| Because of the microscopic phase separation characteristics,block polymers are often used to prepare nanoscale microstructures.The diblock polymer contains two chemically incompatible components.When the extent of this repulsion exceeds a certain threshold,the block polymer will undergo obvious phase separation,resulting in repeated microscopic regions with a size of tens of nanometers.This size is in the size range of a single unit in the chip.Although the most advanced semiconductor lithography technology has broken through the resolution below 10 nm,its high cost and low yield still restrict the development of high-end chips.Alternatively,combining the microscopic phase separation behavior of block copolymers with photolithography technology,scientists have already developed the“soft lithography”technology.However,when the unit size goes down to 20 nm,especially below 10 nm,the phase separation of traditional block copolymers is relatively weak,and the interface of the assembled structure is blurred.Therefore,Professor Cheng proposed the concept of“giant surfactants”to solve this technical problem.The giant surfactants have the molecular characteristics of a polar head associated a flexible hydrophobic tail.The head are often hydrophilic molecular nanoparticles with well-defined structural rigidity,such as hydrophilic polyhedral oligomeric silsesquioxane（POSS）,fullerene[60](C60),etc.In the thin film state,the giant surfactant exhibits strong phase separation characteristics below 10 nm,which solves the problems in the traditional diblock copolymer phase separation system.However,in order to further improve the sharpness of the phase interface and the orientation of the phase separation pattern,the interaction parameter between the head and tail components of the giant surfactant needs to be further optimized,and the polar head also needs to have a faster and more sensitive response.Based on the above requirements,this work focuses on the giant surfactant with polyoxometalate（POM）as the head and polystyrene（PS）as the flexible tail,and explores its micro-phase separation behavior in the ultra-thin film state.The innovation of applying this molecule to the soft etching technology lies in:（1）Compared with POSS and C60,there is a stronger incompatibility between POM that are inorganic and organic polymers,so they have larger Flory-Huggins interaction parameter;（2）POM is a type of metal oxide cluster,which has a high etch contrast with carbon-based polymers;（3）POM is a type of charged particles,and thus,the high response efficiency of the applied electric field and magnetic field will help to spatially orient the giant surfactant micro-phase separation structure.Specifically,through the click reaction between Keggin POM and PS,a series of giant surfactants with the same head and different molecular weight tails were prepared.Through temperature annealing,we studied the microphase separation behavior of this series of samples in bulk state by means of small angle X-ray scattering（SAXS）.On the other hand,using spin coating technology,we prepared giant surfactant films of different thicknesses（30-100 nm）and subjected them to solvent evaporation annealing treatment.Finally,the joint test of SAXS and TEM proved that when the molecular weight of PS is between 2K and 11K,the sample self-assembles to form lamllar structure;when the molecular weight of PS is 11K and 12K,the sample self-assembles to form hexagonal cylinder structure. |
