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Holt AP, Roland CM. Segmental and secondary dynamics of nanoparticle-grafted oligomers. SOFT MATTER 2018; 14:8604-8611. [PMID: 30318533 DOI: 10.1039/c8sm01443d] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The local segmental and secondary dynamics of tetramethylene oxide oligomer grafted to silica nanoparticles (NPs) were investigated as a function of grafting density and molecular weight. Grafting slows the segmental (α) dynamics, but gives rise to faster secondary (β) motions. Interestingly, the magnitude of these effects decreases with the extent of grafting (i.e., surface coverage), as well as with oligomer molecular weight. The disparity in dynamical effects reflects the decoupling of the segmental and more local β dynamics, the former is associated with stronger dynamic correlations that extend over a greater spatial range. This results in greater sensitivity to interactions, including tethering of the chains to the NP surface.
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Affiliation(s)
- Adam P Holt
- Chemistry Division, Naval Research Laboratory, Code 6105, Washington, DC 20375-5342, USA.
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Zhang P, Maldonis JJ, Liu Z, Schroers J, Voyles PM. Spatially heterogeneous dynamics in a metallic glass forming liquid imaged by electron correlation microscopy. Nat Commun 2018; 9:1129. [PMID: 29555920 PMCID: PMC5859095 DOI: 10.1038/s41467-018-03604-2] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2017] [Accepted: 02/25/2018] [Indexed: 11/08/2022] Open
Abstract
Supercooled liquids exhibit spatial heterogeneity in the dynamics of their fluctuating atomic arrangements. The length and time scales of the heterogeneous dynamics are central to the glass transition and influence nucleation and growth of crystals from the liquid. Here, we report direct experimental visualization of the spatially heterogeneous dynamics as a function of temperature in the supercooled liquid state of a Pt-based metallic glass, using electron correlation microscopy with sub-nanometer resolution. An experimental four-point space-time correlation function demonstrates a growing dynamic correlation length, ξ, upon cooling of the liquid toward the glass transition temperature. ξ as a function of the relaxation time τ are in good agreement with Adam-Gibbs theory, inhomogeneous mode-coupling theory and random first-order transition theory of the glass transition. The same experiments demonstrate the existence of a nanometer thickness near-surface layer with order of magnitude shorter relaxation time than inside the bulk.
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Affiliation(s)
- Pei Zhang
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Jason J Maldonis
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Ze Liu
- Department of Mechanical Engineering and Materials Science, Yale University, New Haven, CT, 06511, USA
| | - Jan Schroers
- Department of Mechanical Engineering and Materials Science, Yale University, New Haven, CT, 06511, USA
| | - Paul M Voyles
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA.
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Gupta S, Fischer JKH, Lunkenheimer P, Loidl A, Novak E, Jalarvo N, Ohl M. Effect of adding nanometre-sized heterogeneities on the structural dynamics and the excess wing of a molecular glass former. Sci Rep 2016; 6:35034. [PMID: 27725747 PMCID: PMC5057163 DOI: 10.1038/srep35034] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2016] [Accepted: 09/21/2016] [Indexed: 11/17/2022] Open
Abstract
We present the relaxation dynamics of glass-forming glycerol mixed with 1.1 nm sized polyhedral oligomeric silsesquioxane (POSS) molecules using dielectric spectroscopy (DS) and two different neutron scattering (NS) techniques. Both, the reorientational dynamics as measured by DS and the density fluctuations detected by NS reveal a broadening of the α relaxation when POSS molecules are added. Moreover, we find a significant slowing down of the α-relaxation time. These effects are in accord with the heterogeneity scenario considered for the dynamics of glasses and supercooled liquids. The addition of POSS also affects the excess wing in glycerol arising from a secondary relaxation process, which seems to exhibit a dramatic increase in relative strength compared to the α relaxation.
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Affiliation(s)
- S Gupta
- Juelich Centre for Neutron science (JCNS) outstation at SNS, POB 2008, 1 Bethel Valley Road, TN 37831, Oak Ridge, USA.,Biology and Soft Matter Division, Neutron Sciences Directorate, Oak Ridge National Laboratory (ORNL), POB 2008, 1 Bethel Valley Road, TN 37831, Oak Ridge, USA.,Department of Chemistry and Macromolecular Studies Group, Louisiana State University, Baton Rouge, LA 70803, USA
| | - J K H Fischer
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86135 Augsburg, Germany
| | - P Lunkenheimer
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86135 Augsburg, Germany
| | - A Loidl
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86135 Augsburg, Germany
| | - E Novak
- Department of Materials Science and Engineering, University of Tennessee, Knoxville, TN 37996, USA
| | - N Jalarvo
- Juelich Centre for Neutron science (JCNS) outstation at SNS, POB 2008, 1 Bethel Valley Road, TN 37831, Oak Ridge, USA.,Chemical and Engineering Materials Division, Oak Ridge National Laboratory (ORNL), PO BOX 2008 MS6473, TN 37831, Oak Ridge, USA
| | - M Ohl
- Juelich Centre for Neutron science (JCNS) outstation at SNS, POB 2008, 1 Bethel Valley Road, TN 37831, Oak Ridge, USA.,Biology and Soft Matter Division, Neutron Sciences Directorate, Oak Ridge National Laboratory (ORNL), POB 2008, 1 Bethel Valley Road, TN 37831, Oak Ridge, USA
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