Shaping Block Copolymer Microparticles by Positively Charged Polymeric Nanoparticles

Abstract

Shape-transforming block copolymer (BCP) microparticles have attracted extensive attention due to their promising applications in nanotechnology, biomedicines, interfacial science, and other fields. As their performance is highly associated to their shape and structure, it is very important to realize the precise control of particle shape. In this report, a method is proposed to regulate the shape and structure of polystyrene-b-polydimethoxysiloxane (PS-b-PDMS) microparticles by using positively charged core-crosslinked nanoparticles (CNPs) as a cosurfactant, combining with cationic surfactant cetyltrimethylammonium bromide (CTAB). The electrostatic repulsive interactions between CNPs and CTAB dominate the shape of PS-b-PDMS particles. Upon introducing NaCl, the electrostatic repulsion is reduced, resulting in the reshape of PS-b-PDMS particles from striped Janus ellipsoids to onion-like microspheres at a critical concentration of NaCl (c NaCl ). Interestingly, it is found that the critical c NaCl first increases then reaches a plateau, with the increase in the crosslinking degree of the CNPs. The work provides a simple strategy to tailor the morphology of BCPs by manipulating the electrostatic interaction.

Dynamic Electrostatic Interfacial Engineering for Block Copolymer Microparticles with Reversible Structures

“…When chloroform in the oil phase volatilizes, the emulsion droplets shrink, ultimately resulting in the solidification and microphase segregation of PS-b-PDMS within a confined space. 11,12 The NPSs adsorbed on the interface direct the rearrangement of PS-b-PDMS chains. Since the NPSs have PS-NH 2 tails, they can create a selective interface highly affiliative to the PS block of PS-b-PDMS.…”

“…Another key feature of the emulsion stabilized by NPSs is that the elastic film of NPSs at the oil/water interface affords a deformable space to direct the confined assembly of BCPs inside the droplets. When chloroform in the oil phase volatilizes, the emulsion droplets shrink, ultimately resulting in the solidification and microphase segregation of PS- b -PDMS within a confined space. , The NPSs adsorbed on the interface direct the rearrangement of PS- b -PDMS chains. Since the NPSs have PS-NH 2 tails, they can create a selective interface highly affiliative to the PS block of PS- b -PDMS .…”

“…Notably, the internal structure of PS- b -PDMS microparticles can be reversibly switched over multiple solvent annealing cycles (Figure S14). The NPSs can dynamically and reversibly regulate both the interfacial interactions and the internal structure of BCP microparticles, which is not feasible with traditional surfactants or nanoparticles. ,− , …”

“…The NPSs can dynamically and reversibly regulate both the interfacial interactions and the internal structure of BCP microparticles, which is not feasible with traditional surfactants or nanoparticles. 6,[8][9][10][11][12][13][14]18 The influence of the molecular weight (MW) and weight fraction (φ) of PS-NH 2 on the dynamic interfacial electrostatic assembly was revealed. As shown in Figure 3a, a clear boundary can be found with the increase of MW.…”

“…The interfacial interaction between incompatible components is critical for manufacturing functional nanomaterials with designable structures and high performance, which plays a decisive role in areas such as Pickering emulsions, fluorescence imaging, and block copolymer (BCP) self-assembly. − In particular, in the emulsion-templated soft confined assembly of BCPs, the soft emulsion interface allows spontaneous deformation by facilely modulating the oil/water interfacial interactions. − Previous reports have shown that the interfacial interaction mainly depends on the interfacial affinity between surfactants and BCPs, which determines the interfacial selectivity of oil/water interface and ultimately the shape and internal nanostructure of the BCP microparticles. − However, surfactants with specific responsive behavior (e.g., light-, pH-, and temperature-responsiveness) often involve complicated chemical synthesis. ,, …”