Structure-within-Structure Morphologies of A2-star-(B-alt-C) Molecules in the Melts and Solution States
Date Issued
2008
Date
2008
Author(s)
Chang, Yu-Lung
Abstract
We employ the dissipative particle dynamics (DPD) to examine the self-assembly behavior of A2-star-(B-alt-C) molecules in the melt and solution regimes. In the melt, we successfully observe various types of hierachical structure-within-structures, such as B and C alternating layers in parallel-within-lamellae, coaxial B and C alternating domains within hexagonally packed BC-formed cylinders in the A-matrix, and co-centric BC-alternating domains within BC-formed spheres in the A-matrix, by increasing the A composition. We can find that when the copolymer chain length increases, though the hierachical structure type is maintained, the number of small-length-scale lamellae that can form within the large-length-scale structure increases and thickness of small-length-scale lamellae are not all the same. In the solution , various types of hierachical structure-within-structures, such as B and C alternating layers in parallel-within-lamellae, coaxial B and C alternating domains cladding with A within BC-formed cylindrical micelles, coexistent with coaxial B and C alternating domains cladding with A within BC-formed cylindrical micelles and co-centric BC-alternating domains cladding with A within BC-formed spherical micelles, co-centric BC-alternating domains cladding with A within BC-formed spherical micelles, coexistent with co-centric BC-alternating domains cladding with A within BC-formed spherical micelles and segmented worm-like micelles, segmented worm-like micelles are observed when an A-selective solvent is added. There are more variation of the self-assembly behavior in the solution regime than in the melt regime. The specially interesting is the sphere micelles variation from co-centric BC-alternating domains cladding with A within BC-formed spherical micelles to segmented worm-like micelles when totally polymerization increasing, alternating blocks polymerization increasing, A composition decreased and copolymers volume fraction decreased that we call them N effect, q effect, fA effect and
Subjects
coil-alternating molecule
dissipative particle dynamics
phase transitions
self-assembly
Type
thesis
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