Silver Nanoparticles Formation Within Unsaturated Polyester/Styrene Resins Induced by UV Irradiation and Thermal Treatment Antonio M. Brito-Silva, 1 Cid B. de Arau ´ jo, 2 Fa ´ bio A. Brayner, 3 Sergio S. Santos, 3 Andre ´ Galembeck, 4,5 Edwin R.C. Milet 5 1 Programa de Po ´ s-graduac ¸a ˜ o em Cie ˆ ncia de Materiais, Centro de Cie ˆ ncias Exatas e da Natureza—Universidade Federal de Pernambuco, Recife, Pernambuco, Brazil 2 Departamento de Fı´sica, Universidade Federal de Pernambuco, Recife, Pernambuco, Brazil 3 Departamento de Biologia Celular e Ultraestrutura, Centro de Pesquisas Aggeu Magalha ˜ es, Fiocruz, Recife, Pernambuco, Brazil 4 Departamento de Quı´mica Fundamental, Universidade Federal de Pernambuco, Recife, Pernambuco, Brazil 5 Laborato ´ rio Multiusua ´ rio de Nanotecnologia, Centro de Tecnologias Estrate ´ gicas do Nordeste—CETENE, Recife, Pernambuco, Brazil This article describes the formation of silver nanopar- ticles (NPs) within preformed unsaturated polyester/ styrene resins in which the resulting color could be tuned by changing the silver load, time, and method used to grow the NPs. NP size and aggregation are responsible for the resulting sample color, and the samples present very good optical transparency. The silver ions were first added to the prepolymer that was crosslinked by free radical polymerization in the absence of light. NP formation was subsequently induced by submitting the transparent and colorless samples to heat or UV irradiation. Within the heated samples, isolated spherical particles ranging from 3 to 40 nm were observed. UV irradiation led to the forma- tion of particle aggregates; however, as the exposure time was increased, silver NPs became well dispersed within the matrix within a particle diameter range of 9 to 24 nm. The particle formation is faster when induced by UV irradiation. Samples were also pre- pared by first dissolving rhodamine 6G in the resin. The emission bandwidth of samples prepared in this way showed a dependence on the silver particles amount and size. POLYM. ENG. SCI., 50:2350–2355, 2010. ª 2010 Society of Plastics Engineers INTRODUCTION The development of new methods for synthesizing sil- ver/polymer nanostructured materials in which the silver nanoparticle (NP) shape and primary particle size distribu- tion, as well as their aggregation, can be controlled is of great interest because of the resulting optical [1, 2], elec- tronic [3, 4], and mechanical [5, 6] properties. Since the polymer host plays a key role in the resulting materials, one must consider its ability to affect Ag þ reduction, to keep the NPs stable, and to provide a good supporting medium that provides both chemical and mechanical stability. The use of thermosets as the supporting media for silver/ polymer nanocomposites was barely explored. However, ther- mosets present significant advantages over thermoplastic poly- mers: (i) molded bulk pieces as well as films can be obtained with high shape stability and (ii) chemical, thermal, and me- chanical properties are usually superior to those of thermo- plastics. In addition, the choice of an appropriate monomer or prepolymer will produce materials that do not require the elimination of solvent or other volatile compounds. The majority of the synthetic approaches to achieve Ag/ polymer nanocomposites described in the literature deal with soluble polymers such as poly(vinyl alcohol) or poly(vinyl- pyrrolidone) that are attractive because they are good parti- cle-stabilizing agents in aqueous solutions and can be easily cast into films [1, 7, 8]. Films formed by solvent evaporation were also reported for poly(aryl esters) [9], poly(amic acid) Correspondence to: Andre ´ Galembeck; e-mail: andre@ufpe.br Contract grant sponsor: Instituto Nacional de C&T de Foto ˆnica/CNPq and and PROCAD/CAPES. DOI 10.1002/pen.21771 Published online in Wiley Online Library (wileyonlinelibrary.com). V V C 2010 Society of Plastics Engineers POLYMER ENGINEERING AND SCIENCE—-2010