Relaxation Dynamics of Nanoparticle-Tethered Polymer Chains

Handle URI:
http://hdl.handle.net/10754/599493
Title:
Relaxation Dynamics of Nanoparticle-Tethered Polymer Chains
Authors:
Kim, Sung A; Mangal, Rahul; Archer, Lynden A.
Abstract:
© 2015 American Chemical Society. Relaxation dynamics of nanoparticle-tethered cis-1,4-polyisoprene (PI) are investigated using dielectric spectroscopy and rheometry. A model system composed of polymer chains densely grafted to spherical SiO2 nanoparticles to form self-suspended suspensions facilitates detailed studies of slow global chain and fast segmental mode dynamics under surface and geometrical confinement-from experiments performed in bulk materials. We report that unentangled polymer molecules tethered to nanoparticles relax far more slowly than their tethered entangled counterparts. Specifically, at fixed grafting density we find, counterintuitively, that increasing the tethered polymer molecular weight up to values close to the entanglement molecular weight speeds up chain relaxation dynamics. Decreasing the polymer grafting density for a fixed molecular weight has the opposite effect: it dramatically slows down chain relaxation, increases interchain coupling, and leads to a transition in rheological response from simple fluid behavior to viscoelastic fluid behavior for tethered PI chains that are unentangled by conventional measures. Increasing the measurement temperature produces an even stronger elastic response and speeds up molecular relaxation at a rate that decreases with grafting density and molecular weight. These observations are discussed in terms of chain confinement driven by crowding between particles and by the existence of an entropic attractive force produced by the space-filling constraint on individual chains in a self-suspended material. Our results indicate that the entropic force between densely grafted polymer molecules couples motions of individual chains in an analogous manner to reversible cross-links in associating polymers.
Citation:
Kim SA, Mangal R, Archer LA (2015) Relaxation Dynamics of Nanoparticle-Tethered Polymer Chains. Macromolecules 48: 6280–6293. Available: http://dx.doi.org/10.1021/acs.macromol.5b00791.
Publisher:
American Chemical Society (ACS)
Journal:
Macromolecules
KAUST Grant Number:
KUS-C1-018-02
Issue Date:
8-Sep-2015
DOI:
10.1021/acs.macromol.5b00791
Type:
Article
ISSN:
0024-9297; 1520-5835
Sponsors:
This work was supported by the National Science Foundation Award No. DMR-1006323 and by Award No. KUS-C1-018-02 made by King Abdullah University of Science and Technology (KAUST). Facilities available though the Cornell Center for Materials Research (CCMR) were used for this study (DMR-1120296). Use of the Advanced Photon Source, operated by the Argonne National Laboratory, was supported by the US DOE under Contract No. DE–AC02–06CH11357.
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Full metadata record

DC FieldValue Language
dc.contributor.authorKim, Sung Aen
dc.contributor.authorMangal, Rahulen
dc.contributor.authorArcher, Lynden A.en
dc.date.accessioned2016-02-28T05:52:09Zen
dc.date.available2016-02-28T05:52:09Zen
dc.date.issued2015-09-08en
dc.identifier.citationKim SA, Mangal R, Archer LA (2015) Relaxation Dynamics of Nanoparticle-Tethered Polymer Chains. Macromolecules 48: 6280–6293. Available: http://dx.doi.org/10.1021/acs.macromol.5b00791.en
dc.identifier.issn0024-9297en
dc.identifier.issn1520-5835en
dc.identifier.doi10.1021/acs.macromol.5b00791en
dc.identifier.urihttp://hdl.handle.net/10754/599493en
dc.description.abstract© 2015 American Chemical Society. Relaxation dynamics of nanoparticle-tethered cis-1,4-polyisoprene (PI) are investigated using dielectric spectroscopy and rheometry. A model system composed of polymer chains densely grafted to spherical SiO2 nanoparticles to form self-suspended suspensions facilitates detailed studies of slow global chain and fast segmental mode dynamics under surface and geometrical confinement-from experiments performed in bulk materials. We report that unentangled polymer molecules tethered to nanoparticles relax far more slowly than their tethered entangled counterparts. Specifically, at fixed grafting density we find, counterintuitively, that increasing the tethered polymer molecular weight up to values close to the entanglement molecular weight speeds up chain relaxation dynamics. Decreasing the polymer grafting density for a fixed molecular weight has the opposite effect: it dramatically slows down chain relaxation, increases interchain coupling, and leads to a transition in rheological response from simple fluid behavior to viscoelastic fluid behavior for tethered PI chains that are unentangled by conventional measures. Increasing the measurement temperature produces an even stronger elastic response and speeds up molecular relaxation at a rate that decreases with grafting density and molecular weight. These observations are discussed in terms of chain confinement driven by crowding between particles and by the existence of an entropic attractive force produced by the space-filling constraint on individual chains in a self-suspended material. Our results indicate that the entropic force between densely grafted polymer molecules couples motions of individual chains in an analogous manner to reversible cross-links in associating polymers.en
dc.description.sponsorshipThis work was supported by the National Science Foundation Award No. DMR-1006323 and by Award No. KUS-C1-018-02 made by King Abdullah University of Science and Technology (KAUST). Facilities available though the Cornell Center for Materials Research (CCMR) were used for this study (DMR-1120296). Use of the Advanced Photon Source, operated by the Argonne National Laboratory, was supported by the US DOE under Contract No. DE–AC02–06CH11357.en
dc.publisherAmerican Chemical Society (ACS)en
dc.titleRelaxation Dynamics of Nanoparticle-Tethered Polymer Chainsen
dc.typeArticleen
dc.identifier.journalMacromoleculesen
dc.contributor.institutionCornell University, Ithaca, United Statesen
kaust.grant.numberKUS-C1-018-02en
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