We demonstrate a systematic visualization of the unique photophysical and fluorescence anisotropic properties of polyfluorene coplanar conformation (β-conformation) using time-resolved scanning confocal fluorescence imaging (FLIM) and fluorescence anisotropy imaging microscopy (FAIM) measurements. We observe inhomogeneous morphologies and fluorescence decay profiles at various micrometer-sized regions within all types of polyfluorene β-conformational spin-coated films. Poly(9,9-dioctylfluorene-2,7-diyl) (PFO) and poly[4-(octyloxy)-9,9-diphenylfluoren-2,7-diyl]-co-[5-(octyloxy)-9,9-diphenylfluoren-2,7-diyl] (PODPF) β-domains both have shorter lifetime than those of the glassy conformation for the longer effective conjugated length and rigid chain structures. Besides, β-conformational regions have larger fluorescence anisotropy for the low molecular rotational motion and high chain orientation, while the low anisotropy in glassy conformational regions shows more rotational freedom of the chain and efficient energy migration from amorphous regions to β-conformation as a whole. Finally, ultrastable ASE threshold in the PODPF β-conformational films also confirms its potential application in organic lasers. In this regard, FLIM and FAIM measurements provide an effective platform to explore the fundamental photophysical process of conformational transitions in conjugated polymer.

Advanced thermal management materials with low thermal conductivity and robustness have been a research hotspot for energy conservation and sustainable development. However, the brittleness of inorganic materials and the high flammability of polymers remain a challenge for industrial applications. Herein, we demonstrated a novel strategy to fabricate an organic/inorganic composite aerogel based on a combination of hydroxyapatite (HAP) and chitosan (CS). The combination of chemical cross-linking and unidirectional freeze-drying methods can significantly improve the mechanical properties and thermal stability, and the obtained anisotropic microstructure has a significant effect on thermal conductivity. Compared with the uncross-linked HAP-Si/CS composite aerogel, the cross-linked HAP-Si/CSG composite aerogel has high mechanical strength (0.82–2.37 MPa) and high specific modulus (41.22–129.20 kN m kg–1). In addition, the as-prepared HAP-Si/CSG composite aerogel exhibits a lower radial-direction thermal conductivity (28.16–37.43 mW m–1 K–1) than that of the axial direction. Meanwhile, the composite aerogel constructed by the HAP nanostructure embedded in the CS sheets better limits the heat transfer and blocks the combustion of organic compounds, showing excellent fire resistance. Thus, the biomass-based composite aerogel will be a sustainable and renewable functional material with high mechanical properties and thermal insulation, which is further expected to promote the high-value utilization of biopolymers.

In this paper, we described a new category of solution-processible small molecule organic light emitting materialssthe pyrene-functioned diarylfluorenes: 2PPPF and DPPPF. In solution, both of the materials show deep blue emission. In film, their emission largely red-shifted due to strong π-π stacking of pyrene groups. 2PPPF, which is quite rigid in molecular structure, bearing only one alkoxyl group, could form smooth film by spin-coating. From the photoluminescence and morphology study, we believe the strong π-π stacking enhanced the film forming ability. 2PPPF is an amorphous blue light emitter, with a T g over 100 °C and T d over 430 °C. The good thermal stability is comparable to polymeric light emitting materials. The material shows strong aggregated emission with a broad structureless peak at about 460 nm in film. Electroluminescent devices by spin-coating were successfully fabricated. A single-layered device using 2PPPF as the active material shows a turn on voltage of 4.3 V, brightness over 3600 cd/m 2 , and current efficiency up to 1.30 cd/A. When 2PPPF was blended into PVK, the single-layered device takes on deep blue emission with the CIE 1931 coordinates at (0.16, 0.10). Single-layered white organic light emitting diodes using 2PPPF:MEHPPV blend as the bulk emitter had a maximum current efficiency up to 1.84 cd/A and brightness over 5700 cd/m 2 .