Alkyl/Cycloketonic Modulations in Photoinitiator Molecular Engineering for Efficient Multiphoton Polymerization

Abstract

Dibenzylidene ketone (DBK) photoinitiators (PIs) hold promise for one-photon polymerization (OPP) and two-photon lithography (TPL), owing to easily synthesized extended π-conjugated frameworks via one-step aldol condensation. However, industrial adoption is limited by poor solubility and critical OPP reactivity/TPL processability mismatch. Herein, we report a dual-parameter molecular engineering strategy for tert-butylcarbazole-functionalized DBK PIs, tuning N-alkyl chains (methyl, ethyl, n-butyl, n-dodecyl) and cyclic ketone spacers (C5: cyclopentanone; C6: cyclohexanone) to optimize polymerization properties. For OPP, C5-DBKs exhibit enhanced visible photosensitivity, enabling rapid kinetics under 405–520 nm LEDs; N-dodecyl derivatives show excellent photobleaching and deep curing. For TPL, C5-DBKs have superior two-photon absorption (σ_TPA) but C6-DBKs offer better solubility (1 wt% in PETA) and act as efficient one-component TPL PIs. Using a 780 nm fs laser, N1C6/PETA enables high-precision fabrication: threshold matrix writing exhibits wide processing window and good uniformity, achieving sub-200 nm resolution (167 nm linewidth at 45 mW, 50 mm·s^–1) and high-fidelity microlens arrays. Complex 3D microstructures (intricate logos, sub-micron text, Chinese jade belt bridge, nanoscale-pore photonic crystals) demonstrate versatility in photonics, metamaterials and micro-pattern anti-counterfeiting. This work establishes OPP/TPL structure-activity relationships (SARs) and a versatile molecular design platform for industrial coatings and micro/nano-manufacturing.

Keywords

Dibenzylidene ketone / Carbazole / Photoinitiator / Photopolymerization / Photobleaching / Two-photon lithography / Nano-manufacturing / Structure-activity relationship

RIGHTS & PERMISSIONS

2026 SIOC, CAS, Shanghai, & WILEY-VCH GmbH