsan National Institute of Science and Technology, Ulsan 44919, South Korea; and dDepartment of Chemistry, Ulsan National Institute of Science and Technology, Ulsan 44919, South Korea Contributed by Steve Granick, September 27, 2018 (sent for review August 17, 2018; reviewed by Changbong Hyeon and Elisha Moses) Using a microscopic theory to analyze experiments, we demon- All this signaled a paradigm shift in our understanding of en- strate that enzymes are active matter. Superresolution fluores- zymes. Large-scale internal mobility, such as hinge-like rotations, cence measurements—performed across four orders of magnitude twists, or shear-like sliding, was already linked to the function of of substrate concentration, with emphasis on the biologically enzymes (9–13) in the classical mechanisms of allostery (14) and relevant regime around or below the Michaelis–Menten constant— induced fit (15). However, energetically driven translational mo- show that catalysis boosts the motion of enzymes to be superdif- tion was considered the exclusive realm of molecular motors (16). fusive for a few microseconds, enhancing their effective diffusiv- In light of the evidence for boosted enzymatic mobility, this dis- ity over longer timescales. Occurring at the catalytic turnover tinction appears rather artificial, and one should see enzymes as rate, these fast ballistic leaps maintain direction over a duration nanomotors whose dynamic profile influences their function and limited by rotational diffusion, driving enzymes to execute worm- spatiotemporal organization (3, 17–19).
    [Show full text]
  • Diffusing Wave Microrheology of Highly Scattering Concentrated Monodisperse Emulsions
    Diffusing wave microrheology of highly scattering concentrated monodisperse emulsions Ha Seong Kima, Nesrin S¸enbilb, Chi Zhangb, Frank Scheffoldb,1, and Thomas G. Masona,c,1 aDepartment of Chemistry and Biochemistry, University of California, Los Angeles, CA 90095; bDepartment of Physics, University of Fribourg, CH-1700 Fribourg, Switzerland; and cDepartment of Physics and Astronomy, University of California, Los Angeles, CA 90095 Edited by Steve Granick, IBS Center for Soft and Living Matter, Ulju-gun, Ulsan, Republic of Korea, and approved February 27, 2019 (received for review October 3, 2018) Motivated by improvements in diffusing wave spectroscopy nating light (4). Because the standard analytical framework of (DWS) for nonergodic, highly optically scattering soft matter and DWS neglects collective scattering of colloidal probes at high by cursory treatment of collective scattering effects in prior DWS densities, DWS MSDs extracted for such dense colloidal sys- microrheology experiments, we investigate the low-frequency tems do not necessarily represent the true self-motion of the 0 plateau elastic shear moduli Gp of concentrated, monodisperse, probes. Consequently, using DWS MSDs for thermal-entropic disordered oil-in-water emulsions as droplets jam. In such exper- passive microrheology (6, 7) of dense dispersions, including con- iments, the droplets play dual roles both as optical probes and centrated emulsions, would likely lead to inaccurate predictions as the jammed objects that impart shear elasticity. Here, we of their linear viscoelastic moduli, since passive microrheol- demonstrate that collective scattering significantly affects DWS ogy requires accurate self-motion MSDs in the generalized mean-square displacements (MSDs) in dense colloidal emulsions. Stokes–Einstein relation (GSER) (6, 8).
    [Show full text]
  • About the Authors
    1845 About the Authors Chong H. Ahn Chapter B.19 Authors University of Cincinnati Dr. Chong Ahn is a Professor of Electrical and Computer Engineering at the Department of Electrical University of Cincinnati. He obtained his Ph.D. degree in Electrical Engineering from and Computer Engineering the Georgia Institute of Technology in 1993 and then worked as a postdoctoral fellow and Computer Science at IBM T.J. Watson Research Center. His research interests include all aspects of Cincinnati, OH, USA [email protected] design, fabrication, and characterization of magnetic MEMS devices, microfluidic devices, protein chips, lab-on-a-chips, nano biosensors, point-of-care testing and BioMEMS systems. He is an associate editor of the IEEE Sensors Journal. Boris Anczykowski Chapter C.27 nanoAnalytics GmbH Dr. Boris Anczykowski is a physicist with an extensive research background in the Münster, Germany field of dynamic Scanning Force Microscopy. He co-invented the Q-Control technique [email protected] and received the Innovation Award Münsterland for Science and Economy in 2001 for this achievement. He is a managing director and co-founder of nanoAnalytics GmbH, a company specialized in the characterization of surfaces and interfaces on the micro- and nanometer scale. Massood Z. Atashbar Chapter A.7 Western Michigan University Professor Massood Z. Atashbar received the B.Sc. degree in electrical Department of Electrical engineering from the Isfahan University of Technology, Tehran, Iran, and Computer Engineering the M.Sc. degree in electrical engineering from the Sharif University of Kalamazoo, MI, USA Technology, Tehran, and the Ph.D. degree from the Department of [email protected] Communication and Electronic Engineering, RMIT University, Melbourne, Australia, in 1998.
