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Control, manipulation, characterizat...

Wu, Wei.

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Control, manipulation, characterization and complex crystallization behavior of macromolecular assemblies.

Record Type:	Language materials, printed : Monograph/item
Title/Author:	Control, manipulation, characterization and complex crystallization behavior of macromolecular assemblies./
Author:	Wu, Wei.
Description:	213 p.
Notes:	Source: Dissertation Abstracts International, Volume: 69-01, Section: B, page: 0348.
Contained By:	Dissertation Abstracts International69-01B.
Subject:	Chemistry, Polymer. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3299656
ISBN:	9780549437536

Control, manipulation, characterization and complex crystallization behavior of macromolecular assemblies.
Wu, Wei.

Control, manipulation, characterization and complex crystallization behavior of macromolecular assemblies. - 213 p.

Source: Dissertation Abstracts International, Volume: 69-01, Section: B, page: 0348.

Thesis (Ph.D.)--Carnegie Mellon University, 2008.

This thesis focused on the discussion on three major aspects of polymeric materials development synthesis, manipulation, characterization, as well as on complex crystallization behavior of macromolecular assemblies. The studies started with the controlled synthesis of ABA type triblock copolymers containing side chain crystalline segments poly(octadecyl methacrylate) (PODMA) and poly(docosyl methacrylate) (PDSMA) via ATRP, followed by the characterization of these materials at various scales. Small angle X ray scattering (SAXS) provided the reciprocal space information about the copolymer nanostruetures averaged over macroscopic sampling volumes, whereas atomic force microscopy (AFM) revealed the real space nanoseale topography of the material surtnces, often with nearly molecular resolution, e.g., with molecular resolution of poly(nBA) chains from single wailed carbon nanotubes. This structural characterization was complemented by differential scanning calorimetry (DSC) which provided information about the thermal transitions such as crystallization/melting and vitritication/devitrilication. The demonstrated capability or tapping mode to spatially resolve the thermal transitions through mechanical mapping of the surface, points to a new way to study materials at nanometer scale. The characterization tools and strategies described in this thesis, provide unprecedented insights in the characterization of block copolymers using tapping mode AFM, and lead to the emergence of new proximal probe techniques. The macromolecular conformation of block copolymers with main chain crystallinity, i.e., poly(ethylene) (PEO) and poly(caprolactone) (PCL), was found to be also significantly related to the morphologies of the block copolymers. The crystalline block formed the continuous phase in block copolymers when it is partially miscible with the amorphous block or when the amorphous block is relatively short. The crystalline block crystallized into lamellae through chain folding followed by the rejection of flanking amorphous polymer chains from the lamellae. In such cases, the crystallization was found to be controlled by heterogeneous nucleation, similar to the one in homopolymer. In contrast, the crystalline block dispersed in the amorphous matrix, represented an example of homogeneous nucleation and fractionated crystallization, due to the significant suppression of nucleation. For block copolymers with more than one crystalline block, e.g., in the case of PCL-PnBA-PODMA, the length of the linkage between the main and side chain crystalline block was also found to affect the crystallization behavior of the two crystalline blocks, i.e., PCL and PODMA could crystallize coincidentally with a short PnBA linkage. The presence of boundaries/interfaces imposed by the microphase separation gave rise to the differences in the way how polymer chains would be oriented at the boundaries, which is the origin of the different crystallinities found in different morphologies. Understanding of the investigated partially crystalline block copolymer systems shed lights on the strategies to manipulating the macromolecular assemblies of block copolymers at various size scales. Zone casting represents the new strategy to achieve the long range ordered assemblies of block copolymer domains without the need of any external fields. In certain way, this technique is similar to another approach, applicable to the polymers solidifying from the melt rather than from solution, and relying on the imposition of boundary conditions and temperature gradient. Interestingly, the same perpendicular ordering of block copolymer lamellae with respect to the solidification direction was observed in both strategies, pointing to rote of interfacial energies under similar boundary conditions. Another type of manipulation of block copolymer assemblies is the supramolecular ordering of amphiphilic block copolymers in aqueous solution. Biomimetic constructs based on this design principle could in the future find applications as biocompatible carriers for drug delivery.

