Controlled Synthesis of Gold Nanoparticles Incarcerated in Syndiotactic Polystyrene Matrix

CONTROLLED SYNTHESIS OF GOLD NANOPARTICLES INCARCERATED IN SYNDIOTACTIC POLYSTYRENE MATRIX Antonio Buonerba,a Cinzia Cuomo,a Sheila Ortega Sánchez,a Patrizia Canton,b Alfonso Grassi.a a Dipartimento di Chimica, Università degli Studi di Salerno. b Dipartimento di Chimica Fisica, Università Ca’ Foscari di Venezia. abuonerba@unisa.it 1. Introduction Gold Nanoparticles (AuNPs) of controlled dimension (<10 nm) and with narrow dimensional distribution have found application in alcohols oxidation using oxygen as oxidizing agent under very mild conditions.1 To prevent the coalescence, the AuNPs need to be protected e.g. by dispersion in polymer matrices. Here we report on the controlled synthesis of AuNPs using the multiblock copolymer syndiotactic polystyrene-co-cis-1,4-polybutadiene (sPSB) and the use of this catalyst in 1-phenylethanol oxidation. 2. Results and Discussion sPSB samples having different styrene molar fractions (xS = 0.61 - 0.93) were synthesized by copolymerization of styrene and 1,3-butadiene catalyzed by CpTi(MBMP)Cl [MBMP = 2,2’-methylenebis(6-tert-butyl-4-methylphenoxo)].2 The treatment of THF solutions of the sPSBs and of gold compounds [HAuCl4 or AuCl(PPh3)] with NaBHEt3 (B/Au molar ratio = 4) yielded AuNPs incarcerated in the sPSB matrix which were isolated by precipitation with appropriate solvents. The X-ray Debye-Scherrer method and TEM analysis suggest for the AuNPs a size of 1-7 nm at variance of the synthetic route employed. The aromatic polymer matrix strongly stabilize the AuNPs: actually no leaching as well as no dimensional variation were observed even after treatment with neat chloroform or in mixture of this solvent with water (1:1v/v) for 4 days at room temperature. Oxidation of 1-phenyl ethanol to acetophenone readily proceeds in good yields (75% in 24h) at room temperature using air or oxygen at atmospheric pressure. The catalyst was repeatedly used several times without loss of catalytic activity. 3. References [1] Hutchings, G. J. Chem. Commun. 2008, 1148-1164. [2] Cuomo, C. Serra, M. C. Gonzalez Maupoey, M. Grassi, A. Macromolecules. 2007, 40, 7089-7097.