1
|
Arya V, Chaudhuri A, Bakli C. Wettability-modulated behavior of polymers under varying degrees of nano-confinement. J Chem Phys 2024; 160:064905. [PMID: 38341795 DOI: 10.1063/5.0185533] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2023] [Accepted: 01/15/2024] [Indexed: 02/13/2024] Open
Abstract
Extreme confinement in nanochannels results in unconventional equilibrium and flow behavior of polymers. The underlying flow physics dictating such paradigms remains far from being understood and more so if the confining substrate is composed of two-dimensional materials, such as graphene. In this study, we conducted systematic molecular dynamics simulations to explore the effect of wettability, confinement, and chain length on polymer flow through graphene-like nanochannels. Altering the wetting properties of these membranes that structurally represent graphene results in substantial changes in the behavior of polymers of disparate chain lengths. Longer hydrocarbon chains (n-dodecane) exhibit negligible wettability-dependent structuring in narrower nanochannels compared to shorter chains (n-hexane) culminating in higher average velocities and interfacial slippage of n-dodecane under less wettable conditions. We demonstrate that the wettability compensation comes from chain entanglement attributed to entropic factors. This study reveals a delicate balance between wettability-dependent enthalpy and chain-length-dependent entropy, resulting in a unique nanoscale flow paradigm, thus not only having far-reaching implications in the superior discernment of polymeric flow in sub-micrometer regimes but also potentially revolutionizing various applications in the oil industry, including innovative oil transport, oil extraction, ion transport polymers, and separation membranes.
Collapse
Affiliation(s)
- Vinay Arya
- Thermofluidics and Nanotechnology for Sustainable Energy Systems Laboratory, School of Energy Science and Engineering, Indian Institute of Technology Kharagpur, Kharagpur 721302, India
| | - Abhirup Chaudhuri
- Department of Mechanical Engineering, Indian Institute of Technology Kharagpur, Kharagpur 721302, India
| | - Chirodeep Bakli
- Thermofluidics and Nanotechnology for Sustainable Energy Systems Laboratory, School of Energy Science and Engineering, Indian Institute of Technology Kharagpur, Kharagpur 721302, India
| |
Collapse
|
2
|
Thoms E, Napolitano S. Enthalpy-entropy compensation in the slow Arrhenius process. J Chem Phys 2023; 159:161103. [PMID: 37888759 DOI: 10.1063/5.0174213] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2023] [Accepted: 10/02/2023] [Indexed: 10/28/2023] Open
Abstract
The Meyer-Neldel compensation law, observed in a wide variety of chemical reactions and other thermally activated processes, provides a proportionality between the entropic and the enthalpic components of an energy barrier. By analyzing 31 different polymer systems, we show that such an intriguing behavior is encountered also in the slow Arrhenius process, a recently discovered microscopic relaxation mode, responsible for several equilibration mechanisms both in the liquid and the glassy state. We interpret this behavior in terms of the multiexcitation entropy model, indicating that overcoming large energy barriers can require a high number of low-energy local excitations, providing a multiphonon relaxation process.
