Theoretical Study On The Conformational Transition Of Polymer Brush Grafted Diblock Copolymer Chains

Stimulus-responsive polymers can produce strong conformational or chemical reactions to change in environmental temperature,p H,and electric field.These polymer materials have a wide range of applications in the fields of biomedicine and materials engineering,such as the design of smart surfaces.Polymer brushes are considered a very promising material for designing stimulus-responsive surfaces.Therefore,this article takes the polymer brush as the research object,and calculates the relevant parameters through self-consistent field theory.Investigates the conformational changes of the ends of the diblock copolymer single chain grafted on the polymer brushes and the conformational changes of the connection points.In the specific research,firstly,the self-consistent field theory was used to calculate the density distribution function of the single chain of the copolymer,and the change of the adsorption strength was further combined to obtain the function change of the average height and the probability distribution function during the transition.Secondly,on this basis,the influence of the length of the active block and the inert block of the diblock copolymer on the phase transition point,phase transition width and phase transition barrier are discussed.Focus on the analysis of the effect of polydispersity on the conformational changes at the end of the copolymer chain.And the influence of the length of the inert block of the copolymer chain under the monodisperse brush on the conformational change at the connection point when the length is long enough.The research results are intended to provide possible theoretical clues for in-depth exploration of the design of switch sensors based on polymer brushes.The dissertation is divided into four parts,the main contents are as follows:Chapter 1: Introduction.This chapter mainly gives an introduction to the introduction of polymer brushes,the classification of polymer brushes,and the development and application of polymer brushes.Furthermore,review and summarize the development process and research status of polymer brushes in three aspects: experiment,theory and simulation.Finally,explanation the main research about this paper.Chapter 2: The conformational changes of the chain ends of grafted diblock copolymers in monodisperse and polydisperse polymer brushes.The theoretical models and calculation methods of grafted block chains under brush with different dispersive polymers are introduced.The average height of free ends is used to measure the size of copolymer single chains,and the probability distribution of block chain ends during adsorption transitions is discussed.On this basis,the focus is on comparing the phase diagrams of the monodisperse brush and the polydisperse brush to obtain the space occupied by the first-order phase transition and the continuous phase transition.The effects of polydispersity on the phase transition point,phase transition width and phase transition barrier are investigated,and the significance of polydispersity for the design of switching sensors is further analyzed.Chapter 3: The conformational changes of the connection points of grafted diblock copolymer chains in monodisperse brushes.In this chapter,a theoretical model based on monodisperse polymer brushes is constructed.By changing the length of the active block and inert block of the diblock copolymer chain,it focuses on the analysis of increasing the length of the inert block when the length of the active block is longer.The influence of time on the phase transition point,phase transition width and phase transition barrier.It is further analyzed when the inert block is long enough,which is beneficial to design a more efficient and fast switching sensor.Chapter 4: Summary.Several important conclusions are given in the design of efficient and fast switching sensors.In addition,some shortcomings of this study are summarized,and the development prospects of related fields are prospected briefly.