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Microstructure and phase behavior in...

Lohr, Matthew Alan.

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Microstructure and phase behavior in colloids and liquid crystals.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Microstructure and phase behavior in colloids and liquid crystals./
作者:	Lohr, Matthew Alan.
面頁冊數:	221 p.
附註:	Source: Dissertation Abstracts International, Volume: 76-01(E), Section: B.
Contained By:	Dissertation Abstracts International76-01B(E).
標題:	Condensed matter physics. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3634030
ISBN:	9781321142266

Microstructure and phase behavior in colloids and liquid crystals.
Lohr, Matthew Alan.

Microstructure and phase behavior in colloids and liquid crystals. - 221 p.

Source: Dissertation Abstracts International, Volume: 76-01(E), Section: B.

Thesis (Ph.D.)--University of Pennsylvania, 2014.

This item must not be sold to any third party vendors.

This thesis describes our investigation of microstructure and phase behavior in colloids and liquid crystals. The first set of experiments explores the phase behavior of helical packings of thermoresponsive microspheres inside glass capillaries as a function of volume fraction. Stable helical packings are observed with long-range orientational order. Some of these packings evolve abruptly to disordered states as the volume fraction is reduced. We quantify these transitions using correlation functions and susceptibilities of an orientational order parameter. The emergence of coexisting metastable packings, as well as coexisting ordered and disordered states, is also observed. These findings support the notion of phase-transition-like behavior in quasi-one-dimensional systems.

ISBN: 9781321142266Subjects--Topical Terms:

3173567
Condensed matter physics.

Microstructure and phase behavior in colloids and liquid crystals.
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100 1 $a Lohr, Matthew Alan. $3 3173566
245 1 0 $a Microstructure and phase behavior in colloids and liquid crystals.
300 $a 221 p.
500 $a Source: Dissertation Abstracts International, Volume: 76-01(E), Section: B.
500 $a Adviser: Arjun G. Yodh.
502 $a Thesis (Ph.D.)--University of Pennsylvania, 2014.
506 $a This item must not be sold to any third party vendors.
520 $a This thesis describes our investigation of microstructure and phase behavior in colloids and liquid crystals. The first set of experiments explores the phase behavior of helical packings of thermoresponsive microspheres inside glass capillaries as a function of volume fraction. Stable helical packings are observed with long-range orientational order. Some of these packings evolve abruptly to disordered states as the volume fraction is reduced. We quantify these transitions using correlation functions and susceptibilities of an orientational order parameter. The emergence of coexisting metastable packings, as well as coexisting ordered and disordered states, is also observed. These findings support the notion of phase-transition-like behavior in quasi-one-dimensional systems.
520 $a The second set of experiments investigates cross-over behavior from glasses with attractive interactions to sparse gel-like states. In particular, the vibrational modes of quasi-two-dimensional disordered colloidal packings of hard colloidal spheres with short-range attractions are measured as a function of packing fraction. A crossover from glassy to sparse gel-like states is indicated by an excess of low-frequency phonon modes. This change in vibrational mode distribution appears to arise from highly localized vibrations that tend to involve individual and/or small clusters of particles with few local bonds. These mode behaviors and corresponding structural insights may serve as a useful signature for glass-gel transitions in wider classes of attractive packings.
520 $a A third set of experiments explores the director structures of aqueous lyotropic chromonic liquid crystal (LCLC) films created on square lattice cylindrical-micropost substrates. The structures are manipulated by modulating of the concentration-dependent elastic properties of LCLC s via drying. Nematic LCLC films exhibit preferred bistable alignment along the diagonals of the micropost lattice. Columnar LCLC films form two distinct director and defect configurations: a diagonally aligned director pattern with local squares of defects, and an off-diagonal configuration with zig-zag defects. The formation of these patterns appears to be tied to the relative free energy costs of splay and bend deformations in the precursor nematic films. The observed nematic and columnar configurations are understood numerically using a Landau-de Gennes free energy model. This work provides first examples of quasi-2D micropatterning of LC films in the columnar phase and the first micropatterning of lyotropic LC films in general, as well as demonstrating alignment and configuration switching of typically difficult-to-align LCLC films via bulk elastic properties.
590 $a School code: 0175.
650 4 $a Condensed matter physics. $3 3173567
650 4 $a Chemical engineering. $3 560457
690 $a 0611
690 $a 0542
710 2 $a University of Pennsylvania. $b Physics and Astronomy. $3 2101621
773 0 $t Dissertation Abstracts International $g 76-01B(E).
790 $a 0175
791 $a Ph.D.
792 $a 2014
793 $a English
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3634030