ISBN: 9780549437536Subjects--Topical Terms:

1018428
Chemistry, Polymer.

Control, manipulation, characterization and complex crystallization behavior of macromolecular assemblies.
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500 $a Source: Dissertation Abstracts International, Volume: 69-01, Section: B, page: 0348.
502 $a Thesis (Ph.D.)--Carnegie Mellon University, 2008.
520 $a This thesis focused on the discussion on three major aspects of polymeric materials development synthesis, manipulation, characterization, as well as on complex crystallization behavior of macromolecular assemblies. The studies started with the controlled synthesis of ABA type triblock copolymers containing side chain crystalline segments poly(octadecyl methacrylate) (PODMA) and poly(docosyl methacrylate) (PDSMA) via ATRP, followed by the characterization of these materials at various scales. Small angle X ray scattering (SAXS) provided the reciprocal space information about the copolymer nanostruetures averaged over macroscopic sampling volumes, whereas atomic force microscopy (AFM) revealed the real space nanoseale topography of the material surtnces, often with nearly molecular resolution, e.g., with molecular resolution of poly(nBA) chains from single wailed carbon nanotubes. This structural characterization was complemented by differential scanning calorimetry (DSC) which provided information about the thermal transitions such as crystallization/melting and vitritication/devitrilication. The demonstrated capability or tapping mode to spatially resolve the thermal transitions through mechanical mapping of the surface, points to a new way to study materials at nanometer scale. The characterization tools and strategies described in this thesis, provide unprecedented insights in the characterization of block copolymers using tapping mode AFM, and lead to the emergence of new proximal probe techniques. The macromolecular conformation of block copolymers with main chain crystallinity, i.e., poly(ethylene) (PEO) and poly(caprolactone) (PCL), was found to be also significantly related to the morphologies of the block copolymers. The crystalline block formed the continuous phase in block copolymers when it is partially miscible with the amorphous block or when the amorphous block is relatively short. The crystalline block crystallized into lamellae through chain folding followed by the rejection of flanking amorphous polymer chains from the lamellae. In such cases, the crystallization was found to be controlled by heterogeneous nucleation, similar to the one in homopolymer. In contrast, the crystalline block dispersed in the amorphous matrix, represented an example of homogeneous nucleation and fractionated crystallization, due to the significant suppression of nucleation. For block copolymers with more than one crystalline block, e.g., in the case of PCL-PnBA-PODMA, the length of the linkage between the main and side chain crystalline block was also found to affect the crystallization behavior of the two crystalline blocks, i.e., PCL and PODMA could crystallize coincidentally with a short PnBA linkage. The presence of boundaries/interfaces imposed by the microphase separation gave rise to the differences in the way how polymer chains would be oriented at the boundaries, which is the origin of the different crystallinities found in different morphologies. Understanding of the investigated partially crystalline block copolymer systems shed lights on the strategies to manipulating the macromolecular assemblies of block copolymers at various size scales. Zone casting represents the new strategy to achieve the long range ordered assemblies of block copolymer domains without the need of any external fields. In certain way, this technique is similar to another approach, applicable to the polymers solidifying from the melt rather than from solution, and relying on the imposition of boundary conditions and temperature gradient. Interestingly, the same perpendicular ordering of block copolymer lamellae with respect to the solidification direction was observed in both strategies, pointing to rote of interfacial energies under similar boundary conditions. Another type of manipulation of block copolymer assemblies is the supramolecular ordering of amphiphilic block copolymers in aqueous solution. Biomimetic constructs based on this design principle could in the future find applications as biocompatible carriers for drug delivery.
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