By means of molecular simulation, we propose possible packing models for £\ and £\¡¬ phases in poly(9,9-di-n-hexyl-2,7-fluorene) (PFH). Simulated multi-chain unit cell structures are compared with experimental diffraction patterns of PFH where the unit cell structure (and the space group) of the high-temperature £\ crystals was identified as monoclinic (C2) and that of £\¡¬ phase (kinetically favored upon programmed cooling) triclinic (P1). Results show that £\ phase prefers to adopt bi-radial side-chain conformation whereas the £\¡¬ phase prefers tetra-radial one. Both models exhibit embracing behavior between adjacent chains in spite of differences in inter-chain distance. A group of embracing chains aligned along b-axis in £\ phase and the comparatively greater inter-chain distance in £\¡¬ phase are consistent with the observed faceting along (100) planes and the tensile cracking along the a-axis. A qualitative analysis of co-existing £\ and £\¡¬ phases reproduce the [001] SAED pattern quite well. In addition, we also show that arbitrary alternation of 40o and 140o in dihedral angle between neighboring monomers generates equally stable single-chain conformations in this case of linear alkyl side-chains.
Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0613108-175959 |
Date | 13 June 2008 |
Creators | Hsieh, Cheng-Chang |
Contributors | Jrjeng Ruan, An-Chung Su, Michael Y. Chiang, Ming-Yu Kuo |
Publisher | NSYSU |
Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
Language | English |
Detected Language | English |
Type | text |
Format | application/pdf |
Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0613108-175959 |
Rights | unrestricted, Copyright information available at source archive |
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