Collapse
Affiliation(s)
- Erik Thoms
- Laboratory of Polymer and Soft Matter Dynamics, Experimental Soft Matter and Thermal Physics (EST), Université libre de Bruxelles (ULB), Brussels 1050, Belgium
| | - Simone Napolitano
- Laboratory of Polymer and Soft Matter Dynamics, Experimental Soft Matter and Thermal Physics (EST), Université libre de Bruxelles (ULB), Brussels 1050, Belgium
| |
Collapse
|
3
|
Tawade BV, Singh M, Apata IE, Veerasamy J, Pradhan N, Karim A, Douglas JF, Raghavan D. Polymer-Grafted Nanoparticles with Variable Grafting Densities for High Energy Density Polymeric Nanocomposite Dielectric Capacitors. JACS AU 2023; 3:1365-1375. [PMID: 37234129 PMCID: PMC10207098 DOI: 10.1021/jacsau.3c00022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/10/2023] [Revised: 04/11/2023] [Accepted: 04/13/2023] [Indexed: 05/27/2023]
Abstract
Designing high energy density dielectric capacitors for advanced energy storage systems needs nanocomposite-based dielectric materials, which can utilize the properties of both inorganic and polymeric materials. Polymer-grafted nanoparticle (PGNP)-based nanocomposites alleviate the problems of poor nanocomposite properties by providing synergistic control over nanoparticle and polymer properties. Here, we synthesize "core-shell" barium titanate-poly(methyl methacrylate) (BaTiO3-PMMA) grafted PGNPs using surface-initiated atom transfer polymerization (SI-ATRP) with variable grafting densities of (0.303 to 0.929) chains/nm2 and high molecular masses (97700 g/mL to 130000 g/mol) and observe that low grafted density and high molecular mass based PGNP show high permittivity, high dielectric strength, and hence higher energy densities (≈ 5.2 J/cm3) as compared to the higher grafted density PGNPs, presumably due to their "star-polymer"-like conformations with higher chain-end densities that are known to enhance breakdown. Nonetheless, these energy densities are an order of magnitude higher than their nanocomposite blend counterparts. We expect that these PGNPs can be readily used as commercial dielectric capacitors, and these findings can serve as guiding principles for developing tunable high energy density energy storage devices using PGNP systems.
Collapse
Affiliation(s)
- Bhausaheb V. Tawade
- Department
of Chemistry, Howard University, Washington, D.C. 20059, United States
| | - Maninderjeet Singh
- Department
of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204, United States
| | - Ikeoluwa E. Apata
- Department
of Chemistry, Howard University, Washington, D.C. 20059, United States
| | - Jagadesh Veerasamy
- Department
of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204, United States
| | - Nihar Pradhan
- Department
of Chemistry, Physics and Atmospheric Science, Jackson State University, Jackson, Mississippi 39217, United States
| | - Alamgir Karim
- Department
of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204, United States
| | - Jack F. Douglas
- Material
Science and Engineering Division, National
Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
| | - Dharmaraj Raghavan
- Department
of Chemistry, Howard University, Washington, D.C. 20059, United States
| |
Collapse
|
4
|
Cordella G, Tripodo A, Puosi F, Pisignano D, Leporini D. Nanoscale Elastoplastic Wrinkling of Ultrathin Molecular Films. Int J Mol Sci 2021; 22:11732. [PMID: 34769167 PMCID: PMC8583903 DOI: 10.3390/ijms222111732] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2021] [Revised: 10/20/2021] [Accepted: 10/25/2021] [Indexed: 11/25/2022] Open
Abstract
Ultrathin molecular films deposited on a substrate are ubiquitously used in electronics, photonics, and additive manufacturing methods. The nanoscale surface instability of these systems under uniaxial compression is investigated here by molecular dynamics simulations. We focus on deviations from the homogeneous macroscopic behavior due to the discrete, disordered nature of the deformed system, which might have critical importance for applications. The instability, which develops in the elastoplastic regime above a finite critical strain, leads to the growth of unidimensional wrinkling up to strains as large as 0.5. We highlight both the dominant wavelength and the amplitude of the wavy structure. The wavelength is found to scale geometrically with the film length, λ∝L, up to a compressive strain of ε≃0.4 at least, depending on the film length. The onset and growth of the wrinkling under small compression are quite well described by an extended version of the familiar square-root law in the strain ε observed in macroscopic systems. Under large compression (ε≳0.25), we find that the wrinkling amplitude increases while leaving the cross section nearly constant, offering a novel interpretation of the instability with a large amplitude. The contour length of the film topography is not constant under compression, which is in disagreement with the simple accordion model. These findings might be highly relevant for the design of novel and effective wrinkling and buckling patterns and architectures in flexible platforms for electronics and photonics.
Collapse
Affiliation(s)
- Gianfranco Cordella
- Dipartimento di Fisica “Enrico Fermi”, Università di Pisa, Largo B.Pontecorvo 3, I-56127 Pisa, Italy; (G.C.); (A.T.); (F.P.); (D.P.)
| | - Antonio Tripodo
- Dipartimento di Fisica “Enrico Fermi”, Università di Pisa, Largo B.Pontecorvo 3, I-56127 Pisa, Italy; (G.C.); (A.T.); (F.P.); (D.P.)
| | - Francesco Puosi
- Dipartimento di Fisica “Enrico Fermi”, Università di Pisa, Largo B.Pontecorvo 3, I-56127 Pisa, Italy; (G.C.); (A.T.); (F.P.); (D.P.)
