Conjugated Polymer Nanoparticles as Visible Light Panchromatic Photoinitiators for 3D Printing of Acrylic Hydrogels

Abstract

Conjugated polymers (CPs) are known to generate radical reactive oxygen species (ROS) such as hydrogen peroxide through photoinduced charge transfer processes involving water. In this work, this ability to generate radicals is utilized here to use conducting polymer nanoparticles (CPNs) as photoinitiator systems (PIS) for the polymerization of acrylic monomers in aqueous media. The CPNs do not require co-initiators and also act as cross-linkers. CPNs with different light-absorption properties effectively initiate photopolymerization across the entire visible light spectrum, reaching high monomer conversion yields (60-99%) under blue, green, or red LED exposure. The resulting hydrogels demonstrate remarkable characteristics, including a significant water absorption swelling capacity (900-1600%) and substantial gel formation percentages (70-97%). Notably, the CPNs are evenly dispersed within the hydrogel matrix after photopolymerization, maintaining their photophysical properties and their ability to generate reactive species, potentially rendering the hydrogel suitable for bacterial photodynamic inactivation. Furthermore, PIS CPNs enable 3D printing with a fine resolution of up to 100 μm using a digital light processing technique.