D-pi-A-pi-D Initiators Based on Benzophenone Conjugate Extension for Two-Photon Polymerization Additive Manufacturing

A two-photon polymerization initiator is a kind of nonlinear optical material. With the demand for more efficient initiators in two-photon polymerization additive manufacturing, there are more and more related studies. In this paper, four conjugate-extended two-photon polymerization initiators with different alkane chain lengths were designed and synthesized, and single-photon, two-photon, and photodegradation experiments were carried out. Additive manufacturing experiments illustrated that the designed molecules can be used as two-photon initiators, and the writing speed can achieve 100,000 mu m/s at a laser power of 25 mW. Through theoretical calculation and experimental comparison of the properties of molecules with different conjugation degrees, it was proven that a certain degree of conjugation extension can improve the initiation ability of molecules; however, this improvement cannot be extended infinitely. Solubility tests of different acrylates showed that molecules with different alkane chain lengths have varying solubility. Changing the molecular alkane chain length may be favorable to adapt to different monomers.