Journal Article

PreJuSER-20017

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Dynamics of 1,3-diphenylpropane tethered to the interior pore surfaces of MCM-41

Kintzel, E. J. ; Kidder, M. K. ; Buchanan, A. C. ; Britt, P. F. ; Mamontov, E. ; Zamponi, M.FZJ* ; Herwig, K. W.

2012
Soc. Washington, DC

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Please use a persistent id in citations: doi:10.1021/jp209458a

Abstract: The diffusive motions of covalently tethered 1,3-diphenylpropane (DPP) via a silyl-aryl-ether linkage in the mesopores of MCM-41 were studied by quasielastic neutron scattering. The geometric effect of pore radius was investigated with samples having pores that ranged from 1.6 to 3.0 nm in diameter and highest achievable DPP grafting density. The effect of molecular crowding was investigated in 3.0 rim diameter pores for surface coverage ranging from 0.60 to 1.61 DPP/nm(2). Temperature dependence was determined for large pore diameter samples from 240 to 370 K. As the DPP molecules remain attached over this entire temperature range, data were analyzed in terms of a model of localized diffusion inside a sphere. Only the motions of the DPP hydrogen atoms were considered because of the high sensitivity of neutron scattering to the presence of hydrogen. As atoms far from the attachment point have a greater range of motion than those nearer the tether, the radius of the sphere limiting the motion of individual hydrogen atoms was allowed to increase based on the atom's distance from the tether point Both smaller pore diameters and higher DPP grafting density resulted in larger amplitude motion while the diffusion coefficient was greatest in the largest pores at highest DPP density. These observations support a model where the DPP molecules prefer an orientation allowing close proximity to the MCM-41 pore surface and are forced into the pore interior by either the steric effect of small pore diameter or by increased competition for surface area at high molecule surface coverage.

Keyword(s): Basic research (1st) ; Others (1st) ; Condensed Matter Physics (2nd) ; J

Note: A portion of this research was performed at Oak Ridge National Laboratory's Spallation Neutron Source which is sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy. M.K.K, P.F.B., and A.C.B.III, acknowledge the support of the Division of Chemical Sciences, Geosciences, and Biosciences, Office of Basic Energy Sciences, U.S. Department of Energy. We also acknowledge the support of the National Institute of Standards and Technology, U.S. Department of Commerce, in providing some of the neutron research facilities used in this work. This work utilized facilities supported in part by the National Science Foundation under Agreement No. DMR-094477. We would like to acknowledge the assistance of A.T. Ruffin in early data analysis and would like to thank A. L. Chaffee for fruitful discussions and the kind use of the images used in Figure 4.

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Contributing Institute(s):

1. Neutronenstreuung (ICS-1)
2. JCNS-FRM-II (JCNS (München) ; Jülich Centre for Neutron Science JCNS (München) ; JCNS-FRM-II)
3. Neutronenstreuung (JCNS-1)

Research Program(s):

1. BioSoft: Makromolekulare Systeme und biologische Informationsverarbeitung (P45)
2. Großgeräte für die Forschung mit Photonen, Neutronen und Ionen (PNI) (P55)

Experiment(s):

1. External Measurement

Appears in the scientific report 2012

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Database coverage:
; Current Contents - Social and Behavioral Sciences ; JCR ; SCOPUS ; Science Citation Index ; Science Citation Index Expanded ; Thomson Reuters Master Journal List ; Web of Science Core Collection

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