Polyelectrolyte-Regulated Block Copolymer Self-Assembled Ordered Structure And Mechanism Research

Based on the ordered nanostructure of block copolymer self-assembly,which has broad application prospects in the field of surface patterning,such as nanolithography,water separation and photonic crystal.How to obtain the vertical orientation structure effectively in the macroscopic range is a key issue for the application of block copolymers in industry.However,block copolymer self-assembly at the interface usually forms parallel orientations which are not conducive to industrial applications.At present,the random copolymer brush which have the same monomer composition as the block copolymer was used to control the nanostructure orientation of the block copolymer.This method requires the substrate has an oxide layer,and it is cumbersome to synthesize the corresponding random copolymer,which is inconvenient for industrial application of the block copolymer.Therefore,it is significant for practical application of block copolymers to develop a convenient and effective controlling way.In this paper,a new regulation method was constructed: the preparation of polyacrylamide hydrochloride(PAH)and polyacrylic acid(PAA)polyelectrolyte multilayer films were used by layer-by-layer self-assembly method to induce nanostructure orientation.Surface energy and surface roughness of the multilayer film were characterized by contact angle and atomic force microscopy(AFM).The experimental results show that the surface energy of the PAH/PAA multilayer film can be effectively controlled by varying the PAH and PAA concentrations.The "fingerprint" morphology of AFM and the out-of-plane diffraction peak of grazing incidence X-ray small angle scattering(GISAXS)confirm that PAH/PAA multilayer film can induce the vertical orientation of PS-b-PMMA self-assembled structure.By using the Scherrer equation to analyze the scattering peak width of GISAXS,the order of the self-assembled structure of PSb-PMMA on polyelectrolyte multilayer films with different concentration ratios is obtained.It was found that polyelectrolyte multilayer films with different concentration ratios could induce the self-assembly morphology of PS-b-PMMA with different ordering,which determined the optimality of PAH/PAA multilayer film in regulating PS-b-PMMA orientation.In addition,the phase behavior of PS-b-PMMA in thermal annealing process was studied by GISAXS in-situ experiment.The experimental results show the vertical orientation of the film in the initial stage of film formation is non-equilibrium due to the volatile of the solvent.As the temperature increases,the volatilization of solvent and the movement of the molecular chain causes the vertical orientation to disappear.In the cooling stage,PS-b-PMMA sets up to appear vertical orientation signals due to the induction of modified layer and the vertical orientation signal became more and more stronger with the decreased of temperature.It indicated that the cooling process was the key to thermally induced the regulation of PS-bPMMA structure orientation.The main work of this thesis is to study the regulation of PAH/PAA multilayer membrane on PS-b-PMMA self-assembly structure by means of AFM and GISAXS,it certainly has positive significance for promoting the industrial application of block copolymers.