Solvent-driven reorganization of poly(diphenylacetylene) in film and nanofiber by means of swelling method: solvent annealing effects on fluorescence emission properties and microstructures
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- Han, DH., Lee, WE., Kim, SJ. et al. Polym. Bull. (2012) 69: 49. doi:10.1007/s00289-011-0691-9
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Freeze-dried nanofiber (Fr-nanofiber), spin-coated film (Sp-film), and solvent-cast film (So-film) of poly[1-phenyl-2-(p-trimethylsilyl)phenylacetylene] (PTMSDPA) were prepared to investigate solvent-annealing effects on their FL emission properties and microstructures by the swelling method. Their FL emission bands at maximum intensity (λmax,FL) appeared at 525, 535, 540 nm, respectively. Their FL emission life times (τavr) were 0.489, 0.136, 0.130, respectively. In polarizing optical microscopy (POM) observation, the So-film showed a chevron texture on the surface, whereas Sp-film did not display any characteristic texture. The polarizing fluorescence microscopy images of the So-film converted in shadow when the polarizer angle changed from 0° to 90°. In XRD patterns, So-film showed a very sharp signal at a small angle of 6.9° with a corresponding lamellar layer distance of about 13 Å, whereas Sp-film did not show a sharp signal at the same angle. The FL intensity of PTMSDPA after annealing with ethanol under very slow evaporation more greatly decreased in turns of Fr-nanofiber (I/I0 0.38), Sp-film (I/I0 0.47), So-film (I/I0 0.86). FL emission spectra of Sp-film annealed with ethanol, hexane, and methanol under very slow evaporation were measured. Ethanol (I/I0 0.47) induced a greater decrease in FL emission intensity as compared to hexane (I/I0 0.78) and methanol (I/I0 0.65). POM, FL optical microscopy (FOM), and transmission electron microscopy (TEM) images as well as XRD patterns of Sp-film after ethanol annealing under slow evaporation were observed. The POM images and XRD patterns did not show any significant changes after solvent annealing while the FOM and TEM images certainly showed a little change. The FL emission of the film was weaker in the annealed part than in the non-annealed part. The annealed film exhibited several domains with certain lattice fringes of d space of ~3.6 Å, while the as-prepared film showed exclusively amorphous regions.