Aggregation-Induced Energy Transfer in Color-Tunable Multiblock Bottlebrush Nanofibers

Abstract

The synthesis of multicomponent nanoscale structures with precisely addressable function is critical to the discovery of both new phenomena and new applications in nanotechnology. Though self-assembly offers low-cost routes to many such materials, these methods often require building blocks with particular structural motifs, thus limiting the scope of nanomaterials that can be prepared in these ways. Herein we use a bottom-up approach based on covalent chemistry to synthesize a series of bottlebrush copolymers from red, green, and blue luminescent macromonomers, which were then used to prepare multiblock organic nanofibers structurally analogous to nanoscale RGB pixels. Efficient energy transfer from a blue fluorophore to red and green phosphors can be modulated, using the solvent polarity as a stimulus, to give aggregation-induced changes in emission color. Aggregation was also accompanied by changes in the emission lifetime of the nanofiber from the nanosecond to microsecond regime. Additionally, changes in energy transfer efficiency and interchromophore distance were quantified using a FRET model. Preliminary demonstration of these materials as polarity-sensitive inks for encryption and encoding were also demonstrated using a red/blue fluorescence switch upon exposure to solvent. Finally, the potential complexity of optoelectronic materials accessible with these methods was demonstrated by combining these building blocks with charge-transporting materials to give organic nanofibers with ordered structures mimicking that of multilayer white OLEDs. Ultimately this work describes the preparation of robust, multicomponent nanofibers from general building blocks, combining their optoelectronic properties in ways that can be both reversibly switched and temporally resolved.

Surfactant‐Induced Interfacial Aggregation of Porphyrins for Structuring Color‐Tunable Liquids

“…While the components comprising these “structured liquids” can integrate their own inherent functionality, the jamming of nanoparticles at the interface can transform the fundamental nature of the assemblies, as demonstrated with the recent discovery of ferromagnetic liquid droplets where magnetic nanoparticles are used [33] . Chromogenic materials open further opportunities to generate responsive all‐liquid constructs that can act as sensory devices but also provide unique opportunities to gain fundamental insights into assemblies of the nanoparticles at the fluid interface that form the basis for structuring the liquids [34–41] …”

The Impact of Aggregation on the Photophysics of Spiro‐Bridged Heterotriangulenes

“…At proximity,t he molecular building blocks favor the formation of either excimers or exciplexes with emissive features significantly different from those of the individual components. [7,21,22] Strongly distance-dependent deactivation processes such as excited-state energy, [20][21][22][23][24] charge, [25] and electron transfer [23] are facilitated between molecules in confined space.T he lack of molecular rotations leads to aggregation-induced/ -enhanced emission, which strongly favors radiative deactivations. [24,[26][27][28][29] Herein, we present asystematic study of the properties of aseries of related heteroatom-containing polycyclic aromatic hydrocarbons-namely spirofluorene-bridged triarylamine, [30] -phosphine,and phosphine oxide [31] -in the transition from molecular species to large aggregates ( Figure 1).…”

“…At proximity, the molecular building blocks favor the formation of either excimers or exciplexes with emissive features significantly different from those of the individual components . Strongly distance‐dependent deactivation processes such as excited‐state energy, charge, and electron transfer are facilitated between molecules in confined space. The lack of molecular rotations leads to aggregation‐induced/ ‐enhanced emission, which strongly favors radiative deactivations …”

Der Einfluss von Aggregation auf die Photophysik von spiroverbrückten Heterotriangulenen

“…[16][17][18][19][20] Im angeregten Zustand hingegen ergeben sich viel komplexere photophysikalische Phänomene.D ie Nähe der molekularen Bausteine ermçglicht die Ausbildung von Excimeren und Exciplexen, deren Emissionsverhalten sich grundlegend von dem der Einzelkomponenten unterscheidet. [7,21,22] Stark distanzabhängige Deaktivierungsprozesse,w ie Energietransfer im angeregten Zustand [20][21][22][23][24] sowie Ladungs- [25] oder Elektronentransfer [23] werden durch den geringen Abstand begünstigt. Die Unterdrückung molekularer Rotationsbewegungen hingegen erlaubt eine Verstärkung strahlungsbehafteter Deaktivierungen durch aggregationsinduzierte/-verstärkte Emission.…”