- Istituto Nazionale di Fisica Nucleare (INFN), Sezione di Pisa, Largo B.Pontecorvo 3, I-56127 Pisa, Italy
| | - Dario Pisignano
- Dipartimento di Fisica “Enrico Fermi”, Università di Pisa, Largo B.Pontecorvo 3, I-56127 Pisa, Italy; (G.C.); (A.T.); (F.P.); (D.P.)
- NEST, Istituto Nanoscienze-CNR, Piazza S. Silvestro 12, I-56127 Pisa, Italy
| | - Dino Leporini
- Dipartimento di Fisica “Enrico Fermi”, Università di Pisa, Largo B.Pontecorvo 3, I-56127 Pisa, Italy; (G.C.); (A.T.); (F.P.); (D.P.)
- Istituto per i Processi Chimico-Fisici-Consiglio Nazionale delle Ricerche (IPCF-CNR), Via G. Moruzzi 1, I-56124 Pisa, Italy
| |
Collapse
|
5
|
Masud A, Wu W, Singh M, Tonny W, Ammar A, Sharma K, Strzalka JW, Terlier T, Douglas JF, Karim A. Solvent Processing and Ionic Liquid-Enabled Long-Range Vertical Ordering in Block Copolymer Films with Enhanced Film Stability. Macromolecules 2021. [DOI: 10.1021/acs.macromol.1c01305] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Affiliation(s)
- Ali Masud
- Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204, United States
| | - Wenjie Wu
- Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204, United States
| | - Maninderjeet Singh
- Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204, United States
| | - Wafa Tonny
- Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204, United States
| | - Ali Ammar
- Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204, United States
| | - Kshitij Sharma
- Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204, United States
| | - Joseph W. Strzalka
- X-Ray Science Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Tanguy Terlier
- Shared Equipment Authority, Rice University, 6100 Main Street, Houston, Texas 77005, United States
| | - Jack F. Douglas
- Materials Engineering Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
| | - Alamgir Karim
- Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204, United States
| |
Collapse
|
6
|
Bhadauriya S, Nallapaneni A, Wang X, Zhang J, Masud A, Bockstaller MR, Al-Enizi AM, Stafford CM, Douglas JF, Karim A. Enhanced resistance to decay of imprinted nanopatterns in thin films by bare nanoparticles compared to polymer-grafted nanoparticles. NANOSCALE ADVANCES 2021; 3:5348-5354. [PMID: 36132626 PMCID: PMC9419356 DOI: 10.1039/d1na00206f] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/19/2021] [Accepted: 07/16/2021] [Indexed: 06/15/2023]
Abstract
We extend a previous study on the influence of nanoparticles on the decay of nanoimprinted polymer film patterns to compare the effects of "bare" silica (SiO2) nanoparticles and SiO2 nanoparticles with grafted polymer layers having the same chemical composition as the polymer matrix. This method involves nanoimprinting substrate-supported polymer films using a pattern replicated from a digital versatile disc (DVD), and then annealing the patterned polymer nanocomposite films at elevated temperatures to follow the decay of the topographic surface pattern with time by atomic force microscopy imaging after quenching. We quantified the relaxation of the pattern height ("slumping") and determined the relaxation time τ for this pattern decay process as a function of nanoparticle filler type and concentration to determine how nanoparticle additives influence relative film stability. Attractive interactions between the bare nanoparticles and the polymer matrix significantly enhance the thermal resilience of the nanopatterns to decay, compared to those of the particle brushes, wherein the particle core interactions are screened from the matrix via the brush layer. A novel aspect of this method is that it readily lends itself to in situ film relaxation measurements in a manufacturing context. We observe that the relaxation time of the pattern relaxation exhibits entropy-enthalpy compensation in the free energy parameters governing the pattern relaxation process as a function of temperature, irrespective of the NP system used, consistent with our previous experimental and computational studies.
