Side-Chain Dynamics and Crystallization in a Series of Regiorandom Poly(3-alkylthiophenes)

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• 作者：Shireesh Pankaj ; Elke Hempel ; Mario Beiner
• 刊名：Macromolecules
• 出版年：2009
• 出版时间：February 10, 2009
• 年：2009
• 卷：42
• 期：3
• 页码：716-724
• 全文大小：240K
• 年卷期：v.42,no.3(February 10, 2009)
• ISSN：1520-5835

文摘

A series of regiorandom poly(3-alkylthiophenes) [P3ATs] with 4 ≤ C ≤ 12 alkyl carbons per side chain are studied by shear, calorimetry, X-ray scattering techniques, and infrared spectroscopy. We show that the tendency of alkyl groups to segregate in small alkyl nanodomains is a common feature of semicrystalline and amorphous members of this series. Semicrystalline poly(3-dodecylthiophene) (C = 12) samples show a pronounced lamellar structure with a coherence length of about 150 Å, corresponding to staples of main chain and alkyl nanodomains comparable to the findings for regioregular P3ATs, while the alkyl nanodomains in amorphous P3ATs have more irregular shape and boundaries. An additional relaxation process α_PE, which is related to the dynamics of CH₂ units in the alkyl nanodomains, appears in amorphous samples with C ≥ 6. Its frequency temperature dependence is very similar to that of the α_PE process found in other side-chain polymers containing alkyl groups with identical length. This is a strong argument supporting the idea that main chains and alkyl groups separate in amorphous systems. Another interesting finding is the appearance of three distinct melting peaks for regiorandom poly(3-dodecylthiophene) [P3DDT] at temperatures between −10 and 50 °C. Isothermal crystallization experiments are performed, and possible reasons for the appearance of three distinct melting peaks are considered. Similarities and differences between regiorandom and regioregular P3ATs in the semicrystalline state are described and discussed on the basis of their microstructure.