[15a-416-1~10] 12.3 Functional Materials and Novel Devices

[15a-416-10] Thermochromism for P3HT nanoparticles by re-precipitation

〇Kota Suetsugu¹, Hara Mitsuo¹, Nagano Shusaku², Shito Keiji³, Sato Toshimitu³, Masuhara Akito³, Seki Takahiro¹ (1.Grad. Sch. of Eng. Nagoya Univ., 2.Nagoya Univ. VBL, 3.Grad. Sch. of Sch. of Sci. and Eng. Yamagata Univ.)

Keywords:nanoparticle, thermochromism, re-precipitation

Reprecipitation method, very easy and useful to prepare nanoparticles, can provides monodisperse dispersions of nanoparticles by only injecting dilute solution into a poor solvent under agitation. We prepared nanoparticle dispersions of regioregular poly(3-hexylthiophene) (P3HT) with different molecular weight by reprecipitation method. Particle diameters of the nanoparticles were estimated a few tens of nanometers by both of dynamic light scattering measurement and scanning electron microscope observation. UV-vis absorption spectra of the P3HT dispersions were measured under temperature control. Absorption bands corresponding to the P3HT crystalline phase were observed in r.t. As temperature increase, the crystalline bands were decreased and the band due to the P3HT solution was increased. The absorption spectrum of the P3HT dispersions was almost the same as that of the P3TH solutions at 90°C. There thermal spectral change was reversible. Hence, the P3HT nanoparticle dispersion exhibited the thermochromic behavior. We divided the absorption spectra of the P3HT dispersions at r.t. into four peaks by waveform separation. The four divided spectra exhibited absorption maxima at 442, 527, 556, and 606 nm, respectively. The P3HT solution exhibits absorption maximum at 442 nm. Crystallinities of the P3HT nanoparticles were estimated by comparing the area at the peak of 442nm between the spectra at 25 and 90°C. The estimated crystallinities were dependent on molecular weight of P3HT. However, the particle sizes of the P3HT nanoparticles were almost independent of their absorption spectra and crystallinity. On the other hand, by changing poor solvent in represipitation, the crystallinities of nanoparticles and thermochromic behavior were changed. Moreover, we will discuss the comparison of the crystallinity for nanoparticles and spincast films and the molecular orientations in the films cast from the dispersions.