Study on the Self-assembly Behavior of Polycaprolactone Star-Shaped Copolymers Based on Dissipative Particle Dynamics

In this study, the pH-responsive self-assembly behavior of polycaprolactone star-shaped block copolymers in aqueous solution was systematically investigated by dissipative particle dynamics. The changes in morphology during the self-assembly process were studied by adjusting the number of polymer star arms, the degree of ionization of the terminal carboxylic acid group, and the concentration of the polymer in the solution. The results show that during the self-assembly process, the star-shaped copolymers undergo a series of structural transformations from spherical micelles to worm-like micelles and then to lamellar micelles as ionization and solution concentration change. When the degree of ionization is high, the electrostatic repulsion is enhanced, resulting in the formation of smaller spherical micelles; in contrast, when the degree of ionization is low, the electrostatic repulsion is weakened, resulting in the formation of larger and more complex worm-like or lamellar structures. With an increase in the number of arms, the self-assembly behavior of the system gradually transitions from complex morphologies (such as lamellar micelles and branched worm-like micelles) to simple morphologies (such as linear worm-like micelles and spherical micelles). This study provides important theoretical references and practical guidance for revealing the regulatory mechanisms of carboxyl ionization, the number of polymer star arms, and solution concentration on the self-assembly behavior of amphiphilic block copolymers.