Collapse
Affiliation(s)
- Sonal Bhadauriya
- Department of Polymer Engineering, University of Akron Akron Ohio 44325 USA
| | | | - Xiaoteng Wang
- Department of Polymer Engineering, University of Akron Akron Ohio 44325 USA
| | - Jianan Zhang
- Department of Materials Science and Engineering, Carnegie Mellon University Pittsburgh Pennsylvania 15213 USA
| | - Ali Masud
- Department of Chemical and Biomolecular Engineering, University of Houston Houston Texas 77204 USA
| | - Michael R Bockstaller
- Department of Materials Science and Engineering, Carnegie Mellon University Pittsburgh Pennsylvania 15213 USA
| | - Abdullah M Al-Enizi
- Department of Chemistry, College of Science, King Saud University Riyadh 11451 Saudi Arabia
| | - Christopher M Stafford
- Materials Science and Engineering Division, National Institute of Standards and Technology Gaithersburg Maryland 20899 USA
| | - Jack F Douglas
- Materials Science and Engineering Division, National Institute of Standards and Technology Gaithersburg Maryland 20899 USA
| | - Alamgir Karim
- Department of Chemical and Biomolecular Engineering, University of Houston Houston Texas 77204 USA
| |
Collapse
|
7
|
Wu W, Singh M, Masud A, Wang X, Nallapaneni A, Xiao Z, Zhai Y, Wang Z, Terlier T, Bleuel M, Yuan G, Satija SK, Douglas JF, Matyjaszewski K, Bockstaller MR, Karim A. Control of Phase Morphology of Binary Polymer Grafted Nanoparticle Blend Films via Direct Immersion Annealing. ACS NANO 2021; 15:12042-12056. [PMID: 34255492 DOI: 10.1021/acsnano.1c03357] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
While the phase separation of binary mixtures of chemically different polymer-grafted nanoparticles (PGNPs) is observed to superficially resemble conventional polymer blends, the presence of a "soft" polymer-grafted layer on the inorganic core of these nanoparticles qualitatively alters the phase separation kinetics of these "nanoblends" from the typical pattern of behavior seen in polymer blends and other simple fluids. We investigate this system using a direct immersion annealing method (DIA) that allows for a facile tuning of the PGNPs phase boundary, phase separation kinetics, and the ultimate scale of phase separation after a sufficient "aging" time. In particular, by switching the DIA solvent composition from a selective one (which increases the interaction parameter according to Timmerman's rule) to an overall good solvent for both PGNP components, we can achieve rapid switchability between phase-separated and homogeneous states. Despite a relatively low and non-classical power-law coarsening exponent, the overall phase separation process is completed on a time scale on the order of a few minutes. Moreover, the roughness of the PGNP blend film saturates at a scale that is proportional to the in-plane phase separation pattern scale, as observed in previous blend and block copolymer film studies. The relatively low magnitude of the coarsening exponent n is attributed to a suppression of hydrodynamic interactions between the PGNPs. The DIA method provides a significant opportunity to control the phase separation morphology of PGNP blends by solution processing, and this method is expected to be quite useful in creating advanced materials.
