Polymerization-Induced Self-Assembly of Micelles Observed by Liquid Cell Transmission Electron Microscopy

Abstract

In this paper, we describe the use of liquid cell transmission electron microscopy (LCTEM) for inducing and imaging the formation of spherical micelles from amphiphilic block copolymers. Within the irradiated region of the liquid cell, diblock copolymers were produced which self-assembled, yielding a targeted spherical micellar phase via polymerization-induced self-assembly (PISA). Critically, we demonstrate that nanoparticle formation can be visualized in situ and that in the presence of excess monomer, nanoparticle growth occurs to yield sizes and morphologies consistent with standard PISA conditions. Experiments were enabled by employing automated LCTEM sample preparation and by analyzing LCTEM data with multi-object tracking algorithms designed for the detection of low-contrast materials.

Self-assembling peptides imaged by correlated liquid cell transmission electron microscopy and MALDI-imaging mass spectrometry

“…It has been demonstrated that the electron flux and cumulative electron flux utilized during LCTEM experiments are key parameters to consider and to mitigate beam-induced structural and chemical damage to the materials being imaged, as well as radiolysis of the solvent itself 9,19,20 . Determining the degree of influence of the electron beam to a given system during in situ TEM experiments has largely been limited to observing qualitative changes to a material’s structure 11,21–23 , observing its disintegration 6,16 , or by intentionally growing a nanomaterial directly using electron beam effects 5,7,24–28 . A major source of the difficulty in assigning chemical structures and identities to materials following an LCTEM experiment arises as a result of the small quantity of sample present in the low volumes found within a liquid cell (~<3 pL).…”

Enzyme‐Responsive Polymer Nanoparticles via Ring‐Opening Metathesis Polymerization‐Induced Self‐Assembly

“…Classical amphiphilic polymer assembly via the solvent switch method is often conducted at less than 5 wt% solids, which renders scaleup difficult. [4][5][6][7] In contrast, polymerizationinduced selfassembly (PISA) [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] can pro vide an efficient route to high concentrations of welldefined polymeric nanomaterials. The process works when an initial, soluble polymer is extended, with a second block growing and gradually becoming incompatible with the solvent, leading to the aggregation of polymer chains into defined structures.…”

Characterizing the Core-Shell Architecture of Block Copolymer Nanoparticles with Electron Microscopy: A Multi-Technique Approach

“…Other imaging techniques such as SEM [24] or atomic force microscopy (AFM) [25] have been generally overlooked. Very recently, Gianneschi and coworkers showed the ability of liquid cell TEM to visualize copolymer micelles [26,27] and initiate their formation in situ [28]. The barriers to imaging particle core-shell architecture include small diameters (sometimes well below 100 nm), low differential contrasts, and limited thicknesses of the lyophilic shell.…”