Self-Consistent Mean Field Theory of Lyotropic AB Star Copolymers
Date Issued
2007
Date
2007
Author(s)
Sung, Yi-Lin
DOI
en-US
Abstract
Lyotropic block copolymers have become new approaches for preparing nano-materials with delicate, accessible self-assembled morphologies. Their amphiphilic property is very similar to surfactants’. However, the chain length of the polymers could be hundred times more than the surfactants. So that it is much easier to develop the self-consistent field theory (SCFT) to calculate the copolymer phase diagram than the surfactants. In this thesis, SCFT is employed to analyze the phase behavior of lyotropic star copolymers with different solvent systems.
In the first part of this thesis, we present the theoretical derivation of the SCFT for AnBm copolymers with solvent from the full classical partition function of this system. We extend the recent SCFT scheme of Matsen, which was developed to study the polymer phase behavior of melts, to solve the partition function by spectral method. We present an algorithm for the SCFT of block copolymers within a specific class of multiple arms chain architecture.
In the second part of this thesis, we calculate the common mesophases for the ABm star copolymers. Interestingly, we also find a new mesostructure for the ABm star copolymers. By changing the arm number of solvophilic B, we construct numerically the phase diagrams and try to locate the precision phase boundary between the lamellar, the hexagonal and the micelle phases. We discuss the microstructures of star copolymers, which are affected by the copolymer architecture, and the solvent concentration. We try to explain the results for phase transitions by the idea comes from the surfactant packing parameter. The ratio of the ABm copolymer volume to the cross-section of the B-head and the height of the copolymer is similar to the critical packing parameter of surfactants. We study the micelle melting in the dilute region and find that the single polymer solubility is increased as the arm number of B increases.
Subjects
自洽場
星狀共聚物
SCFT
Lyotropic copolymer
multiarm
Type
thesis
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