SCMF Analysis for The Amphiphilic Block Copolymer/Solvent System and Its Applications on Nanomaterials
Date Issued
2004
Date
2004
Author(s)
CHANG, YUNG
DOI
en-US
Abstract
Amphiphilic block copolymers have become new approaches for preparing nanomaterials with accessible self-assembled morphologies. However, the precise control on the length scale of microstructure from amphiphilic block copolymers has not been fully explored. In this thesis, self-consistent mean-field (SCMF) was employed to analyze phase and scale behavior of the amphiphilic block copolymer/solvent systems and its applications on pore morphology analysis of nanoporous methyl silsesquioxane.
In the first part of this dissertation, the effects of solvent addition on body- centered cubic (bcc) spheres of block copolymers was investigated by SCMF calculations. For the case of amphiphilic block copolymer/neutral solvent system, the accuracy of the dilution approximation, the scaling behavior of the bcc structural sizes with copolymer volume fraction, the interaction parameter, and degree of copolymerization were analyzed. The study systematically analyzed the effects of neutral solvent accumulation at the interface on the resulting length scales of each segregated domain, such as the A-rich and B-rich phases, as well as the interfacial width for the block copolymer spheres in the bcc array. In particular, it was found that more solvent accumulation at the interfaces resulted in the increase of deviation from the dilution approximation. The solvent accumulation effects strongly affected the scaling behavior of the domain spacing and the matrix domain length when the order-disorder transition was approached. For the case of selective solvent, the influence of solvent selectivity, solvent content on ordered phase window, and the scaling behavior of the bcc structural sizes were examined. The increase of solvent selectivity, incompatibility of A/B segment and molecular weight of copolymer expanded the region of stable ordered SABCC from the results of constructed phase maps. It was found that unfavorable chain expelling occured and solvent partitions preferentially to favorable chain region as increasing the solvent selectivity from the predicted density profiles.
In the second part of this dissertation, the prediction of pore size for the nanoporous MSSQ thin films by templating amphiphilic block copolymers, polystyrene-block –poly(2-vinyl pyridine)(PS-b-P2VP), was investigated. The simplified model from SCMF theory provided a successful methodology to demonstrate the effects of the copolymer composition, the MSSQ/porogen interaction, and the porogen loading ratio on the microdomain spacing and pore diameter with the body-centered-cubic sphere phase. For approaching higher pore density and smaller closed pore size in the MSSQ porous thin film, more composition fraction of the prepared PS block (fPS) and appropriate thermal curing temperature as well as smaller
Subjects
奈米材料
自洽平均場理論
共聚物
Nanomaterials
Copolymer
SCMF
Type
thesis
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