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Phase Behavior Study and Thermoresponsive Bilayer Fabrication of Organogels /

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Phase Behavior Study and Thermoresponsive Bilayer Fabrication of Organogels // Tzu-Yu Lai.
作者:	Lai, Tzu-Yu,
面頁冊數:	1 electronic resource (211 pages)
附註:	Source: Dissertations Abstracts International, Volume: 84-12, Section: B.
Contained By:	Dissertations Abstracts International84-12B.
標題:	Materials science. -
電子資源:	https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=30557127
ISBN:	9798379604998

Phase Behavior Study and Thermoresponsive Bilayer Fabrication of Organogels /
Lai, Tzu-Yu,

Phase Behavior Study and Thermoresponsive Bilayer Fabrication of Organogels /Tzu-Yu Lai. - 1 electronic resource (211 pages)

Source: Dissertations Abstracts International, Volume: 84-12, Section: B.

Organogels are classified as a type of semisolid gels with an organic phase immobilized inside a three-dimensional, physically or chemically crosslinked network. The growth of this field, especially for applications in medicine and biotechnology, is rapid. The designability of organogels provides a wide range of applications by tailoring the selected gelators and solvents. The work summarized in this abstract will focus on two approaches on studies of organogels - (1) theoretical understanding on the thermodynamic phase behavior of low molecular organotgelators in systematic non-polar solvents and (2) expanding application uses on the fabrication of thermally sensitive actuators formed by elastomer organogels.The first project is a study of the phase behavior of a low molecular organotgelators, R-12-hydroxystearic acid (12-HSA), which is widely known to act as an excellent molecular gelator for a range of organic solvents. Researchers have tried to understand the mechanism contributing to this good gelation ability primarily from the viewpoint of the self-assembled crystalline morphology and the solution interaction based on the solubility parameter between solvent and gelator. However, the role of gelator aggregation in the pre-gel (i.e. liquid) state has not been widely explored, especially its influence on the macroscopic gelation behavior. In this fundamental focus, full phase diagrams of 12-HSA in n-alkanes (which have small variation in solubility parameter but large variation in molecular size) were presented to emphasize the role of gelator aggregation and its entropic contribution to gelation system. Qualitative trends in the uplift of liquidus line and the appearance of asymmetric miscibility gap with increasing molecular size of n-alkanes were observed. Overall, the 12-HSA/n-alkane system demonstrates the importance of liquid state assembly and aggregation as an untapped and important parameter in tailoring good molecular gelators.Continuing the concept of the importance in gelator aggregation form the first project, a novel type of gelator composed of dicarboxylic acids which have high melting temperature (> 100 °C) but are poorly soluble in non-polar solvents is proposed. Monocarboxylic acids were introduced as end-cappers to cap the laterally linking dicarboxylic acids via hydrogen bonds and increase the solubility by reducing the degree of supramolecular aggregation. The small amount of monocarboxylic acids (4 mol%) has been proved to assist dicarboxylic acids dissolve and gel the non-polar solvent; however, a large temperature gap between gelation temperature and cloud point of diacid/monoacid mixtures was noticed. Ternary phase diagrams of diacid/monoacid mixtures were mapped out and the poor gelation performance was explained.To fulfill the second approach, polystyrene-block-polyethylene-r-polybutylene-block-polystyrene (SEBS) is used as a polymer matrix containing up to 75 mass % (relative to the matrix) wax, known as phase-change materials with large volumetric expansion of 30% on melting, in the ethylene-butylene-rich domains. Commercially available polyimide film is utilized as the passive layer. By exploiting the motion (bending or curling) created by a mismatch of volumetric expansion between two laminated layers, the wax-loaded active layer formed by the elastomer organogels successfully shows promising performance for reproducible, traceable and cyclic actuation.In addition, the compression of microdomain spacing of pure SEBS film, due to solvent evaporation at the film thickness direction, was discovered. Systematic studies by small angle X-ray scattering measurements were conducted. The creation of these nonequilibrium structures accounts for the rapid chain mobility loss at the casting temperature far from the glass transition temperature of styrene domain. By taking advantage of regaining the chain mobility to achieve thermodynamically stable structures, the degree of recovery from the compressed domain under elevated temperature can be controlled. SEBS film has firmly pined on the passive layer (polyimide films), so that recovery of the compressed domain was strongly linked on the performance of bending behaviors. Eventually, the adjustable sequential bending of SEBS bilayers was performed.

