Phase Behavior Of AB Diblock Copolymers In Different Three-dimensional Confined Spaces

Scientists refer to a class of substances consisting of macromolecules or groups,such as liquid crystals,polymers,colloids,membranes,foams,particulate matter,and living matter,as soft substances or complex fluids,and block copolymers are typical soft materials.Due to its rich self-assembly behavior and its importance in many fields of technology,block copolymer systems have become one of the most important areas of interest in the cross-research field of condensed matter physics and chemistry.Considering the bulk phase morphology of the block copolymer and the interaction parameters between the blocks and the volume fraction of different segments of the block copolymer,the SCFT is used to calculate the bulk of the block copolymer under unconstrained conditions.Phase behavior.By solving the surface shape equation of Helfrich surface elastic theory evolution,a three-dimensional space symmetry blank vesicle is constructed as a three-dimensional constrained space.The reduced volume is defined by the relationship between the volume and surface area of differently shaped vesicles.Four different types of reduced vesicles,namely sphere,prolate,oblate and stomatocyte,are selected as three-dimensional constrained spaces.By performing regular volume changes on these four typical confined spaces,a three-dimensional constrained space model with different restricted volumes and different reduced volumes can be obtained.In this paper,the phase behavior of the columnar phase AB asymmetric block copolymer in a three-dimensional constrained space with a restricted wall being neutral is studied.The results show that the phase behavior of the AB block copolymer is significantly different from that of the bulk column phase in the three-dimensional space.The trend of the phase structure and the degree of limitation of the columnar phase AB block copolymer under sphere confinement is basically consistent with the previous research results.The phase morphology evolves from a single droplet structure to a plurality of symmetric droplet structures.To the center is a spherical structure and a droplet-like structure dispersed around it.The columnar phase AB block copolymer is more severely frustrated by the prolate,the symmetry of the phase structure is destroyed,and the regularity of the phase structure is not strong.Under the confinement of the oblate,the phase behavior of the columnar phase AB block copolymer exhibits more severe frustration and orientation limitations,and the symmetry of the copolymer phase morphology is destroyed.The phase morphology change of the columnar phase AB block copolymer under the non-central symmetry stomatocyte is somewhat similar to the spherical constraint,and the phase structure has a distinct dispersion distribution.Under these four spatial constraints,the free energy of the columnar phase AB block copolymer decreases with the increase of the confined space;at the same space limited scale,as the reduced volume decreases,the block The free energy of the copolymer is gradually increased.The different surfaces obtained by solving the Helfrich shape equation can be further extended to other three-dimensional closed surfaces with non-axis symmetry.Therefore,the method can construct a limited space of various forms,so that the phase behavior of the block copolymer in different morphological nano-constrained environments can be studied.At the same time,the phase behavior of block copolymers with more complex topologies in confined spaces can be further extended.The theoretical research of this thesis can provide a new idea for experimentally obtaining nano-constrained spaces with different phase structures and different forms and different degrees of frustration,and also enrich the theory of the phase behavior of copolymers in confined spaces.