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Article

Design, Synthesis, and Characterization of a −Donor−Bridge−Acceptor−Bridge- Type Block Copolymer via Alkoxy- and Sulfone- Derivatized Poly(phenylenevinylenes)

Supporting Info

Cheng Zhang,^† Soobum Choi,^† James Haliburton,^† Taina Cleveland,^† Rui Li,^† Sam-Shajing Sun,*^†^‡ Abram Ledbetter,^† and Carl E. Bonner^†^‡

Center for Materials Research and Chemistry Department, Norfolk State University, 700 Park Avenue, Norfolk, Virginia 23504

Macromolecules, 2006, 39 (13), pp 4317–4326

DOI: 10.1021/ma060179j

Publication Date (Web): June 3, 2006

†

Center for Materials Research, Norfolk State University.

In papers with more than one author, the asterisk indicates the name of the author to whom inquiries about the paper should be addressed.

‡

Chemistry Department, Norfolk State University.

Abstract

A novel class of light harvesting conjugated block copolymers, with electron-donating conjugated blocks (D) connected to electron-accepting conjugated blocks (A) via non conjugated and flexible bridge chains (B), has been designed, synthesized, and characterized. Specifically, D is a decyloxy-substituted polyphenylenevinylene (C₁₀−PPV). A₁ and A₂ are PPVs with sulfone (SO₂) acceptor moieties substituted on every other phenylene unit. A₁ carries two decyloxy groups on every phenylene unit, while in A₂, half of the phenylene units are unsubstituted. The optical energy gaps are 2.24 eV for the donor block (D), 2.33 and 2.45 eV for A₁ and A₂ acceptor blocks. LUMO level offsets are 0.24 and 0.16 eV for D/A₁ and D/A₂ pairs, respectively. Comparing the photoluminescence from both films and solutions, very large red shifts (71 and 74 nm for A₁ and A₂ respectively) were observed in the two acceptor polymers. These red shifts in the emission spectra were more than twice as much as that observed for D (31 nm). The (DBA₁B)_n and (DBA₂B)_n block copolymer films exhibited improved processability and optoelectronic properties when compared with the corresponding films composed of donor/acceptor blends. Atomic force microscopic (AFM) studies of D, A₁, and A₂ films were also undertaken to observe the degree of aggregation in the films. The results indicate the tendency of intermolecular aggregation increases as A₂ > D > A₁. AFM topological images revealed that large aggregates of several hundreds of nanometers formed in donor/acceptor blend films, while in block copolymer films, domain sizes were similar to individual block sizes which are 1 order of magnitude smaller than in the blend.