利用溶膠凝膠法製備P3HT-TiO2複合材料與其性質探討

Abstract

In this study, poly(3-hexylthiophene) (P3HT) and TiO2 composites are prepared from in-situ sol gel processes in a solution of amphiphilic P3HT-block-poly(hydroxylated isoprene) (P3HT-b-PIOH) using titanium tetraisopropoxide (TTIP) as the precursor for TiO2. The loading, size and distribution of TiO2 in the composites as well as the morphologies and the crystallinity of the bulk composites are evaluated. A series of diblock copolymers P3HT-b-PIOH (denoted as D1, D2) and triblock copolymers PIOH-b-P3HT-b-PIOH (denoted as T1, T2) with comparable molecular weights and compositions are synthesized to systematically study the effect of composition and molecular architecture on the microstructure of the composites. For the composites of T1and T2 with less than 12 wt% of TiO2, uniformly dispersed TiO2 nanoparticles with 20-40nm are observed while the homogeneity could only be achieved in the composites of D1, D2 with less than 4.5 wt% of TiO2, suggesting triblock copolymers would have better capability to disperse TiO2 than the corresponding diblock copolymers. Longer PIOH in T2 and D2 also offer better dispersion of TiO2 in the corresponding composite. The microphase separated nanostructure of D1 and D2 retained after the introduction of TiO2 in the corresponding composites. However, the microphase separation of T2 disappeared after the addition of small amount of TiO2. The incorporation of TiO2 is found to significantly suppress the crystallinity of P3HT originated from hexyl side chain interdigitation, as suggested by the remarkably decreased melting and crystallization enthalpies retrieved from DSC curves as well as much weaker diffraction signals in the WAXS patterns of the composites. The crystallinity of the triblock copolymer composites almost disappeared completely. Thermal annealing above the melting temperature of P3HT could improve neither the long range order of mirophase separation nor the crystallinity for the triblock copolymer composites, indicating small amount of TiO2 dispersed in PIOH-b-P3HT-b-PIOH with short PIOH would afford stable “amorphous P3HT composites”