Impact of Thermal Annealing on the Semicrystalline Nanomorphology of Spin-Coated Thin Films of Regioregular Poly(3-alkylthiophene)s as Observed by High-Resolution Transmission Electron Microscopy and

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• 作者：Shabi Thankaraj Salammal ; Eduard Mikayelyan ; Souren Grigorian ; Ullrich Pietsch ; Nils Koenen ; Ullrich Scherf ; Navaphun Kayunkid ; Martin Brinkmann
• 刊名：Macromolecules
• 出版年：2012
• 出版时间：July 10, 2012
• 年：2012
• 卷：45
• 期：13
• 页码：5575-5585
• 全文大小：823K
• 年卷期：v.45,no.13(July 10, 2012)
• ISSN：1520-5835

文摘

The impact of thermal annealing on the growth of crystalline nanodomains of poly(3-alkylthiophene) (P3AT) in thin films (15鈥?0 nm thick) was investigated as a function of length of alkyl side chain by combined low-dose high-resolution transmission electron microscopy (HR-TEM) and grazing incidence X-ray diffraction (GIXD). Statistical analysis of the data yields the characteristic dimensions of the face-on oriented P3AT nanocrystals, i.e., average stem length l_c along backbones and lateral dimension perpendicular to the stems l_a along side chains. The following trends were identified: (i) in as-spin-coated films, the proportion of face-on oriented nanocrystals increases with the number of carbon atoms in the side chain, (ii) annealing favors the lateral in-plane growth of the nanocrystals along the side chain direction (a_P3AT axis), (iii) for a given P3AT, the proportion of face-on oriented domains increases with annealing temperature, (iv) lateral growth along the a_P3AT axis is most efficient for the longer octyl side chains, and (v) thermal annealing induces only modest lamellar thickening which is limited by the poor slide diffusion of 蟺-stacked P3AT chains as opposed to lateral growth favored by weak van der Waals interactions between layers of n-alkyl side chains. The increase in the population of face-on oriented crystallites, observed when the length of the side chain increases, coincides with a corresponding decrease in the field effect mobility in annealed P3AT thin films.