Shape control of nanostructured cone-shaped particles by tuning the blend morphology of A-b-B diblock copolymers and C-type copolymers within emulsion droplets

Abstract

Block copolymers (BCPs) under colloidal confinement can provide an effective route to produce non-spherical particles. However, the resulting structures are typically limited to spheroids, and it remains challenging to achieve a higher level of control in the particle shape with different symmetries. Herein, we exploit the blend of BCPs and statistical copolymers (sCPs) within emulsion droplets to develop a series of particles with different symmetries (i.e. Janus-sphere and cone-shaped particles). The particle shape is tunable by controlling the phase behavior of the polymer blend consisting of a poly(styrene-block-1,4-butadiene) (PS-b-PB) BCP and a poly(methylmethacrylate-statistical-(4-acryloylbenzophenone)) (P(MMA-stat-4ABP)) sCP. A key strategy for controlling the phase separation of the polymer blend is to systematically tune the incompatibility between the BCP and sCP by varying the composition of the sCPs (ϕ_4ABP, mole fraction of 4ABP). As a result, a sequential morphological transition from a prolate ellipsoid, to a Janus-sphere, to a cone-shaped particle is observed with the increase of ϕ_4ABP. We further demonstrate that the shape-anisotropy of cone-shaped particles can be tailored by controlling the particle size and the Janusity, which is supported by quantitative calculation of the particle shape-anisotropy from the theoretical model. Also, the importance of the shape control of the cone-shaped particles with high uniformity in a batch is demonstrated by investigating their coating properties, in which the deposited coating pattern is a strong function of the shape-anisotropy of the particles.