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Well-Defined Periodic Minimal Surface of Block Copolymer Bilayers

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Title
Well-Defined Periodic Minimal Surface of Block Copolymer Bilayers
Author
An, Tae Hyun
Advisor
Kim, Kyoung Taek
Keywords
Amphiphilic block copolymers; Self-assembly; Cubosomes
Issue Date
2015-02
Publisher
Graduate school of UNIST
Abstract
A tri-arm PEG initiator was synthesized from PEG550, PEG 750 in four steps and block copolymers of tri-arm Poly(ethylene glycol) (PEG) initiator and Poly(styrene) (PS) were synthesized by the Atom Transfer radical polymerization (ATRP)method and Anionic polymerization & cyclo-addition. So The amphiphilic block copolymers, Tri-arm PEG-b-PSx, self-assembled into a variety of nanostructures including spherical and cylindrical micelles, polymer vesicles, inverse cubic mesophase(cubosomes) and inverse hexagonal phase according to degree of polymerization of the PSx block in water. In my study, I will focus on the inverse cubic mesophase(cubosomes). The morphology of the self-assembled structures were observed on transmission electron microscopy (TEM), scanning electron microscopy (SEM) and small angle X-ray scattering(SAXS). Cubosomes of these block copolymers have a high surface area, stronger than lipid cubosomes. When the self-assembly of block copolymer, put 3~15% of end-functionalized linear block copolymer(similar fraction of tri-arm block copolymer). The PEG end of the linear block copolymer have SH, N3 and NH2 which are attach dye, enzyme and DNA. fluorescein isothiocyanate(FITC) and Rhodamine attached cubosome’s surface via SH, N3, NH2. Functionalized cubosomes were confirmed by laser confocal fluorescence microscopy (LCFM). The internal lattice structure of the self-assembled inverse cubic mesophases change via mixing linear block copolymer and The solvent effect. The amounts of linear block copolymer increase the internal lattice structure changing D-minimal surfaces(Pn3m) to Schwartz P-minimal(Im3m) in aqueous solution. Increasing the amounts of N,N-dimethylformamide(DMF) solvent change polymersomes from lamella to D-minimal surfaces(Pn3m) in aqueous solution. The change of internal structure were observed on scanning electron microscopy (SEM) and small angle X-ray scattering(SAXS). Monoliths film is the direct solution self-assembly of BCPs having branched hydrophilic blocks (triarm-linear BCPs) into large monoliths consisting of the triply periodic minimal surface (TPMS) of the BCP bilayer, which was driven by the diffusion of a poor solvent (water) into the BCP solution under controlled humidity. The internal network of the water channels could be used as a platform to accommodate guest molecules such as protein complexes, and the monolith was also demonstrated as a scaffold for the synthesis of 3-D skeletal nanostructures of inorganic oxides with hierarchical porous networks. Based on the experimental results, the inverse cubic mesophase in cubosomes and monolithic film was observed. It showed a high surface area, stronger than lipid cubosomes and long path length that prove promising for enzyme reactor, separation, filteration, desalination, proteocubosome and template of replica.
Description
Department of Chemistry
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