Highly efficient two-photon initiated polymerization in solvent by using a novel two-photonchromophore and co-initiators

Abstract

Highly efficient two-photon initiated polymerization in solvent was carried out in a three-component system, which consisted of a novel D-π-A-π-D type chromophore (1 or 2, respectively), the co-initiator, 2, 6-diisopropyl-N,N-dimethylaniline (DDA) and diphenyliodoinum salt, Ph₂I⁺PF₆⁻(PIP). We measured the quasi two-photon polymerization rates (R_p) based on scanning speed and the width of the written protruding line. Polymerization rates of the chromophore 1 and 2 were found to be 113 µm³ s⁻¹ and 157 µm³ s⁻¹ in the case of the laser power 4.5 mW at 820 nm (pulse width: 85 fs, repetition rate 82 MHz ) respectively. In order to estimate the mechanism of the photochemical reaction, the change of UV absorption of the three-component system, T–T transient absorption and the cyclic voltammetry (CV) of the novel chromophores were measured. Correlated with the CV, we interpreted that highly efficient electron transfer between DDA and the chromophore contributed to the long-lived radical cations of the chromophore. As a result, the generation of both DDA radicals and phenyl radicals was ascribed to high sensitivity in TPIP.