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The effect of nanoconfinement on the...

Mundra, Manish Kumar.

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The effect of nanoconfinement on the glass transition temperature (Tg) and mobility associated with diffusion in polymer films: A fluorescence study.

Record Type:	Language materials, printed : Monograph/item
Title/Author:	The effect of nanoconfinement on the glass transition temperature (Tg) and mobility associated with diffusion in polymer films: A fluorescence study./
Author:	Mundra, Manish Kumar.
Description:	357 p.
Notes:	Adviser: John M. Torkelson.
Contained By:	Dissertation Abstracts International68-09B.
Subject:	Chemistry, Polymer. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3278067
ISBN:	9780549220503

The effect of nanoconfinement on the glass transition temperature (Tg) and mobility associated with diffusion in polymer films: A fluorescence study.
Mundra, Manish Kumar.

The effect of nanoconfinement on the glass transition temperature (Tg) and mobility associated with diffusion in polymer films: A fluorescence study. - 357 p.

Adviser: John M. Torkelson.

Thesis (Ph.D.)--Northwestern University, 2007.

In this dissertation, the Tg behavior of nanoconfined polymer films and 1-dimensional (1-D) patterned polymer nanostructures was studied. Using a novel fluorescence method, a reduction in Tg was observed upon confinement in PS films supported on silica, where free-surface (polymer-air interface) effects are dominant in modifying Tg. In contrast, Tg was observed to increase upon nanoconfinement in poly(methyl methacrylate) (PMMA) films supported on silica, where moderate attractive polymer-substrate interactions are present. By placing dye-labeled polymer films in a multilayer geometry with unlabeled polymer films, unique information was obtained on the effect of interfaces in modifying Tg upon confinement and the distribution of Tgs across the multilayer film thickness. In particular, with nanoscale confinement of PMMA films it was shown how the free-surface effect competes with and is overwhelmed by the substrate effect. In a first ever measurement, it was demonstrated that this competition leads to a free-surface layer Tg exceeding the bulk polymer Tg. This research also led to the first study of Tg-nanoconfinement effects in 1-D polymer nanostructures. As with films, interfacial interactions dictate the ultimate Tg behavior of nanostructures.

ISBN: 9780549220503Subjects--Topical Terms:

1018428
Chemistry, Polymer.

The effect of nanoconfinement on the glass transition temperature (Tg) and mobility associated with diffusion in polymer films: A fluorescence study.
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005 20110523
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020 $a 9780549220503
035 $a (UMI)AAI3278067
035 $a AAI3278067
040 $a UMI $c UMI
100 1 $a Mundra, Manish Kumar. $3 1269517
245 1 4 $a The effect of nanoconfinement on the glass transition temperature (Tg) and mobility associated with diffusion in polymer films: A fluorescence study.
300 $a 357 p.
500 $a Adviser: John M. Torkelson.
500 $a Source: Dissertation Abstracts International, Volume: 68-09, Section: B, page: 6234.
502 $a Thesis (Ph.D.)--Northwestern University, 2007.
520 $a In this dissertation, the Tg behavior of nanoconfined polymer films and 1-dimensional (1-D) patterned polymer nanostructures was studied. Using a novel fluorescence method, a reduction in Tg was observed upon confinement in PS films supported on silica, where free-surface (polymer-air interface) effects are dominant in modifying Tg. In contrast, Tg was observed to increase upon nanoconfinement in poly(methyl methacrylate) (PMMA) films supported on silica, where moderate attractive polymer-substrate interactions are present. By placing dye-labeled polymer films in a multilayer geometry with unlabeled polymer films, unique information was obtained on the effect of interfaces in modifying Tg upon confinement and the distribution of Tgs across the multilayer film thickness. In particular, with nanoscale confinement of PMMA films it was shown how the free-surface effect competes with and is overwhelmed by the substrate effect. In a first ever measurement, it was demonstrated that this competition leads to a free-surface layer Tg exceeding the bulk polymer Tg. This research also led to the first study of Tg-nanoconfinement effects in 1-D polymer nanostructures. As with films, interfacial interactions dictate the ultimate Tg behavior of nanostructures.
520 $a This research has contributed in other ways to understanding the effects of nanoscale confinement on polymer properties. Using small variations in the repeat unit structure and backbone rigidity or addition of low molecular weight diluents, it was demonstrated that the magnitude of the Tg -nanoconfinement effect is strongly tunable in polymers and can result in deviations from bulk Tg of about 45-50 K. Furthermore, this tunability can be understood qualitatively based on fundamental polymer physics related to cooperative segmental mobility.
520 $a In this dissertation a new method was also developed based on simple fluorescence to determine the effect of confinement on the diffusion coefficients of small dye molecules and found that diffusion coefficients can differ by as much as an order of magnitude in 125-nm-thick films as compared with bulk films. Finally, a novel technique that uses intrinsic fluorescence to characterize the effect of confinement on Tg in thin and ultrathin films of styrene containing copolymers as well as the effect of stress relaxation on local chain conformations was also developed.
590 $a School code: 0163.
650 4 $a Chemistry, Polymer. $3 1018428
650 4 $a Engineering, Materials Science. $3 1017759
690 $a 0495
690 $a 0794
710 2 $a Northwestern University. $b Materials Science and Engineering. $3 1058406
773 0 $t Dissertation Abstracts International $g 68-09B.
790 $a 0163
790 1 0 $a Broadbelt, Linda J. $e committee member
790 1 0 $a Dravid, Vinayak P. $e committee member
790 1 0 $a Shull, Kenneth R. $e committee member
790 1 0 $a Torkelson, John M., $e advisor
791 $a Ph.D.
792 $a 2007
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3278067