Synthesis and Characterization of Poly(3-hexyl thiophene) Based Rod-Coil Block Copolymers
Date Issued
2005
Date
2005
Author(s)
Cheng, Shih-Tzu
DOI
en-US
Abstract
Rod-coil block copolymers have been extensively studied recently since they offer the opportunities of tuning the morphologies and the resulted functionalities. Conjugated polymer based rod-coil block copolymers could tune the electronic and optoelectronic properties through the solvent quality or solid-state packing. For example, polyquinoline-polystyrene block copolymers could have various kinds of morphologies with tunable optical absorption or photoluminescence properties. Nanowires obtained from poly(3-hexyl thiophene)–coil block copolymers was also discovered recently. However, the effects of hydrophilic coil segment, solvent quality or processing temperature on the conjugated rod-coil block copolymers have not been fully explored yet.
In this thesis, synthesis, morphologies and properties of polythiophene based rod-coil block copolymers are reported. There are three parts of this thesis as shown below: (1) Synthesis of poly(3-hexyl thiophene) (P3HT) based rod-coil polymers by atom transfer radical polymerization. Three kinds of hydrophilic coil segments were employed, including poly(methyl methacrylate), poly(acrylic acid), and poly(3-(trimethoxysilyl)propyl methacrylate). The P3HT macroinitiator was synthesized first and then the coil segment was prepared using atom transfer radical polymerization. (2) Morphologies and properties of P3HT, (P3HT)47-b-(PMMA)748, (P3HT)47-b-(PAA)93 and (P3HT)47-b-(PMSMA)34 in solutions. The effects of good/poor solvent ratio on the morphologies and photophysical properties of the synthesized polymers were investigated. (3) Morphologies and properties of P3HT, (P3HT)47-b-(PMMA)748, and (P3HT)47-b-(PMSMA)34 in solid state. The effects of processing temperature on the morphologies and photophysical properties of the synthesized polymers were investigated.
The TEM results suggest that various morphologies of the (P3HT)47-b-(PMMA)748, (P3HT)47-b-(PAA)93 and (P3HT)47-b-(PMSMA)34 could be obtained by varying the good solvent toluene /poor solvent methanol ratio, including cylinder, sphere, vesicle, and large compound micelles (LCMs). The aggregation of the P3HT segment in the poor solvent of methanol explains the above result. Such aggregation led to a significant red shift on the optical absorption and photoluminescence spectra of the P3HT-coil block copolymers by increasing the methanol content in mixed solvents. The morphologies and photophysical properties of the (P3HT)47-b-(PMMA)748, (P3HT)47-b-(PAA)93 and (P3HT)47-b-(PMSMA)34 films were also significantly varied by the curing temperature. Blue shifts on the optical absorption and photoluminescence spectra of the P3HT-coil block copolymer film were observed by increasing the curing temperature. It is probably because the degree of twisting thiophene rings is increased by increasing the curing temperature. Thus, a coiled polythiophene chain with shorter conjugation lengths is obtained, which explains the variation of the photophysical properties with curing temperature.
The present study suggests that the morphologies and photophysical properties of the P3HT-coil block copolymers could be significantly tuned by the solvent quality or curing temperature.
Subjects
聚噻
吩
Poly(3-hexyl thiophene)
Rod-Coil Block Copolymers
Type
thesis
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