Improving the mechanical, spectroscopic and laser ablation characteristics of UDMA-MMA copolymers using a titanocene photoinitiator

Abstract

We have shown that the Irgacure 784 titanocene photoinitiator can be advantageously used to improve the light absorption, mechanical and nanosecond-regime laser ablation properties of urethane dimethacrylate (UDMA)-methyl methacrylate (MMA) polymer blends with photopolymerization using curing with green (520–525 nm) light. The hardness was found to be significantly higher (0.25–0.29 GPa) than that of other UDMA polymer blends photopolymerized using other initiator systems. The established 48–63 % degree of conversion is also comparable to that of similar other blends and is useful in many applications. The laser ablation and laser-induced breakdown spectroscopy (LIBS) properties of these polymers were studied at 266 and 532 nm laser wavelengths. The polymers showed consistently good laser ablation characteristics (reproducible, well-defined, shallow craters) at 266 nm wavelength, whereas at 532 nm, extensive carbonization and strong photothermal effects were observed. LIBS spectra of the blend shows lines of C, H, O, N and Ti as well as C₂ and CN bands, but provide many spectral windows for interference-free analytical measurements. Our findings indicate that UDMA-MMA polymer blends can be good candidates as target matrices for laser ablation-based measurements in the UV or Vis range, in applications like analytical spectroscopy or laser-initiated fusion research.