A New Family of Dendrimers with Naphthaline Core and Triphenylamine Branching as a Two-Photon Polymerization Initiator

A new family of dendrimers with a naphthaline-core flanked on both sides by triphenylamine-branching was successfully synthesized and presented an increasing two-photon absorption (TPA) cross section from 959 to 9575 GM with the generation number from 1 to 3. These dendrimers can efficiently initiate the acrylate resins to polymerization to obtain very regular diamond structures and display higher two-photon polymerization (TPP) efficiency and sensitivity with the generation number. The overall TPP processes involved in two-photon excitation, intramolecular charge transfer, and intramolecular energy transfer as well as intermolecular electron transfer between initiator and monomer are described. Steady-state fluorescence and time-resolved decay dynamics revealed that the light energy was absorbed by peripheral triphenylamine unit and then transferred to generation 1, the energy funnel. Although strong interaction between dendritic initiator and monomer has been observed based on fluorescence quenching measurements, no intermolecular energy transfer but electron transfer is confirmed by the cyclic voltammograms and HOMO-LUMO measurements. That is, the dendritic initiator first produces the excited state via two-photon absorption, then transfers an electron to an acrylate monomer, and finally induces the later to polymerize.