Preservation of Photoluminescence Efficiency in the Ordered phases of Poly(2,3-diphenyl-1,4-phenylenevinylene) via Disturbing the Intermolecular 蟺鈥撓€ Interactions with Dendritic Aliphatic Side Chains

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• 作者：Yu-Chun Wu ; Xiang-Kui Ren ; Er-Qiang Chen ; Hsun-Mei Lee ; Jean-Luc Duvail ; Chien-Lung Wang ; Chain-Shu Hsu
• 刊名：Macromolecules
• 出版年：2012
• 出版时间：June 12, 2012
• 年：2012
• 卷：45
• 期：11
• 页码：4540-4549
• 全文大小：496K
• 年卷期：v.45,no.11(June 12, 2012)
• ISSN：1520-5835

文摘

To understand the relation between the solid-state phase structures and the photophysical properties of poly(2,3-diphenyl-1,4-phenylenevinylene) (DP-PPV) derivatives, three DP-PPV derivatives, P1鈥揚3, were designed, synthesized via Gilch polymerization and characterized. Among the polymers, P1 is a reported highly emissive poly(2,3-diphenyl-5-hexyl-p-phenylenevinylene), and P2 and P3 are novel DP-PPV derivatives, which are purposely designed to bear hydrophobic and hydrophilic Percec-type dendrons as side chains. The bulkiness and hydrophobic鈥揾ydrophilic natures of the side chains show strong effects on photophysical properties of the polymers. The solutions and as-casted films of P1鈥?b>P3 all show remarkably high photoluminescence (PL) efficiency (桅_PL) (>80% in chloroform solution, and >63% for the as-casted films). However, 桅_PL of P1 and P3 decrease significantly to 30% after cooled their polymer melts to room temperature. Through the phase behavior analysis by differential scanning calorimetry (DSC), and phase structure analysis by wide-angle X-ray diffraction (WAXD), the decrease of 桅_PL can be elucidated and attributed to the ordering of the solid-state structures of P1 and P3. To our surprise, 桅_PL of P2 is preserved even in an ordered solid-state phase, and it is insensitive to the structural ordering. Structural analysis of P2 revealed that the aliphatic dendritic side chains of P2 effectively disturbing the intermolecular 蟺鈥撓€ interactions among the conjugated backbones, which allows the preservation of 桅_PL in the environment with ordered packing of DP-PPV molecules. The results of time-resolved PL decay experiments also confirmed that P2 possesses long-lived decay time because of excitons confined more effectively for emissive relaxation.