    [Show full text]
  • Instructions for Preparation of Abstracts for UFO-HFSW 2009
    复旦大学物理系 物质科学报告 Time:2:00pm, Tuesday, 2020.01.14 Location: Room C108, Jiangwan Physics Building Title: Some Puzzles and Research Opportunities in Soft Matter Science Speaker: Steve Granick Director, Center for Soft and Living Matter Institute for Basic Science, South Korea Abstract: A fundamental challenge of modern physical science is to form structure that is not frozen in place but instead reconfigures internally driven by energy throughput and adapts to its environment robustly. Predicated on fluorescence imaging at the single-particle level and on liquid-cell TEM, this talk describes quantitative studies of how this can happen. With Janus colloidal clusters, we show the powerful role of synchronized motion in self-assembly. In living cells, we find that transportation efficiency problems bear a provocative parallel with polymer chain trajectories with their spatial extent, and with jammed matter in their time evolution. With catalytic enzymes, we find problems of mechanobiology. A picture emerges in which simple experiments, performed at single-particle and single-molecule resolution, can dissect macroscopic phenomena in ways that surprise. Steve Granick Member of the U.S. National Academy of Sciences Member of American Academy of Arts and Sciences. He received his PhD degree in University of Wisconsin in 1982. In 1982, he joined the French University of France and University of Minnesota for postdoctoral research. He became an professor in University of Illinois at Urbana-Champaigns. Since 2015, he became the director of the Laboratory at the Korea Institute of Basic Science in Soft Materials and Life Materials. Among his other major awards are the Paris-Sciences Medal, APS national Polymer Physics Prize, and ACS national Colloid and Surface Chemistry Prize..
    [Show full text]
  • PDF Download
    [Attachment 1-5] List of IBS Research Centers (As of Dec. 21, 2020) □ Total 31 Centers (30 Directors and 3 CIs) ○ Nine HQ, thirteen Campus(five at KAIST alliance campus, seven at DUP alliance campus, one at GIST), and nine Extramural Centers Field (number of Center name Director·CI Photo Center type Research area centers) Center for Correlated External Condensed NOH Tae Won Electron Systems (Seoul Nat. Univ.) matter physics Center for Integrated External Nanostructure LEE Young Hee Nanostructure Physics (Sungkyunkwan Univ.) physics Center for Relativistic Campus NAM Chang Hee Optics Laser Science (GIST) Center for Axion and Yannis Campus Elementary Precision Physics Research SEMERTZIDIS (KAIST) particle physics Center for Artificial YEOM Han Campus Condensed Low Dimensional Woong (POSTECH) matter physics Physics Electronic Systems (10) Center for KIM Yeongduk HQ Particle physics Underground Physics Ceter for Theoretical HQ Theoretical CHOI Kiwoon Physics of the Universe (Co-director) physics Center for Theoretical HQ Theoretical Physics of Complex Sergej FLACH (Co-director) physics Systems Center for Quantum Andreas External Quantum Nanoscience HEINRICH (Ewha W. Univ.) nanoscience Center for Exotic Rare Isotope HAHN Kevin Insik HQ Nuclear Studies Sciences SHIN Hee-Sup Center for Cognition HQ Brain science and Sociality LEE Changjoon (Co-director) Justin Center for Synaptic Campus KIM Eunjoon Brain science Brain Dysfunctions (KAIST) Life Center for RNA External Molecular cell KIM V. Narry Sciences Research (Seoul Nat. Univ.) biology (6)
    [Show full text]
  • Profile of Steve Granick PROFILE
    PROFILE Profile of Steve Granick PROFILE Sandeep Ravindran, Science Writer Steve Granick says a simple underlying principle—the Late Pivot to Natural desire for an interesting life with meaningful human Science relations—has guided his career. During undergradu- Granick dropped out of col- ate study at Princeton University, Granick majored in lege after his junior year as an sociology, mainly because he was interested in litera- undergraduate at Princeton ture, humanities, and social sciences. He took just one University. “I bummed around obligatory science class—introductory physics—and the [United States] taking odd found it so dry that he never took another one. De- jobs for three years,” he says. spite his initial lack of interest in science, Granick “One of those jobs turned out would go on to have a distinguished scientific career, to be ... in an oil field,” says eventually becoming director of the Institute for Basic Granick. “They were desperate Science (IBS) Center for Soft and Living Matter in for workers, so you would show Ulsan, South Korea, as well as being elected to the up and you would see this National Academy of Sciences in 2015. lighted derrick in the distance at “To me, research is like traveling the world. Some night—they called it the Christ- people like to visit a different country every few years, mas tree—andifyouhadtwo and I feel that way about scientific problems,” said hands and two feet, they would Granick. Working across disciplines, Granick’s wide- hire you. That was my introduc- ranging interests have led him to address the chemis- tion to lab work, and it turns out try and physics of everyday life, especially complex Ienjoyedit.” fluids, colloids, polymers, lipids, thin films, and bioma- Granick enjoyed this peri- terials.
