Electric-field-induced Self-assembly Of Diblock Copolymers And Phase Separation Of Homopolymers In Confined Space

Under the external conditions,the block copolymers can self-assemble into longrange ordered phase structures.These long-range ordered nanostructures have obvious potential applications in miniaturization of modern electronic devices.In this paper,the self-consistent field method and molecular dynamics method are applied to investigate the self-assembly of AB diblock copolymers under electric field,and the self-consistent field method is adopted to study the phase separation of two homopolymers in confined space.The computer simulation can reduce the time of experiment exploration and provide guideline for relevant experimental research.The explicit contents of this thesis include:1.The phase diagram of diblock copolymers in unconfined space under electric field was studied with molecular dynamics method.The results show that with the increase of the electric field intensity,the kinds of the ordered phase structures in phase diagram were gradually reduced.The ordered phase structures in the phase diagram under strong electric field are lamellar phase,cylindrical phase and the spherical phase.Then additional free ions are added to the diblock copolymer melt system and this new system is placed between parallel restricted plates.Besides electric field strength,the effect of alternating current and ionization was also considered in diblock copolymers selfassembly.Furthermore,the radius of gyration of a diblock polymer is calculated in NVT ensemble and in NPT ensemble with various electric filed strength.2.We applied self-consistent field theory to study the self-assembly of a diblock copolymer confined between two parallel neutral substrates on which a set of electrodes was imposed to form a patterned electric field.The results showed that an alternatively distributed electric field can induce the formation of a parallel lamellar phase structure,which exists stably only in the system with selective substrates.The phase structure was proved to be sensitive to the characteristics of the electric field distribution,such as the strength of the electric field,the size and position of the electrodes,and the corresponding phase diagram was calculated in detail.The transition pathway of the phase structure from the perpendicular layered phase to the parallel-layered phase was further analysed using the minimum energy path method.It is shown that the path and the active energy barrier of the phase transition depend on the electric field strength.Compound electric field patterns that can be designed to control the formation of novel and complex microphase structures were also examined.3.The influence of cylindrical confined space on the phase separation of two kinds of homopolymers was studied by self-consistent field theory.By changing the cylindrical radius,the height of the cylinder and the size of the confined space,it is found that the width of the U-shaped binodal curve narrows and the whole curve moves upwards.Oppositely,the U-shaped spinodal curve widens and moves downwards.The transition pathway of the phase structure from the uniformly mixed phase structure to the two phases separation structure was shown using the minimum energy path method.