Self-Assembled 2D Sheets of an Amphiphilic Sexiphenyl Exhibit Intense Polarized Blue Emission in the Solid State

Distinct from inorganic 2D nanomaterials (e.g., graphene, MoS2, etc,), self-assembled organic 2D materials are significant due to the unique advantages of fine structure tunability and functionality. Electronically and photofunctionally-active compounds (e.g., pentacene, p-sexiphenyl) are highly attractive for applications but are limited by difficult handling and the existence of only a few native structures of the compounds. Here, it is shown that a p-sexiphenyl derivative incorporated into 2D multilamellar sheets with chromophores oriented in the layers exhibits a significant polarization of photoluminescence. Highly emissive, amphiphilic sexiphenyl with hydrophilic/hydrophobic groups self-assembles at air-water interface with chromophore orientation in the resulting films being controlled by monolayer compression. Large-area multilamellar structures with p-sexiphenyl chromophores highly oriented against the 2D plane are prepared by consecutive film transfers. The 2D sheets exhibit significant polarization of photoluminescence with polarization ratio 0.8 between orthogonal in-plane axes. Notably, multilamellar structures cannot be established for the same p-sexiphenyl using thermotropic processing thus emphasizing the importance of the 2D sheet multilayer synthesis process. Amphiphile design can be applied for the tailored synthesis of large-area multilayered 2D sheets and used to construct highly efficient light-emitting devices. Self-assembled films of an amphiphilic sexiphenyl (ASP-1) exhibit significant polarization of photoluminescence emission with an interaxial polarization ratio of 0.8 based on controlled orientation of the sexiphenyl chromophores within the multilayered films. Transfer at the air-water interface is critical to establish the highly oriented chromophore structure within the highly emissive films. image