Spontaneous Assembly of Miktoarm Stars into Vesicular Interpolyelectrolyte Complexes

Abstract

Mixing a bis-hydrophilic, cationic miktoarm star polymer with a linear polyanion leads to the formation of unilamellar polymersomes, which consist of an interpolyelectrolyte complex (IPEC) wall sandwiched between poly(ethylene oxide) brushes. The experimental finding of this rare IPEC morphology is rationalized theoretically: the star architecture forces the assembly into a vesicular shape due to the high entropic penalty for stretching of the insoluble arms in non-planar morphologies. The transmission electron microscopy of vitrified samples (cryogenic TEM) is compared with the samples at ambient conditions (in situ TEM), giving one of the first TEM reports on soft matter in its pristine environment.

In-situ liquid phase TEM observations of nucleation and growth processes

“…This technique has been applied to a broad range of materials systems, including metallic and semiconductor nanoparticles and nanowires [9,, geochemical and biological minerals [8,10,[40][41][42], electrochemical systems (see Ref. [17] for a recent review), protein complexes [40,43,44], viruses, and self-assembling systems of organic films, vesicles, macromolecules, and nanoparticles [10,29,43,[45][46][47][48]. Moreover, nucleation and growth events can be triggered within LP-TEM liquid cells using a number of methods, including mixing of reagents [41], in-diffusion of a gaseous reactant [10], electrochemical reaction [17,18], heating [49], and through the radiolytic effects of the electron beam [50][51][52].…”

Writing Silica Structures in Liquid with Scanning Transmission Electron Microscopy

“…the interaction of the electron beam with the fluid is a matter of concern as it may induce free electrons in the liquid and also gradients in temperature and pH (due to water decomposition), and beam induced deposition of nanoparticles is also often observed. Indeed, many of the reported experiments so far have either a) used the electron beam to drive the processes under investigation,[10a],[11b] have imaged objects rather than processes, or c) reported on the effects of the electron beam on the events observed. [10b,c],[12b]…”

Dynamics of Soft Nanomaterials Captured by Transmission Electron Microscopy in Liquid Water

“…30 Furthermore, organic liposomes and synthetic polymer vesicles have been imaged via in situ TEM as stationary, static objects and structures. 16,31,32 However, to our knowledge there are no examples using this imaging technique to capture the dynamics or motion of soft organic materials at the nanometer length scale. This constitutes a tremendous gap in our capabilities despite the fact that other techniques including dynamic light scattering (DLS), small-angle neutron scattering (SANS), small-angle X-ray scattering (SAXS) and Nanoparticle Tracking Analysis (NTA) are capable of analyzing size and morphology of nanomaterial populations in solution in real time.…”