SURFACE AND INTERFACE STRUCTURE OF DIBLOCK COPOLYMER BRUSHES

Bibliographic Details
Main Author:	Akgun, Bulent
Language:	English
Published:	University of Akron / OhioLINK 2007
Subjects:	Polymer brushes diblock copolymer brushes surface fluctuations stimuli-responsive thin polymer films interface structure of thin films.
Online Access:	http://rave.ohiolink.edu/etdc/view?acc_num=akron1169048648

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spelling	ndltd-OhioLink-oai-etd.ohiolink.edu-akron11690486482021-08-03T05:24:59Z SURFACE AND INTERFACE STRUCTURE OF DIBLOCK COPOLYMER BRUSHES Akgun, Bulent Polymer brushes diblock copolymer brushes surface fluctuations stimuli-responsive thin polymer films interface structure of thin films. The main objective of the work presented in this thesis is to understand the surface and interface structure and dynamics of diblock copolymer brushes (DCBs). DCBs are stimuli-responsive materials and the surface properties of a DCB can be changed from those characteristic of one polymer block to those characteristic of the other one by treating the DCB with a solvent selective for one of its blocks. For this purpose, polystyrene-block-polyacrylate or polyacrylate-block-polystyrene brushes were synthesized using the “grafting from” technique in combination with atom transfer radical polymerization (ATRP). In the first part of this project the internal structure of DCBs after the synthesis and surface rearrangement were investigated using neutron reflectivity (NR) and grazing incidence small angle X-ray scattering (GISAXS). It was found that the internal brush structure depends strongly on the synthesis sequence of polymer blocks and the value of xN. For small values of xN (xN is smaller than 11), a model of two layers with an interfacial region of finite width provides a good description of the data. The interface width is found to be larger for DCBs which have the polymer block with the lower surface energy synthesized next to the substrate. A three layer model must be used to describe the structure of DCBs of larger xN values (xN is greater than 23) and of sufficiently asymmetric composition. The necessity of including a third layer is consistent with the presence of a lateral ordering of some type in the center of the brush, as evidenced by correlation peaks in the GISAXS data. The spacing of the in-plane ordering varies with the thickness of the poly(methyl acrylate) (PMA) block. After a DCB is treated with a selective solvent, Bragg rods appear in the GISAXS pattern. The appearance of Bragg rods indicates the formation of a new 2D structure which has a lateral spacing on the order of the total thickness of the brush. The Bragg rods disappear upon heating to 80 degree celcius. Roughness correlation between the interfaces of a DCB has been detected using longitudinal diffuse X-ray scattering and X-ray reflectivity. The amplitude of the fringes in the longitudinal diffuse scattering decreases with increasing thickness of the DCB, indicating that the interactions between substrate and brush surface decrease as the thickness of the DCB increases. Roughness correlation of the brush is observed after annealing the brush but, it is lost after the brush is swollen in the vapor of a nonselective solvent, dichloromethane. A remarkable suppression of polymer film surface fluctuations by the tethering of one end of each chain in a densely grafted brush has been demonstrated experimentally using X-ray Photon Correlation Spectroscopy (XPCS), a direct measure of dynamics. Within the range of time and length scale investigated, 0.2 s to 1100 s, and 200 nm to 5 um, no relaxation of the brush surface could be observed, even 170 degree celcius above the bulk glass transition temperature of corresponding untethered chains, suggesting that the surface relaxation time is increased by at least three orders of magnitude as compared to a film of untethered chains of comparable thickness. The observation of the suppression of long wavelength fluctuations on the surface of a dry homopolymer brush is consistent with theoretical predictions. 2007-10-02 English text University of Akron / OhioLINK http://rave.ohiolink.edu/etdc/view?acc_num=akron1169048648 http://rave.ohiolink.edu/etdc/view?acc_num=akron1169048648 unrestricted This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws.
collection	NDLTD
language	English
sources	NDLTD
topic	Polymer brushes diblock copolymer brushes surface fluctuations stimuli-responsive thin polymer films interface structure of thin films.
spellingShingle	Polymer brushes diblock copolymer brushes surface fluctuations stimuli-responsive thin polymer films interface structure of thin films. Akgun, Bulent SURFACE AND INTERFACE STRUCTURE OF DIBLOCK COPOLYMER BRUSHES
author	Akgun, Bulent
author_facet	Akgun, Bulent
author_sort	Akgun, Bulent
title	SURFACE AND INTERFACE STRUCTURE OF DIBLOCK COPOLYMER BRUSHES
title_short	SURFACE AND INTERFACE STRUCTURE OF DIBLOCK COPOLYMER BRUSHES
title_full	SURFACE AND INTERFACE STRUCTURE OF DIBLOCK COPOLYMER BRUSHES
title_fullStr	SURFACE AND INTERFACE STRUCTURE OF DIBLOCK COPOLYMER BRUSHES
title_full_unstemmed	SURFACE AND INTERFACE STRUCTURE OF DIBLOCK COPOLYMER BRUSHES
title_sort	surface and interface structure of diblock copolymer brushes
publisher	University of Akron / OhioLINK
publishDate	2007
url	http://rave.ohiolink.edu/etdc/view?acc_num=akron1169048648
work_keys_str_mv	AT akgunbulent surfaceandinterfacestructureofdiblockcopolymerbrushes
_version_	1719419588220813312

SURFACE AND INTERFACE STRUCTURE OF DIBLOCK COPOLYMER BRUSHES

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