Measuring the Degree of Crystallinity in Semicrystalline Regioregular Poly(3-hexylthiophene)

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• 作者：Xiaobo Shen ; Weiguo Hu ; Thomas P. Russell
• 刊名：Macromolecules
• 出版年：2016
• 出版时间：June 28, 2016
• 年：2016
• 卷：49
• 期：12
• 页码：4501-4509
• 全文大小：393K
• 年卷期：0
• ISSN：1520-5835

文摘

By using a combination of wide-angle X-ray diffraction (WAXD), mass density, and p>13p>C solid-state nuclear magnetic resonance (NMR) measurements, a quantification of the absolute degree of crystallinity in regioregular poly(3-hexylthiophene) (rr-P3HT) is presented. A regiorandom P3HT (rra-P3HT), lacking long-range order, was used to separate the crystalline contribution from the total scattering in WAXD, thus yielding degrees of crystallinity in the range of 47–56% at room temperature for three different rr-P3HTs. For the same rr-P3HT with identical processing history, NMR yields degrees of crystallinity that are consistently ∼10% greater than that obtained by WAXD, which can only be explained by ordered chain segments in the amorphous phase. NMR results also suggest that rra-P3HT contains weakly ordered chain segments, which likely contribute to an underestimation of degree of crystallinity when determined from mass density measurements, if rra-P3HT is used to approximate a fully amorphous P3HT. The results shown in this study provide direct proof of three different types of P3HT chain segments: crystallites (i.e., long-range ordered chain packing), amorphous phase (i.e., disordered chain packing), and short-range ordered chain packing embedded in the amorphous phase. The presence of the short-range ordered chain packing is particularly important when correlating the morphology to macroscopic charge transport properties in P3HT-based devices. In general, those locally ordered chain segments, though not constituting a distinct phase, are believed to be of critical importance in determining the transport characteristics of conjugated semiconducting polymers with or without a distinct crystalline phase present.