Polarized
fluorescence of oriented N-salicylideneaniline
(SA) derivatives is explored based on the thermally stimulated photoinduced
molecular reorientation of liquid crystalline (LC) copolymethacrylate
with N-benzylideneaniline derivative (NBA2) and benzoic
acid (BA) side groups. The LC copolymer films show significant cooperative
molecular reorientation of the NBA2 and BA side groups (D > 0.7). Subsequent thermal hydrolysis of the NBA2 side groups
yields
free phenylamine moieties. These moieties can form oriented SA derivatives
via in situ condensation with 2-hydroxybenzaldehyde
derivatives. The excited-state intermolecular proton transfer of the
oriented SA molecules induces polarized fluorescence at 510–548
nm with a polarization ratio up to 6.2. Direct in situ exchange from the oriented NBA2 to SA derivatives achieves polarized
fluorescence similar to that of the SA side groups.
Thermally stimulated photoinduced reorientation of liquid crystalline (LC) polymethacrylate composed of a phenyl benzoate mesogen connected with N-benzylideneaniline (NBA2) end moiety exhibits a significant molecular reorientation (D > 0.7) when the film is exposed to linearly polarized 313 nm light and subsequently annealed in the LC temperature range of the material. Hydrolysis of the NBA2 end moieties yields an oriented mesogen with phenylamine moieties without distorting the oriented structure. In situ condensation of 2-hydroxybenzaldehyde derivatives and phenylamine moieties yields oriented N-salicylideneaniline side groups. The resultant film displays a polarized fluorescence with a polarization ratio up to 3.4.
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