Deposition Patterns Induced by the Evaporation of the Cyclic Diblock Copolymer Solution Droplet

In this work, molecular dynamics simulations are performed to study the deposition patterns of the cyclic diblock copolymer solution nanodroplet on the solid surface (the wall). We focus on how the nonbonded interaction strength influences the deposition pattern and the evaporation process. The interaction strength includes the interaction between the wall and polymer blocks (epsilon AW and epsilon BW), interaction between the solvent and wall (epsilon SW), and interaction between polymer blocks (epsilon AB). Conditions of the formation of various structures, such as multilayer and coffee-ring structures, are systematically studied. Diblock copolymers can generate ordered structures with multiple domains of polymer blocks. A detailed analysis indicates that the coffee-ring structure results from the shrinkage of interfaces, the heterogeneity of the solution, and the self-assembly of polymer loops. In addition, it is found that the evaporation flux of the droplet periphery is lower than that of the central area on the lyophilic wall. In the nanoscale droplet, the solute accumulation at the periphery retards the diffusion of solvents from entering the vapor phase and thus cannot be neglectable as in the macroscale model. This work helps to build up a guideline for the design of deposition patterns of the cyclic diblock copolymer solution nanodroplet, which paves the way for the application of the cyclic diblock copolymer to inkjet printing.