    [Show full text]
  • Profile of Steve Granick
    PROFILE PROFILE Profile of Steve Granick Sandeep Ravindran, Science Writer Steve Granick says a simple underlying principle—the Granick’s latest scientific endeavor, described in desire for an interesting life with meaningful human re- his Inaugural Article (1), resulted in a surprising discov- lations—has guided his career. During undergraduate ery about how enzymes move, despite his laboratory study at Princeton University, Granick majored in sociol- never having worked on enzymes before. “Looking ogy, mainly because he was interested in literature, hu- back on it, nothing had changed,” says Granick. manities, and social sciences. He took just one obligatory “The actual world doesn’t know the difference be- science class—introductory physics—and found it so dry tween physics, chemistry, and social science; these that he never took another one. Despite his initial lack of distinctions are artificial,” he says. “I turned a taste interest in science, Granick would go on to have a dis- for exploration into a career in science, finding ways tinguished scientific career, eventually becoming direc- to avoid pigeonholing the lab’s research.” tor of the Institute for Basic Science (IBS) Center for Soft and Living Matter in Ulsan, South Korea, as well as being Late Pivot to Natural Science elected to the National Academy of Sciences in 2015. Granick dropped out of college after his junior year as an “To me, research is like traveling the world. Some undergraduate at Princeton University. “I bummed people like to visit a different country every few years, around the [United States] taking odd jobs for three and I feel that way about scientific problems,” said years,” he says.
    [Show full text]
  • Curriculum Vitae
    Curriculum Vitae Peter M. Hoffmann Professor of Physics and Astronomy Previous Senior Associate Dean College of Liberal Arts and Sciences Wayne State University Detroit, MI August 10, 2018 Contact Information Department of Physics Wayne State University 666 W Hancock St. Detroit, MI 48201 [email protected] Tel (mobile): 586-552-7019 Web: http://petermhoffmann.com Wayne State University is a comprehensive research institution in Midtown Detroit of about 27,000 students, with the largest single campus medical school in the country and a highly diverse body of students (>23% URM). It is one of the few institutions in the country enjoying both the Carnegie Highest research activity and Carnegie Community Engaged classifications. Positions Held August 2018 – present: Currently on leave from administrative duties (by choice). Working on research and completion of manuscripts and books and serve as co-lead of RCM budget cost allocation committee and as Co-PI on NSF IUSE grant on STEM teaching reform. August 2016 - August 2017: Senior Associate Dean of the College of Liberal Arts and Sciences (CLAS) Deputy dean of the college: Represented college in all functions in the absence of the Dean, including faculty hiring, alumni relations, budget issues, representation at Council of Deans, working with the Provost’s office. Peter M Hoffmann 1 August 2015 – August 2017: Associate Dean of Research, CLAS Responsible for all CLAS research activity across 20 departments with a total external funding portfolio of more than $16 Million/year. Continued development of CLAS research support structure. Supervisory role of CLAS research (an associate director and five departmental grant officers), CLAS web-team (an associate director and a webmaster) and IT and science research support (>10 employees).
    [Show full text]
  • Viewpoint Confined Liquid Controversies Near Closure?
    Physics 3, 73 (2010) Viewpoint Confined liquid controversies near closure? Steve Granick Departments of Materials Science and Engineering, Physics, and Chemistry, University of Illinois, Urbana, IL 61801, USA Sung Chul Bae, Subhalakshmi Kumar, and Changqian Yu Department of Materials Science and Engineering, University of Illinois, Urbana, IL 61801, USA Published August 30, 2010 New experiments resolve differences in measuring the viscosity of liquids confined to thin films at the molecular level. Subject Areas: Atomic and Molecular Physics, Soft Matter A Viewpoint on: Dynamic Solidification in Nanoconfined Water Films Shah H. Khan, George Matei, Shivprasad Patil, and Peter M. Hoffmann Physical Review Letters 105, 106101 2010 – Published August 30, 2010 Water excites intense controversy among researchers. the thickness is sufficiently small, the viscous losses pass Its crucial role in the natural and biological world is un- through a maximum and subsequently decrease. It is questioned but much of the agreement stops [1] when it worth noting that this behavior is characteristic of su- comes to details. In particular, how water behaves at percooled fluids when temperature is lowered or pressure interfaces is a central mystery. Some interfaces are hy- is raised. This study puts into perspective earlier studies drophobic [2], but here we are interested in polar surfaces, that seemed to contradict one another. Researchers who which attract water. This situation is common in the nat- concluded that confined water has an effective viscosity ural world, from earth and rock formations to buildings nearly the same as bulk water [4–6] and those who con- and highways, and also in the biological world, especially cluded otherwise [7–11] are now shown by Khan et al.
