Phosphorus-containing block copolymer templates can control the size and shape of gold nanostructures

Amphiphilic block copolymers containing phosphine moieties in the main chain are employed as macromolecular ligands for gold (1). The sequential living anionic copolymerization of isoprene (1) and the phosphaalkene, MesP=CPh2 (Mes = 2,4,6-trimethylphenyl) affords the block copolymer [PI](404)-b-[MesP-CPh2](32) (1a). The incorporation of gold(I) moieties into this functional copolymer is accomplished by treating 1 with THT center dot AuCl (THT = tetrahydrothiophene) which affords [PI](404)-b-[MesP(AuCl)-CPh2](32) (2a). Remarkably, dissolution of gold-functionalized 2 in n-heptane, a block-selective solvent for isoprene, affords spherical micelles with gold(l)-rich cores. Micelles were examined by transmission electron microscopy (TEM) and dynamic light scattering (DLS). We also prepared two additional copolymers with longer phosphine blocks and shorter PI segments: [PI](222)-b-(MesP(AuCl)-CPh2](77) (2b) and [PI](164)-b-[MesP(AuCl)-CPh2)(85) (2c). When assembled in isoprene-selective solvents, 2b forms wormlike structures and 2c, with the longest phosphine block, forms fascinating micron sized intertwined wormlike structures. This represents a new method to control the shape and size of gold(I) nanostructures.