Microstructure evolution of block copolymer blends and composites in confined geometries

Abstract

Block copolymers consist of two or three chemically different polymer chains connected by covalent bonds. The incompatibility between polymer chains induces well-organized phase separated domains like lamella, cylinder and sphere domains which are applicable to nanoscale patterns in nano-electronics, biological assays, and high-density storage at above order-disorder transition (ODT). Recently, block copolymer self-assembly in two-dimensional confined geometry has been studied extensively due to the secondary possibility to control the directional order of self-assembled domains but the three-dimensional confinement effect has never been studied so far. In this thesis, fabrication of polystyrene-block-polybutadiene diblock copolymer (PS-b-PB) particles and the investigation of block copolymer self-assembly in a spherical confined geometry were mainly discussed. Block copolymer self-assembly in a confined geometry is strongly dependent on the ratio of the diameter (D) of the particle to the feature spacing $(L_0)$ of the phase-separated periodic domains of block copolymers and the surface preference as well as the product of the Flory-Huggins parameter (χ) and the degree of polymerization (N) and the volumetric ratio of one component (f). f was varied by the addition of polystyrene homopolymers (hPS) and microphase transition was observed for hPS which have much lower molecular weight than that of PS chains of PS-b-PB as previously reported for thin film of block copolymer. The effect of $D/L_0$ ratio was studied by observing various sized particles which were generated by emulsion-based method using homogenizer and unique morphologies such as helices and hoops were observed inside particles, which are described in chapter 2. The surface property was controlled by the mixing ratio of two amphiphilic diblock copolymer surfactants which have selective affinity with each block of PS-b-PB and the effect of surface preference on the self-assembly of PS-b-PB in partic...