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Molecular study of the surface freez...

Prasad, Shishir.

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Molecular study of the surface freezing phenomenon in materials containing long alkyl chains.

Record Type:	Language materials, printed : Monograph/item
Title/Author:	Molecular study of the surface freezing phenomenon in materials containing long alkyl chains./
Author:	Prasad, Shishir.
Description:	232 p.
Notes:	Adviser: Ali Dhinojwala.
Contained By:	Dissertation Abstracts International68-12B.
Subject:	Chemistry, Physical. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3292806
ISBN:	9780549363019

Molecular study of the surface freezing phenomenon in materials containing long alkyl chains.
Prasad, Shishir.

Molecular study of the surface freezing phenomenon in materials containing long alkyl chains. - 232 p.

Adviser: Ali Dhinojwala.

Thesis (Ph.D.)--The University of Akron, 2007.

Surfaces of most liquids in contact with air have higher entropy and lower melting temperature than the corresponding bulk liquids. Exceptions include materials consisting of linear chains such as n-alkanes, alkane analogues, and poly(n-alkyl acrylate)s, for which the surfaces remain frozen above the bulk melting temperature. We have studied the profound effect of this surface freezing on the static and the dynamic properties of these materials. Along with being a unique 2D effect, the surface frozen monolayer is a perfect example of the quasi 2D-crystal. Hence, it provides an opportunity to study the mechanical properties of 2D solids. Surface sensitive tools such as infrared-visible sum frequency generation spectroscopy, Wilhelmy balance, oscillating bubble surface rheometer, and X-ray synchrotron scattering were used in our investigation.

ISBN: 9780549363019Subjects--Topical Terms:

560527
Chemistry, Physical.

Molecular study of the surface freezing phenomenon in materials containing long alkyl chains.
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008 110630s2007 ||||||||||||||||| ||eng d
020 $a 9780549363019
035 $a (UMI)AAI3292806
035 $a AAI3292806
040 $a UMI $c UMI
100 1 $a Prasad, Shishir. $3 1280769
245 1 0 $a Molecular study of the surface freezing phenomenon in materials containing long alkyl chains.
300 $a 232 p.
500 $a Adviser: Ali Dhinojwala.
500 $a Source: Dissertation Abstracts International, Volume: 68-12, Section: B, page: 8052.
502 $a Thesis (Ph.D.)--The University of Akron, 2007.
520 $a Surfaces of most liquids in contact with air have higher entropy and lower melting temperature than the corresponding bulk liquids. Exceptions include materials consisting of linear chains such as n-alkanes, alkane analogues, and poly(n-alkyl acrylate)s, for which the surfaces remain frozen above the bulk melting temperature. We have studied the profound effect of this surface freezing on the static and the dynamic properties of these materials. Along with being a unique 2D effect, the surface frozen monolayer is a perfect example of the quasi 2D-crystal. Hence, it provides an opportunity to study the mechanical properties of 2D solids. Surface sensitive tools such as infrared-visible sum frequency generation spectroscopy, Wilhelmy balance, oscillating bubble surface rheometer, and X-ray synchrotron scattering were used in our investigation.
520 $a The difference between the surface melting and the bulk melting temperatures is much higher for the poly(n-alkyl acrylate)s compared to their small molecule counterpart, n-alkanes. We have attributed this difference to the partial crystallinity of the alkyl side chains at the surface and the additional length of the surface frozen layer due to the ester linkage in the case of polymers.
520 $a Surface freezing leads to a large surface rearrangement in binary blends of poly(n-alkyl acrylate)s differing only in a couple of methylene side chain units. Only 2 wt.% of the longer side chain component is enough to cover the surfaces below the surface freezing temperature. In addition, the surface transition temperature for the longer side chain component depends weakly on the bulk composition. A comparison of our experimental data with a newly developed thermodynamic model suggests that almost all the side chains of a surface molecule are present in the surface layer upon ordering.
520 $a The surface transition has significant effects on the dynamic properties of these materials. The wetting dynamics of the poly(n-alkyl acrylate)s are dramatically modified by the surface frozen monolayer. The relaxation process of the polymer meniscus in contact with a thin platinum wire slows down by orders of magnitude upon formation of the &sim; 3 nm thick surface ordered layer. Based on our X-ray photon correlation spectroscopy measurements, we have attributed this slowing down to a precursor film.
520 $a The mechanical properties of the surface frozen monolayer were studied by expanding and contracting an air bubble in an n-alkane melt. The surface frozen monolayer crystal ruptures at the grain boundaries. The strength of this 2D crystal depends on the rate of crystal rupture. The interfacial area formed after rupture decreases with a decrease in the rate of bubble oscillation. Interestingly, the broken crystal recovers on a subsecond time scale.
590 $a School code: 0003.
650 4 $a Chemistry, Physical. $3 560527
650 4 $a Chemistry, Polymer. $3 1018428
650 4 $a Engineering, Chemical. $3 1018531
690 $a 0494
690 $a 0495
690 $a 0542
710 2 $a The University of Akron. $3 1018399
773 0 $t Dissertation Abstracts International $g 68-12B.
790 $a 0003
790 1 0 $a Dhinojwala, Ali, $e advisor
791 $a Ph.D.
792 $a 2007
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3292806