Effect of Selective Solvent Addition Rate on the Pathways for Spontaneous Vesicle Formation of ABA Amphiphilic Triblock Copolymers

Abstract

In this study, the kinetics of vesicle formation of ABA amphiphilic triblock copolymers from an initially homogeneous state was theoretically and experimentally investigated by adding a selective solvent into the system. The pathway of spontaneous vesicle formation depended greatly on the selective solvent addition rate. At a slow addition rate, the pathway followed three stages: (1) the amphiphilic triblock copolymer combined into a large irregular aggregation; (2) the large irregular aggregation broke into big irregular spheres; and (3) some hydrophilic molecules in the big irregular spheres diffused toward the surface, and some hydrophilic molecules diffused toward the center, forming vesicles. However, at a fast addition rate, the pathway was as follows: (1) the amphiphilic triblock copolymer aggregated into many small spheres; (2) the small spheres merged to form rod-like micelles first and then oblate membranes; and (3) the oblate membranes closed up to form vesicles. This pathway difference for vesicle formation can be attributed to the existence of many metastable states in the system. This finding not only provides new insight into the origins of vesicles but also provides further understanding on the self-assembly kinetics of amphiphilic block copolymers in a selective solvent.

Solubilization of saikosaponin a by ginsenoside Ro biosurfactant in aqueous solution: Mesoscopic simulation

“…This caused the end-to-end distance to increase again. This formation process is similar to that of amphiphilic triblock copolymers, as has been verified in previous studies [32][33][34]. It also explains the changes in core structure indicated in the MesoDyn simulation.…”

Janus-like spheres, disks, rings, cylinders, and vesicles from the self-assembly of mixture of AB and BC diblock copolymers in A- and C-selective solvents

“…MC simulation has proven to be an efficient method to study the solution-state self-assembly of copolymers, which include AB diblock copolymers, 24 ABA, 25,26 and ABC triblock copolymers, 27-30 ABC miktoarm star terpolymers, 31,32 and tetrablock copolymers. 33 All simulations were carried out in a simple cubic lattice with a volume of V ¼ L Â L Â L, where L ¼ 40.…”

Concentration dependent pathways in spontaneous self-assembly of unilamellar vesicles

“…1,2,8 Most well studied systems are surfactants 6,7,[10][11][12][14][15][16] and block copolymers [17][18][19] in selective solvents. The self-assembly process can be induced by rapid mixing of oppositely charged surfactant solutions, 6,10,15,20 temperature 19,21,22 or pH jumps. 23,24 The process of formation of ULVs usually involves different stages with certain rate limiting steps, making the kinetics spanning from milliseconds to days, depending on the type of amphiphiles employed and the type of transformation taking place.…”