Studies On The Phase Behavior Of Star Triblock Copolymer Micelles And Block Copolymer Nanocomposite Based On Self-consistent Field Theory

First,we extend the self-consistent field theory(SCFT) to investigate self-assembled morphologies of amphiphilic ABC star triblock copolymers consisting of hydrophilic A blocks and hydrophobic B and C blocks and the blends with their counterpart linear AB diblock copolymers in solution.Compared to the most simple block copolymer-linear diblock copolymers which normally self-assemble in solution into spheres,cylinders and vesicles shape micelles,such as star triblock copolymers with complex topological structures can form abundant structures.Specifically,the most distinct type is the multicompartment micells originated from two immiscible hydrophobic parts of triblock copolymers,for example,hamburger micelles,segmented wormlike micelles, bead-on-string wormlike micelles and raspberry micelles.Furthermore,the aggregated morphology of ABC star triblock copolymers is strongly influenced by the addition of linear AB diblock copolymers.The most significant feature is that the long segmented worms will become shorter,to form hamburger micelles with the addition of AB diblock copolymers.Moreover,we find a new toroid micells in which the core of micelles is composed of star triblock copolymer and the diblock copolymers are distributed at the two ends of axes of the aggregates.Then,we study the phase behavior of block copolymer nanocomposite with the SCFT.It is known that the properties of material can be increased a lot by hybriding only a little amount of nanoparticles.Moreover,the properties of material are strongly influenced by its morphologies.Therefore,in order to obtain the best mechanical properties,morphologies need to be exactly controlled.Due to the introduction of nanoparticles,the phase behavior of block copolymers may become more complex as many new factors such as the shape,size,quantity of particles and particle-polymer interactions,etc.will be considered.In this paper,we use a hybrid SCFT to deal with the self-assembly of block copolymers in the presence of spherical nanoparticles.For the symmetric chain length of diblock copolymers,we find that the neutral particles tend to distribute at the interface of the lamellar phase.With the increase of the numbers of neutral nanoparticles,the lamellar phase will be disordered and even transformed to the hexagonal cylinder phase.If the nanoparticles affine to one of the blocks,they tend to be distributed in the middle of that phase.Furthermore,the increase of the quantity of nanoparticles with affinity leads to the lamellar phase changed to the hexagonal cylinder phase.At last,we simulate the evaporation process of diblock copolymer thin film. Because the solvent is evacuated in producing polymer film,the solvent evaporation process strongly affects the final structure and properties.Experiments show that the long-range ordered structure can be obtained by careful control of the rate of evaporation. Here we use the dynamic density functional theory which proposed by Fraaije and combined the simple model of evaporation process of Buxton et al to simulate the phase behavior and dynamics of block copolymer thin film during the solvent evaporation.This simple model only considers the interaction between different components and the key factor,i.e.,solvent evaporation rate.The results show that perpendicular lamellar phase can be easily formed under suitable evaporation rate for the case of block copolymers with symmetric composition.