Polydiarylfluorene Molecular Weight Effects on β-Conformation Formation for Amplified Spontaneous Emission for Optoelectronic Applications AITranslate

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DOI：https://doi.org/10.1021/acsapm.9b00451

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The hierarchical condensed structure of conjugated polymers (CPs) plays a key role in determining their optoelectronic property. Herein, we systematically explored the effect of molecular weight on the conformational and amplified spontaneous emission behavior of second generation β-conformational polyfluorene (PODPF). By analyzing the optical spectral analysis of PODPF from a single chain strand to its condensed state, including diluted toluene solutions and films, a favorable β-conformation in PODPF with a high molecular weight is exhibited. Interestingly, chain aggregation is a necessary but insufficient condition for the formation of the β-conformation in PODPF materials. Besides, high molecular weight PODPF (PODPF-H) adopted the large torsional angles for β-conformation that were inferred from the degree of red-shift in the photoluminescence (PL) spectra in the drop-coated and annealed films, which was further confirmed by the Raman spectra results at an increasing ratio of 1307 cm–1/1600 cm–1. A possible molecular weight “threshold” for PODPF is assumed to induce β-conformation formation. Finally, the formation of β-conformation can enhance the amplified spontaneous emission (ASE) behavior of PODPF. However, strong aggregation and rough film morphology can also induce relative high thresholds for PODPF-H annealed film. Therefore, Mn is an essential role in managing the chain behaviors, film morphology, and photoelectric properties of conjugated polymers.