The Study On The Crystallization Of Poly(3-Alkylthiophene) And Its Composites

The crystallization behaviors of poly(3-alkylthiophene) and its compositions have been studied by a variety of characterization methods, such as infrared spectroscopy(IR), ultraviolet-visible spectroscopy(UV-Vis), atom force microscope (AFM), transmission electron microscope(TEM), wide-angle X-Ray diffraction (WAXD) and differential scanning calorimetry(DSC). Here poly(3-octylthiophene) and poly(3-hexylthiophene) are chosen as the main research objects for their structures.Firstly, the IR spectral variations and band assignments during the melting crystallization of P3OT at 165 ℃ have been investigated in detail. Several bands reflecting the structural order of the conjugated main chain have been disclosed. The decrease of the amorphous band at 835 cm-1 and the growths of the crystalline sensitive bands at 821 and 1506 cm-1 in a synchronized way, indicate that the ordering of interchain packing and conformational ordering of main chain take place at the same time during the crystallization process. Moreover, we have proposed a simple method to calculate the crystallinity approaching of P3OT based by utilizing the characteristic amorphous and crystalline bands in the spectral region of 850-800 cm-1. Avrami analysis on the isothermal melting-crystallization kinetics reveals that there are two distinct growth stages for the main-chain crystallization of P3OT, which is different from the traditional linear polymers.Secondly, the isothermal crystallization of P3HT/toluene solution at different temperatures and different shear forces has been studied by the home-made situ UV-Vis accessories, and the morphology and the structure of the formed nanowiskers have been characterized as well. It shows that the aggregates of P3HT changes with the temperature in the static isothermal crystallization. When the temperature is higher than 18℃, P3HT chains self-assemble into J aggregates; While when the temperature is lower, H aggregates are formed. Moreover, compared with static crystallization, dynamic crystallization by rotating shear force could promote the crystallization rate and degree, but it makes little effect on the aggregates form. The most importantly, this is the first time to find the sheet-like single crystals in the isothermal crystallization of P3HT solutions and this crystal modification is Form II crystals.Finally, the effect of a few crystalline polymer-poly (L-lactid) (PLLA) (0.1%-10%) on the the crystallization behaviors of P3HT nanowiskers has been investigated. The results show that the aggregates of P3HT nanowisker would not be influenced by PLLA and its modification still remains Form I. However, the main chains crystallization of P3HT can be improved by PLLA.