Role of Nanoparticle Selectivity in the Symmetry Breaking of Cylindrically Confined Block Copolymers

We have comprehensively studied the effect of nanoparticle selectivity on the self-assembly of symmetrical block copolymer (BCP) under cylindrical confinement using simulation and experiment. For the simulation, a coarse-grained molecular dynamics (CGMD) simulation has been utilized, and we investigated the confined assembly using nanoparticles with three different interactions with block copolymer: (i) neutral to both A (wall-attractive) and B (wall-repulsive) phases, (ii) B domain selective, and (iii) A domain selective. It is predicted that nonselective (neutral) nanoparticles (NPs) tend to be placed near the interface between radially alternating layers of A or B domains, while selective (A or B) NPs swell the corresponding phase, inducing discrete asymmetrical morphologies. We also find that pure asymmetrical BCP forms more radially perforated morphologies, while symmetrical BCP/NP forms more discrete morphologies. Experimentally, we have incorporated gold or magnetite NPs with the matching three types of selectivity toward symmetrical diblock PS-b-PI and electrospun them. The morphologies observed from our study have been quantified by morphological classification numbers to identify the degree of asymmetry formed. The qualitative and quantitative comparisons between experiment and simulation confirm the validity of the simulation tool and shed light on the NP’s role on breaking the symmetry of BCP under cylindrical confinement.