以苯甲醛改質末端基之P3HT與雙親性P3HT共聚高分子製備P3HT/TiO2奈米複合材料

Abstract

在本論文中，我們分別以苯甲醛改質末端基之P3HT (P3HT-CHO)與雙親性P3HT共聚高分子 (poly(3-hexylthiophene-block-hydroxylated isoprene), P3HT-b-PIOH) 製備P3HT/TiO2奈米複合材料，並對其微結構與光學性質進行探討，我們採用了兩種方法製備複合材料: (1)將高分子溶液直接與TiO2奈米粒子(Degussa P25)進行攪拌混摻; (2)以in-situ溶凝膠法在高分子溶液中製備TiO2奈米粒子。 藉由P3HT-CHO的醛基與P25表面上氫氧基之間的吸引力，奈米複材中TiO2的聚集約在50至200奈米左右，而在in-situ溶凝膠法中，TiO2的前驅物chlorotitanium triisopropoxide (CTIP)可以與P3HT-CHO的醛基進行共價反應，使得P3HT-CHO被固定在TiO2表面，進一步改善TiO2在奈米複材中的散佈情形，但得到的TiO2奈米粒子大小也約在50至200奈米之間。而在溶凝膠法的製備過程中，因為不存在分散劑與ligand的關係，光激發螢光的強度也會下降，代表有較好的電子轉移效率。 在使用P3HT-b-PIOH/ClTIP製備的奈米複材中，我們可以得到均勻分布於高分子基質且尺寸大小均在30奈米的TiO2奈米粒子，這是因為PIOH上具有更多的親水性練段能與TiO2表面進行共價反應所致。 光學性質的部分則是以UV-vis光譜測量，即使TiO2的添加量達到了30 wt%，在P3HT-CHO/ClTIP及P3HT-b-PIOH/ClTIP的奈米複材中，其P3HT吸收峰均未見藍移的情形，並可觀察到π-π stacking 的吸收峰值訊號。

In this thesis, we reported the preparation, the microstructures and the optical properties of poly(3-hexylthiophene)/TiO2 nanocomposites based on aldehyde end-functionalized P3HT (P3HT-CHO) and amphiphilic P3HT block copolymer, poly(3-hexylthiophene-block-hydroxylated isoprene) (P3HT-b-PIOH). Pristine unmodified P3HT were also used for reference studies. Two methods were employed to prepare the Nanocomposites: (1) solution blending of polymers and commercial available TiO2 nanoparticles, Degussa P25 (~21 nm); (2) in-situ sol gel process of TiO2 precursors in polymer solution. The attractive interaction between aldehyde of P3HT-CHO and hydroxyl group of TiO2 allowed smaller aggregations of TiO2 (~ 50 - 200 nm) blending.The in-situ sol gel processes using chlorotitanium triisopropoxide (ClTIP) would further enhance the homogeneity in TiO2 dispersion despite of enlarged particle sizes (~ 50 -200 nm) as the aldehyde group of P3HT-CHO would react with ClTIP to form covalent bonds to anchor P3HT in the surface of TiO2. Thus preventing the aggregation of TiO2. Since the in-situ sol gel process avoid the use of dispersants and ligands of TiO2 nanoparticles, the photoluminescence quenching of P3HT-CHO/ClTIP composites could be further improved comparing to P3HT-CHO/P25. The use of amphiphilic P3HT-b-PIOH block copolymer remarkably afforded the resulting P3HT-b-PIOH/ClTIP composites having uniformed TiO2 nanoparticles (~ 30 nm) homogenously dispersed in the polymer matrix, which could be attributed the increasing number of covalent linkages between the hydroxyl groups of PIOH and ClTIP. The optical properties were derived from the UV-vis spectroscopy. Even the loading of TiO2 was up to 30 wt%, the maximum absorption peak was not blue-shifted and the π-π stacking of P3HT retain for P3HT-CHO/ClTIP and P3HT-b-PIOH/ClTIP composites