Self-Assembling Hierarchical Structure-within-Structure System of Rod-Comb Block Copolymer Supramolecular Complexes
Date Issued
2009
Date
2009
Author(s)
Weng, Shih-Chun
Abstract
I studied the supramolecular rod-comb block copolymers formed by complexa- -tion of an amphiphilic surfactant , dodecylbenzenesulfonic acid (DBSA) , with the poly(2-vinylpyridine) (P2VP) blocks in a rod-coil block copolymer , poly(phenylene vinylene)-b-poly(2-vinyl pyridine)(PPV-b-P2VP). The rod-coil copolymer complexes exhibited structure-within-structure morphology. On the larger block copolymer lenth scale , the PPV blocks are microphase-separated from the P2VP(DBSA)x blocks and the smaller-scale lamellar mesophase organized by the P2VP(DBSA) comb blocks. This thesis is dedicated to resolving the hierarchical structures of the rod-comb PPV-b-P2VP(DBSA)x supramolecular system. Small angle X-ray scattering (SAXS), wide angle X-ray scattering (WAXS) , transmission electron microscopy (TEM) and polarized optical microscopy (POM) have been used for the structure characterization. In particular, temperature-dependent SAXS and WAXS have been utilized to probe the thermally-induced phase transition processes such as order-order transition (OOT) and order-disorder transition (ODT). The effects of copolymer composition with volume fraction,f , of P2VP blocks of 0.27 and 0.52) and the complex compositon have been systematically investigated. In f=27-PPV/2VP(DBSA)x systems. For x=0.5 and x=1.0, the rod-comb diblocks copolymer both exhibited a lamellar-within-lamellar morphology. But when x=1.0, the block copolymer exhibits a lamellar structure with two length scales . The larger one consists of fully-stretched P2VP chain in a P2VP(DBSA) bilayer and the other one consists of fully-stretched P2VP chain in a P2VP(DBSA) single layer which was assumed to be alleviating system’s free energy. n f=52-PPV/2VP(DBSA)x systems. For x=0.143,0.4 and 0.6, the system’s morphology changes from a lamellar structure with only one length scale to lamellar-within-lamellar hierarchical structures. For x=0.8, a phase transformation reaction occurs and the resulting morphology can not be reaily defined. For x=1.0, the rod-comb diblocks copolymer exhibtd a cylinder-within-lamellar morphology, where the PPV cylindrical domain of ca. 8.2nm in diameter embedded in the matrix consisting of the lamellar mesophase with the interlamellar distance of ca. 2.9nm organized by the P2VP(DBSA) comb block.
Subjects
block copolymer
comb-like polymer complex
hierarchical structures
structure-within-structure
dodecylbenzenesulfonic acid
Type
thesis
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