A two-step, generally applicable synthetic approach for NLO
side-chain aromatic polyimides
was developed. This is a one-pot preparation of a preimidized,
hydroxyl polyimide, followed by the covalent
bonding of a chromophore onto the backbone of the polyimide via a mild
post-Mitsunobu reaction. NLO
side-chain aromatic polyimides with different polymer backbones and
different chromophores were
synthesized, and the chromophore loading level in the polyimides was
controlled efficiently from 0 to
50% by weight. This facile method provides the synthesis of NLO
polyimides with a broad variation of
polymer backbone and side-chain chromophores to fine-tune the
electrical and structural properties. All
the synthesized NLO side-chain polyimides have high glass transition
temperatures (T
g > 220 °C) and
thermal stability. A large electro-optic (E-O) coefficient
(r
33) value (11 pm/V measured at 0.83 μm
and
34 pm/V at 0.63 μm) and long-term stability (>500 h at 100 °C) of
the dipole alignment were observed.
A photoluminescence (PL)-based oxygen and glucose sensor utilizing inorganic or organic light emitting diode as the light source, and polythiophene: fullerene type bulk-heterojunction devices as photodetectors, for both intensity and decay-time based monitoring of the sensing element's PL. The sensing element is based on the oxygen-sensitive dye Pt-octaethylporphyrin embedded in a polystyrene matrix.
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