低温退火结合自成核方法制备FormⅡ晶型聚(3-十二烷基噻吩)纳米纤维

Preparation of Form Ⅱ Poly (3-dodecylthiophene) Nano-Fibers Using Low Temperature Annealing and Self-Nucleation Method

聚(3-十二烷基噻吩)(P3DDT)在常用有机溶剂中具有良好的溶解性,这一特点决定了制备P3DDT纳米纤维/线相对困难且其晶体结构不易调控。利用低温退火结合自成核方法成功制备了P3DDT纳米纤维,并探究了自成核温度对P3DDT纳米纤维结晶性与晶型的影响。P3DDT溶液经过低温退火再室温结晶后,可以得到均匀分布的、产率较高的纳米纤维,在此基础上增加自成核步骤能够进一步提高纳米纤维的结晶度。红外光谱的结果证实经过低温退火及自成核后制备的样品晶型为FormⅡ晶型,而不是通常的FormⅠ晶型。变温红外测试进一步揭示了P3DDT纳米纤维在升温过程中首先由FormⅡ晶型转变为FormⅠ晶型,随后熔融的相态变化。此研究结果有望对包括P3DDT在内的聚(3-烷基噻吩)(P3ATs)纳米纤维/线的制备及多晶型调控提供思路。

It has been realized that condensed structure control over poly(3-alkylthiophenes)(P3ATs) at nanoscale is essential for the improvement of the properties of optoelectronic devices. The aggregation of P3ATs at nanoscale driven by interchain π-π interactions typically shows the one-dimensional nanowires (NWs) morphology. Poly(3-dodecylthiophene)(P3DDT) has good solubility in normal organic solvents. This characteristic makes the preparation of P3DDT nanofibers/wires relatively difficult and out of control. In order to improve the crystallinity of P3DDT in solvents, P3DDT nanofibers were successfully prepared by low temperature annealing and self-nucleation method in this work. The influences of self-nucleation temperature on the crystallinity and crystal modification of P3DDT nanofibers were investigated. The results show that the homogeneous and high yield nanofibers can be obtained after the P3DDT solution is annealed at low temperature and then crystallized at room temperature. On this basis, the additional self-nucleation step can further improve the crystallinity of nanofibers. The results of infrared spectra show that the samples obtained after low temperature annealing and self-nucleation result in Form Ⅱ modification rather than the typical Form Ⅰ. Temperature dependent infrared test further reveals the transformation of P3DDT nanofibers from Form Ⅱ crystal to Form Ⅰ, and then the phase transition in the subsequent melting. This work is expected to shed light on the preparation and polymorphic control of poly(3-alkylthiophene)(P3ATs) nanofibers/wires. The investigation results will benefit for the understanding of the crystallization behavior of conductive polymers, providing the theoretical guideline for the structural control of the P3ATs NWs as well as the optimization of the properties of the devices in industrial process.