Crystal Structure and Molecular Packing Behavior of Poly(2,3-diphenyl-1,4-phenylenevinylene) Derivatives Containing Alkyl Side-Chains

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• 作者：Xiang-Kui Ren ; Yu-Chun Wu ; Shao-Jie Wang ; Shi-Dong Jiang ; Jun-Feng Zheng ; Shuang Yang ; Er-Qiang Chen ; Chien-Lung Wang ; Chain-Shu Hsu
• 刊名：Macromolecules
• 出版年：2013
• 出版时间：January 8, 2013
• 年：2013
• 卷：46
• 期：1
• 页码：155-163
• 全文大小：515K
• 年卷期：v.46,no.1(January 8, 2013)
• ISSN：1520-5835

文摘

Phase behavior and crystal structure of a series of poly(2,3-diphenyl-5-alkyl-p-phenylenevinylene) (denoted as DPn-PPV, where n represents the carbon number of the alkyl side-chain, n = 6, 8, 10, 12) were studied using differential scanning calorimetry, one- and two-dimensional (1D and 2D) wide-angle X-ray diffraction (WAXD), and selected area electron diffraction (SAED). The experimental results reveal that DPn-PPV exhibits one crystalline phase at low temperatures. On the basis of 2D WAXD and SAED patterns obtained from the oriented samples, the crystal structures are determined to be orthorhombic for DP6-PPV and monoclinic for DP8-PPV, DP10-PPV, and DP12-PPV. To account for the unusually large unit cell dimensions, we propose that the unit cell of DPn-PPV contains 4 chains (8 chemical repeat units). The complex crystal structure can be attributed to the longitudinal and transverse offsets between the neighboring chains, which shall be mainly due to the requirement of minimizing the steric hindrance caused by the attached pendent groups and maximizing the 蟺鈥撓€ interaction between the chains. The molecular packing scheme was simulated by using Cerius² software, of which the result agrees with the experimental data. The polarized UV鈥搗is absorption and polarized solid-state photoluminescence (PL) property of these polymers was also investigated. The PL spectra indicated that the light emitted from the oriented film was preferentially polarized parallel to the shear direction, implying that DPn-PPV may potentially be useful in linearly polarized luminescence devices.