Two pyrenyl Schiff base derivatives with π conjugated
structures
(
B2
and
B3
) were designed and synthesized.
Then,
B2
and
B3
were added into polyurethane
to obtain doped and bonded polyurethane nonlinear optical materials
(
B2
/PU and
B3
/PU), respectively. The synthesized
B2
,
B3
, and polyurethane nonlinear optical materials
were tested by a nanosecond (ns) and picosecond (ps) pulse
Z
-scan at a 532 nm wavelength. Due to the two-photon absorption-induced
excited state absorption (TPA-ESA),
B2
,
B3
, and polyurethane nonlinear optical materials show reverse saturable
absorption (RSA). From a quantum chemistry calculation, it can be
concluded that the RSA of
B2
and
B3
comes
from the large π conjugated system and intramolecular charge
transfer. Furthermore,
B2
,
B3
, and the polyurethane
nonlinear optical materials show good optical limiting.
B2
/PU and
B3
/PU not only have excellent nonlinear optical
properties but also have good transmittance, thermal stability, and
processability of polyurethane materials. The combination of pyrenyl
Schiff base derivatives and polyurethane materials greatly improves
the application of nonlinear small molecules in the field of optical
limiting and all-optical switching.
The pyrene derivative (PD) was synthesized with pyrene-1-carboxaldehyde and p-aminoazobenzene by a Schiff base reaction. Then the obtained PD was dispersed in polyurethane (PU) prepolymer to prepare polyurethane/pyrene derivative PU/PD materials with good transmittance. The nonlinear optical (NLO) performances of the PD and PU/PD materials were studied by the Z-scan technique under picosecond and femtosecond laser pulses. The PD has reverse saturable absorption (RSA) properties under the excitation of 532 nm 15 ps pulses, 650 and 800 nm 180 fs pulses, and a low optical limiting (OL) threshold (0.01J/cm2). The PU/PD has a larger RSA coefficient than that of the PD under 532 nm 15 ps pulses. With the enhanced RSA, the PU/PD materials exhibit excellent OL (OL) performance. Good NLO properties, high transparency, and easy processing performances make the PU/PD an excellent choice for use in OL and laser protection fields.
4-phenylethylene derivatives (B1, B2 and B3) with π conjugated systems were designed and synthesized by Sonogashira coupling reaction and Schiff base reaction. Under the ns laser source, the nonlinear absorption coefficients (β) of B2 and B3 are 1.85 × 10−10 m/W and 1.9 × 10−10 m/W. B2 and B3 have good light limit performance. Furthermore, the third harmonic strength of B2 and B3 is 181 and 215 times that of SiO2, respectively. The optical limiting threshold and third harmonic signal show that 4-phenylethylene derivatives will have good application potential in laser protection and frequency conversion.
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