Fabrication of poly(4-vinylpyridine)-b-polystyrene-b-poly(4-vinylpyridine ) triblock copolymer particles via three-dimensional soft confined self-assembly

Using cetyltrimethylammonium bromide (CTAB) as a single surfactant, a series of symmetrical poly(4-vinylpyridine)-b-polystyrene-b-poly(4-vinylpyridine) (VmS24.2kVm) triblock copolymers with various molecular weights m of P4VP blocks (m = 3.0k, 6.3k, 7.9k, 13.4k) were employed to fabricate onion-like particles, spherical particles with an inner curved cylinder, convex lens (CL)-like particles with hexagonal P4VP cylinder and tulip-like particles with alternately stacked PS and P4VP lamella via three-dimensional soft confined self-assembly (3D-SCSA). Both the external shape and internal morphology of VmS24.2kVm particles were closely related to the volume fraction of the P4VP block and the concentration of CTAB. Upon increasing the volume fraction of the P4VP block, the internal phase separation structure of VmS24.2kVm particles changed from a cylinder to a lamella. Interestingly, as the concentration of CTAB increased, VmS24.2kVm particles changed from spherical (or onion-like) particles with a P4VP outmost layer to CL-like or tulip-like particles with a neutral interface, of which PS and P4VP blocks had an analogical preference to the oil/water interface, and finally into spherical particles with a PS outmost layer. The location of P4VP domains in VmS24.2kVm particles was clearly identified by selectively loading Au nanoparticles. It was the first time to observe VSV triblock copolymer particles with a neutral interface via 3D-SCSA using a single surfactant CTAB although it exhibits a preferred affinity and selective interaction with the PS block.