Monte Carlo Simulation Of The Self-assembly Behavior Of Polydisperse Diblock Copolymer In Selective Solvent

Monte Carlo simulation was used to study the effect of molecular weight distribution and composition distribution on the self-assembly behavior of diblock copolymers.Self-avoiding chains was carried out in a simple cubic lattice system with 40*40*40 sites,the periodic boundary condition was applied in all simulations.The following results were obtained:Firstly,the effect of the polydispersity of hydrophobic blocks was investigated.In this system,the length of the hydrophilic blocks A is faxed at 2,whereas three length-different hydrophilic blocks,i.e.L_B1 = 2 L_B2 = 6 and L_B3 = 10 were employed respectively.The polydisperse diblock copolymer system was constructed by mixing the three chains in length, i.e.,A₂B₂,A₂B₆,A₂B₁₀ and keeps the number average molecular weight as a constant.The polydisperse index(I_PDI) of the system ranges from 1.0 to 1.4 in this study.With an increase in I_PDI,the simulation results indicate that the micelle morphologies are transformed from vesicles to bilayers and finally to spheres.Secondly,effect of the polydispersity of the chains was investigated.In this system,the composition ratio of A and B block is R = 1:3,and it contains three length-different subcomponents which areL₁=4,L₂=8 and L₃=12.The polydisperse diblock copolymer system was constructed by mixing these three chains and keeps the number average molecular weight as a constant.The polydisperse index(I_PDI) of the system ranges from 1.0 to 1.2 in this study.With an increase in I_PDI,the simulation results indicate that the micelle morphologies transformed from vesicles to spheres.