Preservation of photoluminescence efficiency in the ordered phases of poly(2,3-diphenyl-1,4-phenylenevinylene) via disturbing the intermolecular χ-χ Interactions with dendritic aliphatic side chains

Yu Chun Wu, Xiang Kui Ren, Er Qiang Chen, Hsun Mei Lee, Jean Luc Duvail, Chien-Lung Wang*, Chain-Shu Hsu

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

5 Scopus citations

Abstract

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-P3, 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-hydrophilic natures of the side chains show strong effects on photophysical properties of the polymers. The solutions and as-casted films of P1-P3 all show remarkably high photoluminescence (PL) efficiency (Î PL) (>80% in chloroform solution, and >63% for the as-casted films). However, Î 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 PL can be elucidated and attributed to the ordering of the solid-state structures of P1 and P3. To our surprise, 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 χ-χ interactions among the conjugated backbones, which allows the preservation of 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.

Original languageEnglish
Pages (from-to)4540-4549
Number of pages10
JournalMacromolecules
Volume45
Issue number11
DOIs
StatePublished - 12 Jun 2012

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