Online Rheological Investigation on Ion-Induced Micelle Transition for Amphiphilic Polystyrene-<i>block</i>-Poly(acrylic acid) Diblock Copolymer in Dilute Solution

The ion-induced micellar transition is online-investigated by the time dependence of the viscosity of the solution under shear flow for the first time. During the morphological transition, the change in the micellar structure can be tracked by the change in viscosity. Adding HCl or CaCl₂ into pre-prepared spherical micelle solution from the self-assembly of polystyrene-<i>block</i>-poly­(acrylic acid) (PS₁₄₄-<i>b</i>-PAA₂₂) in the <i>N</i>,<i>N</i>-dimethylformamide (DMF)/water mixture, the micellar structures change into short cylinders, long, entangled cylinders, and then lamellae or vesicles, corresponding to the viscosity increasing first and then declining. When HCl or CaCl₂ is added to the pre-prepared spherical micelle solution formed by PS₁₄₄-<i>b</i>-PAA₅₀ in the dioxane/water mixture, the micellar structures are quickly transformed into cylinders or lamellae before carrying out the rheological measurement and then are turned to vesicles or spheres under the shearing, corresponding to a gradual decline in viscosity. This study shows that the rheology can be a very simple and effective online method on the investigation of the micellization, which plays an important role in understanding the micellization mechanism and micellar transition pathway of block copolymers in dilute solution

Growth Mechanism Deconvolution of Self-Limiting Supraparticles Based on Microfluidic System

The synthesis of colloidal supraparticles (SPs) based on self-assembly of nanoscopic objects has attracted much attention in recent years. Here, we demonstrate the formation of self-limiting monodisperse gold SPs with core–shell morphology based on the building blocks of flexible nanoarms in one step. A flow-based microfluidic chip is utilized to slow down the assembly process of the intermediates, which surprisingly allows for observation of ultrathin gold nanoplates as first intermediates. Notably, these intermediate cannot be observed in traditional synthesis due to their rapid rolling-up to form the second-order nanostructure of flexible hollow nanoarms. The growth mechanism of SPs can then be deconvoluted into two seed-mediated steps. Monte Carlo simulations confirm that the self-limiting growth of binary SPs is governed by a balance between electrostatic repulsion and van der Waals attraction