Collapse
Affiliation(s)
- Wenjie Wu
- Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204, United States
| | - Maninderjeet Singh
- Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204, United States
| | - Ali Masud
- Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204, United States
| | - Xiaoteng Wang
- Department of Polymer Engineering, University of Akron, Akron, Ohio 44325, United States
| | - Asritha Nallapaneni
- Department of Polymer Engineering, University of Akron, Akron, Ohio 44325, United States
| | - Zihan Xiao
- Department of Materials Science and Engineering, University of Houston, Houston, Texas 77204, United States
| | - Yue Zhai
- Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States
| | - Zongyu Wang
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States
| | - Tanguy Terlier
- SIMS Laboratory, Shared Equipment Authority, Rice University, Houston, Texas 77005, United States
| | - Markus Bleuel
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
| | - Guangcui Yuan
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
| | - Sushil K Satija
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
| | - Jack F Douglas
- Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
| | - Krzysztof Matyjaszewski
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States
| | - Michael R Bockstaller
- Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States
| | - Alamgir Karim
- Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204, United States
| |
Collapse
|
8
|
Griessen R, Dam B. Simple Accurate Verification of Enthalpy-Entropy Compensation and Isoequilibrium Relationship. Chemphyschem 2021; 22:1774-1784. [PMID: 34213060 PMCID: PMC8456872 DOI: 10.1002/cphc.202100431] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2021] [Revised: 06/30/2021] [Indexed: 11/16/2022]
Abstract
In many experimental investigations of thermodynamic equilibrium or kinetic properties of series of similar reactions it is found that the enthalpies and entropies derived from Van ′t Hoff or Arrhenius plots exhibit a strong linear correlation. The origin of this Enthalpy‐Entropy compensation, which is strongly related to the coalescence tendency of Van ′t Hoff or Arrhenius plots, is not necessarily due to a physical/chemical/biological process. It can also be a merely statistical artefact. A new method, called Combined K‐CQF makes it possible both to quantify the degree of coalescence of experimental Van ‘t Hoff lines and to verify whether or not the Enthalpy‐Entropy Compensation is of a statistical origin at a desired confidence level. The method is universal and can handle data sets with any degree of coalescence of Van ‘t Hoff (or Arrhenius) plots. The new method requires only a standard least square fit of the enthalpyΔH versus entropy ΔS plot to determine the two essential dimensionless parameters K and CQF. The parameter K indicates the position (in inverse temperature) of the coalescence region of Van ‘t Hoff plots and CQF is a quantitative measure of the smallest spread of the Van ‘t Hoff plots. The position of the (K, CQF) couple with respect to universal confidence contours determined from a large number of simulations of random Van ‘t Hoff plots indicates straightforwardly whether or not the ΔH‐ΔS compensation is a statistical artefact.
Collapse
Affiliation(s)
- Ronald Griessen
- Condensed Matter Physics, Faculty of Sciences, VU University Amsterdam, De Boelelaan, 1081, 1081 HV, Amsterdam, The, Netherlands
| | - Bernard Dam
- Materials for Energy Conversion and Storage, Department of Chemical Engineering, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629 HZ, Delft, The, Netherlands
| |
Collapse
|
9
|
Masud A, Longanecker M, Bhadauriya S, Singh M, Wu W, Sharma K, Terlier T, Al-Enizi AM, Satija S, Douglas JF, Karim A. Ionic Liquid Enhanced Parallel Lamellar Ordering in Block Copolymer Films. Macromolecules 2021. [DOI: 10.1021/acs.macromol.0c02546] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Affiliation(s)
- Ali Masud
- Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204-4004, United States
| | - Melanie Longanecker
- Department of Polymer Engineering, The University of Akron, Akron, Ohio 44325, United States
| | | | - Maninderjeet Singh
- Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204-4004, United States
| | - Wenjie Wu
- Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204-4004, United States
| | - Kshitij Sharma
- Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204-4004, United States
| | - Tanguy Terlier
- SIMS Laboratory, Shared Equipment Authority, Rice University, 6100 Main Street, Houston, Texas 77005-1892, United States
| | - Abdullah M. Al-Enizi
- Department of Chemistry, College of Science, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia
| | - Sushil Satija
- Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-3460, United States
| | - Jack F. Douglas
- Materials Engineering Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-3460, United States
| | - Alamgir Karim
- Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204-4004, United States
| |
Collapse
|
10
|
Liu AY, Emamy H, Douglas JF, Starr FW. Effects of Chain Length on the Structure and Dynamics of Semidilute Nanoparticle–Polymer Composites. Macromolecules 2021. [DOI: 10.1021/acs.macromol.0c02500] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Ari Y. Liu
- Department of Physics, Wesleyan University, Middletown, Connecticut 06459, United States
| | - Hamed Emamy
- Department of Physics, Wesleyan University, Middletown, Connecticut 06459, United States
- Department of Chemical Engineering, Columbia University, New York, New York 10027, United States
| | - Jack F. Douglas
- Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
| | - Francis W. Starr
- Department of Physics, Wesleyan University, Middletown, Connecticut 06459, United States
| |
Collapse
|