Double-click synthesis of polysiloxane third-order nonlinear optical polymers with donor–acceptor chromophores

A series of novel polysiloxane compounds possessing third-order non-linear optical properties were synthesized using PMMS (poly[3-mercaptopropylmethylsiloxane]) as the main chain structure. The electron-rich alkyne side chain containing a dialkylamine substituent was grafted to the backbone via a thiol–ene click polymerization followed by a Sonogashira cross-coupling reaction. The donor–acceptor chromophores were inserted into the side chain of the polymer by a [2 + 2] click reaction allowing the molecule to have a broader absorption in the visible and near-infrared regions and a narrower optical band gap. After the click reaction, the polymer undergoes a transition from reverse saturation absorption to saturable absorption (RSA-SA). All polymers displayed good solubility and photophysical properties, and were thermally stable. Z-Scan experiments showed that all compounds possess unique non-linear optical properties.