Dispersion of Gold Nanoparticles in UV-Cured, Thiol-Ene Films by Precomplexation of Gold-Thiol

J. Paige Phillips Buchanan, University of Southern Mississippi
Nicole M. Mackey, University of Southern Mississippi
Bridget S. Confait, University of Southern Mississippi
David T. Heaps, University of Southern Mississippi

Abstract

Alkyl thiols and alkenes (enes) polymerize via an extremely rapid step-growth, free-radical chain process, uninhibited by air, to give high-density networks with excellent mechanical and physical properties. These thiol-ene coatings are potentially useful for a wide variety of coatings, adhesives, and optical applications. In this work, a series of nanogold-containing UV-cured, thiol-ene coatings were prepared from trimethylol propane tris(3-mercaptopropionate) (trithiol) and pentaerythritol ally ether (triene) monomers using a unique procedure which facilitates precomplexation of the gold-thiol prior to photocuring. Irgacure 651 (1 wt %) was used as a photoinitiator, and nano-old was incorporated at 0-1 wt %, average similar to 10 nm size particles by TEM. Physical and mechanical properties were characterized using bulk tack analysis and other standard techniques: DSC, TGA, pencil hardness, and gel fractions. In general, films were found to be low absorbing, in the visible range and highly uniform and to contain well-dispersed nanogold particles. Although the rate of polymerization was modestly retarded by the presence of gold nanoparticles, functional group conversions (C=C and S-H) and gel fractions were high. Increasing nanogold content resulted in an, increase in T-g measured by DSC (-15 to -8 degrees C for 0-1 wt % nanogold, respectively) due to the increasing number of physical gold-thiol cross-links created. TGA analysis revealed a small negative impact of increasing nanogold composition on relative thermal stability. The 1 wt % nanogold-containing samples possessed appreciable electrostatic discharge (ESD) character, with ESD times of 1-10 s measured using a commercial charge plate analyzer.