GOLD NANOPARTICLE SYNTHESIS IN GRAFT COPOLYMER MICELLES

An amphiphilic poly(acrylic acid)/polystyrene graft copolymer (PAA-g-P S) has been used to form ''nanoreactors'' for the synthesis of gold cl usters. Such copolymers tend to form stable micelles in non-polar orga nic solvents where the poly(acrylic acid) chains constitute the core, and the polystyrene chains, the shell. In the present study, the micel lar structure of PAA-g-PS in toluene has been demonstrated by dynamic light scattering and transmission electron microscopy (TEM). The subse quent preparation of gold-graft copolymer composites involved the intr oduction of gold chloride (AuCl3), either in powder form or previously dissolved in ether, into the micellar cores of the PAA-g-PS in toluen e. The gold salt was then reduced by ultraviolet (UV) irradiation of t he emulsion, or of dried cast films. TEM and ultraviolet-visible (UV/V is) spectroscopy were used to characterize the resulting composites. G old particles of less than 5 nm in diameter were observed in all cases , but the size distribution and the spatial arrangement of the cluster s in the cast films were modified when diethyl ether was used to intro duce AuCl3 into the PAA-g-PS micellar cores. This was thought to be du e to enhanced nucleation of the gold particles and partial disruption of the micellar cores in the presence of diethyl ether.