    [Show full text]
  • Exchange Kinetics Between the Adsorbed State and Free Solution: Poly(Methy1 Methacrylate) in Carbon Tetrachloride
    Macromolecules 1990,23, 3367-3374 3367 occur under dilute growth conditions. Quasielastic light (8) Martin, J. E.; Adolf, D.; Wilcoxon, J. P. Phys. Reo. Lett. 1988, scattering measurements then growth 61, 2620. (9) Martin, J. E.; Adolf, D.; Wilcoxon, J. p. Phys. Reu. A 1989, in time, as opposed to the critical growth observed close 39, 1325. to the gel Point. This exponentid growth and the observed (10) Durand, D.; Delsanti, M.; Adam, M.; Luck, J. M. Europhys. dimension of D = 2 indicate nonequilibrium cluster for- Lett. 1987, 3, 297. mation via reaction-limited aggregation. Thus different (11) Adolf, D.; Martin, J. E.; Wilcoxon, J. P. Macromolecules 1990, 23, 527. preparative pathways can be used to modify the strut- (12) de Gennes, P.-G. Scaling Concepts in Polymer Physics; Cor- ture of silica gels. ne11 University Press: Ithaca, NY, 1979. (13) Isaacson, J.; Lubensky, T. C. J. Phys. (Paris) 1980, 41, L469. References and Notes (14) de Gennes, P.-G. J. Phys. (Paris) 1979,40, L197. (15) Martin. J. E. J. Phvs. A: Math. Gen. 1985. 18. L207. (16) Martin; J. E.; Ackerson, B. J. Phys. Reu.'A 1985, 31, 1180. Martin, J. E. In Time-Dependent Effects in Disordered See also: Martin, J. E. J. Appl. Crystallogr. 1986, 19, 25. Materials; Pynn, R., Riste, T., Eds.; Plenum: New York, 1988. (17) Daoud, M.; Martin, J. E. In The Fractal Approach to Heter- Martin, J. E.; Keefer, K. D. Phys. Reu. A 1986, 34, 4988. ogeneous Chemistry: Surfaces, Colloids, Polymers;Avnir, D., Dubois, M.; Cabane, B. Macromolecules 1989,22, 2526.
    [Show full text]
  • Matt Tirrell
    .,~•• 5_§._e_d...:.u_c_a_t_o_r __________) Minnesota's MATT TIRRELL Matt and teaching assistant Rafael Galvan demonstrating nylon polymerization during a poly­ mer chemistry lecture. Galvan, now at Dow Chemical, coauthored Polymerization Process Model­ ing with Matt, Neil Dotson (Eastman Chemical), and Bob Lawrence (University of Massachusetts). W RITTEN BY HIS COLLEAGUES University of Minnesota • Minneapolis, MN 55455 n a department that has been home to such chemical 1995, and in so doing he added one more huge responsibility engineering legends as Neil Amundson, Rutherford Aris, to his shoulders, but he did it without neglecting his other I and Skip Scriven, Matt Tirrell has carved out a niche for duties as scholar, teacher, mentor, editor, and researcher. His himself as a modern-day Renaissance Man. Applying a no­ colleagues are justifiably amazed and proud of his diversity tably broad knowledge of chemical engineering and materi­ and leadership. als science to a mulligan stew of engineering research, he is Matt was born September 5, 1950, in Phillipsburg, New a marked asset to a department emphasizing collegiality and Jersey, on the Delaware River border with Pennsylvania, a team-teaching philosophy. and is the oldest of three children. His younger brother, Abundant energy and a gift for organization allow Matt to Dave, also developed a strong interest in polymer chemistry keep multiple and varied projects moving forward at the and is currently Professor of Chemistry and Chemical Engi­ same time. After 18 years of making a name for himself, neering at Caltech. The youngest sibling, Mary, is raising Matt took the reins of the Chemical Engineering and Materi­ three children in Bangor, Pennsylvania, close to Phillipsburg, als Science Department at the University of Minnesota in and helps in her husband's construction business in addition © Copyright ChE Division of ASEE 1998 162 Chemical Engineering Education • Matthew V.
    [Show full text]