The Effect of Femtosecond Laser Irradiation and Plasmon Field on the Degree of Conversion of a UDMA-TEGDMA Copolymer Nanocomposite Doped with Gold Nanorods

Abstract

In this work, the effects of femtosecond laser irradiation and doping with plasmonic gold nanorods on the degree of conversion (DC) of a urethane dimethacrylate (UDMA)–triethylene glycol dimethacrylate (TEGDMA) nanocomposite were investigated. The UDMA-TEGDMA photopolymer was prepared in a 3:1 weight ratio and doped with dodecanethiol- (DDT) capped gold nanorods of 25 × 75 or 25 × 85 nm nominal diameter and length. It was found that the presence of the gold nanorods alone (without direct plasmonic excitation) can increase the DC of the photopolymer by 6–15%. This increase was found to be similar to what could be achieved with a control heat treatment of 30 min at 180 °C. It was also shown that femtosecond laser impulses (795 nm, 5 mJ pulse energy, 50 fs pulse length, 2.83 Jcm−2 fluence), applied after the photopolymerization under a standard dental curing lamp, can cause a 2–7% increase in the DC of undoped samples, even after thermal pre-treatment. The best DC values (12–15% increase) were obtained with combined nanorod doping and subsequent laser irradiation close to the plasmon resonance peak of the nanorods (760–800 nm), which proves that the excited plasmon field can directly facilitate double bond breakage (without thermoplasmonic effects due to the short pulse length) and increase the crosslink density independently from the initial photopolymerization process.

Plasmonic Effect of Gold-Patchy Silica Nanoparticles on Green Light-Photopolymerizable Dental Resin

“…A perfectly matched layer (PML) with 700 nm diameter was also placed around the arrangement. The refractive index of the polymer matrix was set to be 1.53, based on our previous measurements with ellipsometry [ 19 ]. The resulting extinction spectrum has a definite LSPR peak around 532 nm ( Figure 8 c), which corresponds well with the experimentally measured data (see Figure 3 ).…”

“…The measured DC showed the polymerization degree of the crosslinked polymer network after 532 nm irradiation. Pre-photopolymerized samples were analyzed [ 19 , 20 ] with the DSC measurements, which provided information about post-polymerization of unreacted monomers, and pendant vinyl groups and chains. The exothermic event of the first heating cycle of pre-polymerized samples indicated post-polymerization, as a highly cross-linked network was formed.…”

Kinetic model of resonant nanoantennas in polymer for laser induced fusion

“…As the copolymer is transparent the light absorption is minimal, while the refractive index is n = 1.53. The absorption coefficient of the bare polymer matrix at this wavelength would be ≈0.3 cm −1 while doped with gold nanorods it would reach 18 cm −1 [18].…”

“…Now we extend these studies to nanorod antennas embedded into the UDMA-TEGDMA copolymer. Here we consider the refractive index of UDMA-TEGDMA (n = 1.53) [18], which slows down the propagation of light. The short laser pulse is chosen to have a length needed to propagate across the target of 7 • 3 μm = 21 μm thickness.…”

“…In order to prepare such a layered target, the ignition fuel (e.g., deuterium, D, tritium, T, or other nuclei for fusion) are embedded into a hard thin polymer material of seven, 3 μm thick layers. These polymers are Urethane Dimethacrylate (UDMA) and Triethylene glycol dimethacrylate (TEGDMA) in (3:1) mass ratio [17,18]. The UDMA-TEGDMA copolymer molecule contains 470 nuclei, 38 of them are Hydrogen.…”