Synthesis and incorporation of dodecanethiol capped silver nanoparticles into poly(styrene-b-isoprene-b-styrene) block copolymer and their influence in the morphology

The aim of this study was to incorporate dodecanethiol capped silver nanoparticles (Ag-DT) into poly(styrene-b-isoprene-b-styrene) (SIS) block copolymer and investigate their dispersion and their influence in the resultant surface morphology. The silver nanoparticles were prepared by reduction of silver salts employing sodium borohydride (NaBH4). Different amount of dodecanethiol surfactant were employed in the synthesis in order to obtain nanoparticles with homogeneous distribution and controlled size. The silver nanoparticles functionalized with dodecanethiol were analyzed by proton nuclear magnetic resonance (1H NMR) and Fourier transformed infrared (FTIR) spectroscopy. The achieved silver nanoparticles size distribution was analyzed by transmission electron microscopy (TEM) and UV–vis techniques. Taking into account the obtained results, nanoparticles synthesized with the lowest amount of surfactant were selected. Dodecanethiol grafting density into silver nanoparticles was calculated by using thermogravimetric analysis (TGA). Nanoparticles were incorporated into the block copolymer in different proportions (0.1, 1.0 and 2.0 wt%). Energy dispersive X-ray (EDX) measurements were done parallel to TEM images to verify the composition of nanoparticles. TEM analysis showed that the incorporation of surfactant capped Ag nanoparticles into the SIS matrix has great influence on how the block copolymer is nanostructured. The positioning of nanoparticles in the interface influences the resulting copolymer morphology. Thus, increasing nanoparticles amount, block copolymer changed from hexagonally close-packed morphology to a mixture of hexagonally close-packed and cubic close-packed morphologies.