Aqueous dynamic molecular and particular assembly of amphiphilic block copolymer visualized by in-situ LP-TEM

Abstract

The self-assembly structure of a general amphiphilic block copolymer is carried out by direct dissolution into a selective solvent or through the gradual exchange from common solvents to selective solvent for one block. In this process, the self-assembled structure was either dynamically equilibrated in a solvent to have the lowest free energy or kinetically trapped to exhibit a uniform morphology. In the case of kinetically trapped assemblies, morphological reconstruction and dynamic deformation occurred, implying the possible Brownian motion-based particle growth by collision and fusion. The self-assembly accompanying the dynamic nanoscale process of these organic molecules has not been directly observed, and basic mechanisms such as fusion, fragmentation, and growth are still subject to much research. The block copolymer self-assembly used in this study is a crew-cut micelle, not a star-shape micelle, and it can be confirmed that the volume fraction due to the ratio of the block length is controlled and the self-assembly structure transitions. Here, using the amphiphilic block copolymer, the self-assembly behavior of nanoparticles in real-time according to the molecular weight of the block in an aqueous solution was to be observed using a transmission electron microscope(TEM) and the dynamic behavior of the nanostructure was quantitatively analyzed by multiple object tracking analysis. This study provides a useful strategy for observing mechanisms of amphiphilic block copolymer self-assembly and the growth behavior of organic molecules based on Brownian motion.