Model Bridging Effects of Asymmetrical Triblock Copolymers

Abstract

AbstractSummary: We have performed Monte Carlo simulations to study the bridging of symmetrical or asymmetrical triblock copolymers confined between two similar or different solid surfaces based on a simple lattice model. The influence of the molecular structure, surface separation, adsorption energy, chain composition, and the chain concentration on the fractions of chains with bridge, loop and dangling configurations are reported in detail. The results show that the largest bridging fraction is given only when symmetrical triblock copolymers are confined between two parallel surfaces with the same adsorption energy. The bridge fraction is decreased so long as the asymmetry of the copolymers or the difference between the two surfaces is enhanced. It was found also that the bridging fraction increases as the adsorption energy increases. The bridging fraction Ωbridge under different separations, Lz, can be expressed as $\Omega _{{\rm bridge}} = A(1 - L_z /L_{z.\max } )^\alpha $ in various situations. On the other hand, by introducing a symmetry index ν, the influence of molecular structure of copolymers on the bridges can be illustrated approximately by a relation $(1 - \Omega _{{\rm b,asym}} /\Omega _{{\rm b,symm}} ) = B(1 - \nu )^\zeta $ when the two surfaces are similar and the adsorption energy is not too high. Combining the two expressions, data of the bridge fractions for copolymers of different symmetries confined between surfaces with different separations can be described with a single equation, which, in some occasion, can be used for prediction.Influence of molecular structure on the bridging fraction for ${\rm A}_{r_{{\rm A1}} } {\rm B}_{{\rm 40}} {\rm A}_{r_{{\rm A2}} }$.imageInfluence of molecular structure on the bridging fraction for ${\rm A}_{r_{{\rm A1}} } {\rm B}_{{\rm 40}} {\rm A}_{r_{{\rm A2}} }$.