| Summary: | 碩士 === 國立中央大學 === 化學工程與材料工程學系 === 102 === Organic devices have attracted great interests due to their advantages of low cost, solution-based processes, and flexibility. Poly(3-hexylthiophene)(P3HT), as a typical linear conjugated polymer, have been applied in commercial processes.
In this study, we focused on the conformation of P3HT chains in three organic solvents of different selectivity. The chain conformation in the dilute solutions affected the morphology in solid state. By controlling the composition of binary co-solvent mixtures, the drive force of P3HT aggregation can be finely tuned.
THF is a good solvent for the thiophene backbone and but a poor one for the 3-hexyl side chain. In contrast, the affinity of cyclohexane shows an opposite trend, being good for 3-hexyl side chains but poor for the thiophene backbone. The selectivity of toluene lies between THF and cyclohexane. Next I added a series of alcohols with different CH2 length to tune the solvent quality to form P3HT aggregates with different nanostructures in solutions.
UV-vis and PL measurements were used to identify the correlations between solvent quality and the degree of ordering in aggregates. AFM and GIWAXD characterizations were carried out to investigate the P3HT morphology and the degree of crystallization in solid state. As the polarization of alcohols increased, the aging rate increased. the nearest-neighbor inter-chain coulombic coupling J0 did not significantly change. J0 is sensitive to the selectivity of solvents and the ratios of alcohols in binary co-solvent mixtures.
P3HT aged quickly in the solvent mixture of THF/alcohols and formed large-sized aggregation structures with disorder orientation. In the solvent mixtures of toluene/ alcohols (except for toluene/1-propanol), P3HT formed single fibers and well dispersed. In contrast, P3HT in the cosolvent mixtures of cyclohexane/alcohols was found to form bundles of nano-sized fibers with high orientational ordering.
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