| 摘要: | 本實驗以導電性高分子聚(3-己烷基?吩)(poly(3-hexylthiophene), P3HT)為研究出發點，因P3HT可應用於有機場效電晶、有機太陽能電池與有機發光二極體，由於元件的設計與光電性質的需求不同，必須藉由實驗製程的方式控制P3HT所生成的介觀形貌。為了能具體掌握形貌變化，以利提升元件性能，研究方向將分為三個系統：均聚物P3HT、P3HT與絕緣高分子混摻及P3HT與絕緣高分子所形成之雙嵌段共聚物。
1.均聚物P3HT 系統：P3HT在溶液中的結晶不匹配成核成長，主要由濃度效應所影響。當P3HT濃度越高時，則溶液的過飽和度也就越高，有利於形成球晶網狀結構，其流體性質為凝膠；反之，當P3HT濃度越低時，則溶液的過飽和度也就越低，有利於形成纖維網狀結構，其流體性質為溶膠。然而，即使在極低的P3HT濃度下，依然形成網狀構造，因此，才發展出P3HT的混摻系統與雙嵌段共聚物系統，改善現有問題。
2.P3HT與絕緣高分子 混摻系統：鑒於均聚物P3HT的基礎，藉由混摻絕緣高分子聚(甲基丙烯酸酯) (poly(methyl methacrylate), PMMA)、聚苯乙烯 (polystyrene, PS)和聚(丙烯酸十八酯) (poly(stearyl acrylate), PSA)，因絕緣高分子的溶解度參數的不同，進而影響P3HT的結晶成核成長。當P3HT混摻過多的PMMA時，因兩高分子的不相容性，促使P3HT結晶不匹配成核成長，相當於提高過飽和度；換言之，當P3HT混摻PS或PSA時，因兩高分子具有相容性，可使P3HT形成單一且筆直的纖維，有利於應用於有機場效電晶體。
3.P3HT與絕緣高分子 雙嵌段共聚物系統：當P3HT與PSA形成雙嵌段共聚物時，因兩鏈段受化學鍵結，其介觀形貌受溶劑性質、硬桿/柔軟長度比和共聚物濃度影響。當P1和P2溶於苯甲醚時，可形成筆直且單一纖維，適合用於有機場效電晶體；當P3溶於苯甲醚時，高濃度下形成烤肉串狀(shish kebab)，但低濃度下，形成硬桿團聚物(rod aggregation)。另外，當使用甲醇/四氫?喃為共溶劑時，其溶劑性質為不良溶劑，使雙嵌段共聚物形成微米粒子(microparticle)，由纖維物結構所團聚而成，大幅增加了P3HT吸光能力，有利於應用在有機太陽能電池。
The research is to study the morphologies of poly(3-hexylthiophene)(P3HT) homopolymers and its block copolymers since these materials can be used as potential materials for applications such as organic field-effect transistors(OFET), organic photovoltaics(OPV) and organic light-emitting diodes(OLED). In order to fit the devices’ design and to well control the photoelectric properties, it is necessary to understand how to finely tailor the mesoscale structures of P3HT in solutions and thin films. In the thesis, three investigated systems were arranged as follows：
Crystallization of P3HT homopolymers at various fractions in anisole：P3HT crystallographic mismatch nucleation and growth in solution were dominated by effect of the polymer concentration in anisole. At high P3HT concentrations, the degree of supersaturation in solution can be easily reached upon cooling to form network-like structures. As a result, the solutions containing large mass fractions of P3HT were in a gel state. By contrast, at low P3HT concentrations, the degree of supersaturation was low. The low supersaturation led P3HT to form fibrillar networks that can be dispersive in solution. The networks are comprised of fibrillar bundles with a high density of tip- and side-branches. In order to reduce the tip- and side-branches to grow single P3HT fibers in solution, two strategies were designed.
Mixtures of P3HT and insulating polymers：Blending insulating polymers (PMMA, PS and PSA) with various solubility parameters can affect P3HT crystallographic mismatch nucleation and growth in anisole. At low P3HT concentrations in anisole, adding small amounts of PS, PMMA and PSA can reduce the densitiy of tip- and side-branches within P3HT crystallites and cause the growth of single P3HT fibers. However, at high P3HT concentrations, as large amounts of PMMA were added into the P3HT mixture, the incompatibility between PMMA and P3HT caused high degree of crystallographic mismatch nucleation and growth, giving rise to amorphous P3HT agglomeration in solution.
Morphological study of poly(3-hexylthiophene)-block-poly(stearyl acrylate), P3HT-b-PSA, block copolymers in organic solvents：The morphology of P3HT-b-PSA was controlled by three factors：solvent quality, rod/coil length ratio and copolymer concentration. For the block copolymers with short PSA chains, increasing the solvent quality and lowering the polymer concentration favored the gowth of single P3HT fibers. By contrast, for the block copolymer with long PSA chains in anisole, shish-kebab stuctures formed at high concentrations whereas rod-like aggregations grew at low concentrations. In methanol/THF mixtures, where THF is good for both P3HT and PSA, and methanol is poor for both P3HT and PSA, P3HT-b-PSA tends to form fiber agglomeration. |
