Dissipative Particle Dynamics Study Of Multicompartment Micelles

Amphiphilic block copolymers can self-assemble into micelles in a selective solvent. Recently, multicompartment micelles have received great attention, which are composed of a water-soluble shell and a microphase-segregated hydrophobic core. Due to their novel morphologies and interesting structures, multicompartment micelles may find potential applications in drug delivery and nanotechnology. In this work, computer simulation is applied to study the self-assembly of mixed micelles from block copolymer blends in solution. The main results obtained are:(1) Dissipative particle dynamics simulations are performed on multicompartment micelles formed by blending star and linear triblock copolymers, in which the influence of blending ratio is discussed. The simulation confirms that the blending ratio is an important influencing factor on the morphology of mixed micelles. A slight change in the blending ratio can produce various mixed micelles with new morphologies and structures.(2) The dynamic processes of the formation of novel mixed multicompartment micelles are traced at the molecular level. The results demonstrate that different blending options lead to different formation pathways of mixed micelles and different time scale to reach the equilibration of the self-assembly system. Two possible evolution mechanisms of a multicompartment micelle with a ring/cogwheel core are identified, large cylindrical micelle curling then closing up and disc-like micelle perforation. The initial mixing state may have little effects on the final morphology; however, the fine structure can be affected to some extent.(3) The effects of block sequence, block ratio, block length as well as chain architecture on mixed multicompartment micelles are investigated systematically, and the knowledge of the morphology and structure control of micelle are obtained. The DPD simulation results show that blending of copolymers is an effective way to control the morphology and inner structure of multicompartment micelles, and block sequence, block ratio, chain architecture and block length all have large effects. By changing these parameters, different domain arrangement, mixed degree, relative distance, degree of participation and extensibility of two triblock copolymers in hydrophobic core can be tuned, and diverse morphologies of mixed micelles with alterable domain arrangements and overall size can be obtained.(4) Diffusion dynamics of star and linear polymer blends in dilute solution is studied. The dynamic processes are elucidated at the molecular level by tracing the trajectories of different kinds of copolymer chains. When mixed micelles are formed from the cooperative self-assembly of copolymer blends, the diffusivities of star and linear triblock copolymer chains are influenced greatly upon changing block ratio, block length and molecular weights, leading to evolution control in multicompartment micelles formation. By changing these factors, the diffusivity differences between star and linear copolymers can be tuned, and thus influence the formation of mixed or pure aggregates and the fraction of two kinds of copolymers incorporated in one aggregate; the relative diffusivities of star and linear triblock copolymers can be tuned due to their different molecular weight dependency.