Synthetic advances of internally nanostructured polymer particles: From and beyond block copolymer

External field induced defect transformation in circular confined Gay-Berne liquid crystals

Normally, defects in two-dimensional, circular, confined liquid crystals can be classified into four types based on the position of singularities formed by liquid crystal molecules, i.e., the singularities located inside the circle, at the boundary, outside the circle, and outside the circle at infinity. However, it is considered difficult for small aspect ratio liquid crystals to generate all these four types of defects. In this study, we use molecular dynamics simulation to investigate the defect formed in Gay-Berne, ellipsoidal liquid crystals, with small aspect ratios confined in a circular cavity. As expected, we only find two types of defects (inside the circle and at the boundary) in circular, confined, Gay-Berne ellipsoids under static conditions at various densities, aspect ratios, and interactions between the wall and liquid crystals. However, when introducing an external field to the system, four types of defects can be observed. With increasing the strength of the external field, the singularities in the circular, confined system change from the inside to the boundary and the outside, and the farthest position that the singularities can reach depends on the strength of the external field. We further introduce an alternating, triangular wave, external field to the system to check if we can observe the transformation of different defects within an oscillating period. We find that the position of the singularities greatly depends on the oscillating intensity and oscillating period. By changing the oscillating intensity and oscillating period of the external field, the defect types can be adjusted, and the transformation between different defects can be easily observed. This provides a feasible way to modulate liquid crystal defects and investigate the transformation between different defects.

Recent advances in mixing-induced nanoprecipitation: from creating complex nanostructures to emerging applications beyond biomedicine

Mixing-induced nanoprecipitation (MINP) is an efficient, controllable, scalable, versatile, and cost-effective technique for the preparation of nanoparticles. In addition to the formulation of drugs, MINP has attracted tremendous interest in other fields. In this review, we highlight recent advances in the preparation of nanoparticles with complex nanostructures via MINP and their emerging applications beyond biomedicine. First, the mechanisms of nanoprecipitation and four mixing approaches for MINP are briefly discussed. Next, three strategies for the preparation of nanoparticles with complex nanostructures including sequential nanoprecipitation, controlling phase separation, and incorporating inorganic nanoparticles, are summarized. Then, emerging applications including the engineering of catalytic nanomaterials, environmentally friendly photovoltaic inks, colloidal surfactants for the preparation of Pickering emulsions, and green templates for the synthesis of nanomaterials, are reviewed. Furthermore, we discuss the structure-function relationships to gain more insight into design principles for the development of functional nanoparticles via MINP. Finally, the remaining issues and future applications are discussed. This review will stimulate the development of nanoparticles with complex nanostructures and their broader applications beyond biomedicine.

Formation and Transformation of Polystyrene-block-poly(2-vinylpyridine) Hexasomes in the Solvent Exchange

The generation of inverse micellar nanostructures, especially those with open channels, using commercially available diblock copolymers (BCP), is vital for their wide applications in drug delivery and catalyst templating. However, the rigid requirements for forming inverse morphologies, such as the highly asymmetric molecular structures, the semicrystalline motifs, and concentrated solutions of diblock copolymers, represent obstacles to the development of successful strategies. In this study, the inverse polystyrene-block-poly(2-vinylpyridine) (PS_30K-b-P2VP_8.5K) micelles, i.e., the hexasomes with p6mm lattice, were generated through a modified solvent exchange via adding d-tartaric acid (d-TA) in the nonsolvent. Various intermediate morphologies have been identified with the change of d-TA concentration. Interestingly, in the high d-TA concentration (∼20 mg/mL), the hexasomes with close-packed hoops changed to mesoporous spheres with regularly packed perpendicular cylindrical channels (V_D-TA: V_BCP 6:100), and further to the mesoporous spheres with gyri-like open pores (V_D-TA: V_BCP > 15:100) with the increasing acidity in the mixed solvent. This study presents a simple and economical pathway for fabricating PS_30K-b-P2VP_8.5K hexasomes and first demonstrates these hexasomes can be modified to the morphology with open channels that will benefit their further applications.