English

ISBN: 9798379604998Subjects--Topical Terms:

543314
Materials science.
Subjects--Index Terms:

Organogel

Phase Behavior Study and Thermoresponsive Bilayer Fabrication of Organogels /
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500 $a Source: Dissertations Abstracts International, Volume: 84-12, Section: B.
500 $a Advisors: Cavicchi, Kevin A. Committee members: Kyu, Thein; Miyoshi, Toshikazu; Xu, Weinan; Zheng, Jie.
502 $b Ph.D. $c The University of Akron $d 2020.
520 $a Organogels are classified as a type of semisolid gels with an organic phase immobilized inside a three-dimensional, physically or chemically crosslinked network. The growth of this field, especially for applications in medicine and biotechnology, is rapid. The designability of organogels provides a wide range of applications by tailoring the selected gelators and solvents. The work summarized in this abstract will focus on two approaches on studies of organogels - (1) theoretical understanding on the thermodynamic phase behavior of low molecular organotgelators in systematic non-polar solvents and (2) expanding application uses on the fabrication of thermally sensitive actuators formed by elastomer organogels.The first project is a study of the phase behavior of a low molecular organotgelators, R-12-hydroxystearic acid (12-HSA), which is widely known to act as an excellent molecular gelator for a range of organic solvents. Researchers have tried to understand the mechanism contributing to this good gelation ability primarily from the viewpoint of the self-assembled crystalline morphology and the solution interaction based on the solubility parameter between solvent and gelator. However, the role of gelator aggregation in the pre-gel (i.e. liquid) state has not been widely explored, especially its influence on the macroscopic gelation behavior. In this fundamental focus, full phase diagrams of 12-HSA in n-alkanes (which have small variation in solubility parameter but large variation in molecular size) were presented to emphasize the role of gelator aggregation and its entropic contribution to gelation system. Qualitative trends in the uplift of liquidus line and the appearance of asymmetric miscibility gap with increasing molecular size of n-alkanes were observed. Overall, the 12-HSA/n-alkane system demonstrates the importance of liquid state assembly and aggregation as an untapped and important parameter in tailoring good molecular gelators.Continuing the concept of the importance in gelator aggregation form the first project, a novel type of gelator composed of dicarboxylic acids which have high melting temperature (> 100 °C) but are poorly soluble in non-polar solvents is proposed. Monocarboxylic acids were introduced as end-cappers to cap the laterally linking dicarboxylic acids via hydrogen bonds and increase the solubility by reducing the degree of supramolecular aggregation. The small amount of monocarboxylic acids (4 mol%) has been proved to assist dicarboxylic acids dissolve and gel the non-polar solvent; however, a large temperature gap between gelation temperature and cloud point of diacid/monoacid mixtures was noticed. Ternary phase diagrams of diacid/monoacid mixtures were mapped out and the poor gelation performance was explained.To fulfill the second approach, polystyrene-block-polyethylene-r-polybutylene-block-polystyrene (SEBS) is used as a polymer matrix containing up to 75 mass % (relative to the matrix) wax, known as phase-change materials with large volumetric expansion of 30% on melting, in the ethylene-butylene-rich domains. Commercially available polyimide film is utilized as the passive layer. By exploiting the motion (bending or curling) created by a mismatch of volumetric expansion between two laminated layers, the wax-loaded active layer formed by the elastomer organogels successfully shows promising performance for reproducible, traceable and cyclic actuation.In addition, the compression of microdomain spacing of pure SEBS film, due to solvent evaporation at the film thickness direction, was discovered. Systematic studies by small angle X-ray scattering measurements were conducted. The creation of these nonequilibrium structures accounts for the rapid chain mobility loss at the casting temperature far from the glass transition temperature of styrene domain. By taking advantage of regaining the chain mobility to achieve thermodynamically stable structures, the degree of recovery from the compressed domain under elevated temperature can be controlled. SEBS film has firmly pined on the passive layer (polyimide films), so that recovery of the compressed domain was strongly linked on the performance of bending behaviors. Eventually, the adjustable sequential bending of SEBS bilayers was performed.
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590 $a School code: 0003
650 4 $a Materials science. $3 543314
650 4 $a Polymer chemistry. $3 3173488
650 4 $a Organic chemistry. $3 523952
653 $a Organogel
653 $a Molecular organogelators
653 $a Phase diagram
653 $a Block copolymer
653 $a Alkanes
690 $a 0794
690 $a 0490
690 $a 0495
710 2 $a The University of Akron. $b Polymer Engineering. $e degree granting institution. $3 3823983
720 1 $a Cavicchi, Kevin A. $e degree supervisor.
773 0 $t Dissertations Abstracts International $g 84-12B.
790 $a 0003
791 $a Ph.D.
792 $a 2020
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