The block copolymer of poly(styrene)-block-poly(tert-butyl acrylate) (PSt-b-PtBA) has been synthesized by an atom transfer radical polymerization (ATRP) method. Then the amphiphilic block copolymer of poly(styrene)-block-poly(acrylic acid) (PS-b-PAA) was obtained by hydrolysis from PSt-b-PtBA copolymers in HCl solution. Furthermore, the architectures of the copolymers were confirmed by FT-IR and 1H NMR spectra. GPC analysis was used to estimate the molecular weight and the molecular weight distribution of the copolymers. Three amphiphilic copolymers with different molecular weights formed micelles in an ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]). The nanostructures of the PSt-b-PAA micelles formed in the ionic liquid were observed by TEM (transmission electron microscopy) and DLS (dynamic light scattering). The self-assembled morphologies of the copolymers are strongly dependent on the length of PAA block chains when the chain length of PSt is fixed. With the increase of molecular weight of PAA in the diblock copolymers, some spherical micelles were obtained. With further decrease of the PAA molecular weight in the copolymers, the spherical morphology was turned to peanut.

Key words: atom transfer radical polymerization, amphiphilic block copolymer, ionic liquid, self-assembly