Tetracyanobutadienyl-based Nonlinear Optical Dendronized Hyperbranched Polymer Synthesized via Facile [2+2] Cycloaddition Polymer Postfunctionalization

Highly Efficient and Stable Binary Cross-Linkable/ Self-Assembled Organic Nonlinear Optical Molecular Glasses

The development of electro-optical materials with high chromophore loading levels that possess ultrahigh electro-optic coefficients and high long term alignment stability is a challenging topic. Anthracene-maleimide Diels-Alder (DA) reaction and π-π interaction of Anthracene-pentafluorobenzene and benzene-pentafluorobenzene are developed for making highly efficient binary cross-linkable/self-assembled dendritic chromophores FZL1-FZL4. A covalently or non-covalently cross-linked network is formed by DA reaction or π-π interaction after electric field poling orientation, which greatly improves the long-term alignment stability of the materials. An electro-optic coefficient up to 266 pm V-1 and glass transition temperature as high as 178 °C are achieved in cross-linked film FZL1/FZL2, and 272-308 pm V-1 is achieved for self-assembled films FZL1/FZL4 and FZL3/FZL4 due to high chromophore density (3.09-4.02 × 1020 molecules cm-3 ). Long-term alignment stability tests show that after heating at 85 °C for over 500 h, 99.73% of the initial r33 value is maintained for poled crosslinked electro-optic films 1:1 FZL1/FZL2. The poled self-assembled electro-optic films 1:1 FZL1/FZL4 and 1:1 FZL3/FZL4 can still maintain more than 97.11% and 98.23%, respectively, of the original electro-optic coefficient after being placed at room temperature for 500 h. The excellent electro-optic coefficient and stability of the material indicate the practical application prospects of organic electro-optic materials.

Electro-optic crosslinkable chromophores with ultrahigh electro-optic coefficients and long-term stability

The development of organic electro-optic materials with ultrahigh electro-optic coefficients and high long-term alignment stability is the most challenging topic in this field. Next-generation crosslinkable nonlinear optical chromophore molecular glasses were developed to address this problem. A highly stable EO system including crosslinkable binary chromophores QLD1 and QLD2 or crosslinkable single chromophore QLD3 and multichromophore QLD4 with large hyperpolarizability was synthesized using tetrahydroquinoline as the donor. When the temperature continues to rise after poling, the chromophores modified with anthracene and acrylate can undergo Diels-Alder crosslinking reaction to fix the oriented chromophores through chemical bonds. After crosslinking, the QLD1/QLD2 and QLD2/QLD4 films achieved very high maximum r ₃₃ values of 327 and 373 pm V^-1, respectively, which are the highest values reported for crosslinkable chromophore systems. After Diels-Alder cycloaddition, the glass transition temperature of the EO film increased by ∼90 °C to 185 °C, which is higher than for any other pure chromophore films. After being annealed at 85 °C, 99.63% of the initial r ₃₃ value could be maintained for over 500 h. The ultrahigh electro-optic activity and high long-term alignment stability of these materials showed new breakthroughs in organic EO materials for practical device explorations.

Nonlinear Optical Properties of Pyrene Derivatives Based on a Donor-Acceptor Structure and Its Polyurethane Composites

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.