title: Templated self-assembly of block copolymers and morphology transformation driven by the Rayleigh instability.
abstract: In the current study, we investigate the self-assembly of polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) confined in the nanopores of the anodic aluminum oxide (AAO) template and the subsequent morphology transformation induced by the Rayleigh instability. PS-b-P4VP nanotubes and nanorods with various internal nanostructures are fabricated by wetting the AAO template with PS-b-P4VP/chloroform solution, and then followed by solvent evaporation. After the removal of AAO template by potassium hydroxide solution, several different solvents (chloroform, toluene, and N,N-dimethylformamide) with different qualities are used to swell and anneal those nanotubes and nanorods suspended in aqueous media. Morphology transformation from nanostructured PS-b-P4VP nanotubes or nanorods to ordered nanospheres is observed by annealing upon chloroform and toluene while the morphology remains unchanged upon N,N-dimethylformamide annealing, indicating that solvent quality is a key factor in tuning the morphology and internal structures. Kinetics study and theoretical analysis for the morphology transition from two-dimensional (2D) block copolymer (BCP) nanotubes and nanorods to three-dimensional (3D) BCP nanospheres are further performed. From the morphological evolution and the quantitative calculation, it is confirmed that this transition is induced by the Rayleigh instability. This study provides a simple but promising method, that is, solvent annealing method, for the fabrication of BCP nanospheres with ordered internal nanostructures, which may have great application in drug delivery and other nanotechnology.
authors.affiliation: State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences , Changchun 130022, People's Republic of China.
authors.forename: Nan
authors.initials: N
authors.lastname: Yan
authors.forename: Yuping
authors.initials: Y
authors.lastname: Sheng
authors.forename: Hongxia
authors.initials: H
authors.lastname: Liu
authors.forename: Yutian
authors.initials: Y
authors.lastname: Zhu
authors.forename: Wei
authors.initials: W
authors.lastname: Jiang