Polymer nano-doplets forming liquid bridges in chemically structured slit pores: A computer simulation

TL;DR

This study uses molecular dynamics simulations to analyze how polymer nanodroplets form liquid bridges in chemically structured slit pores, revealing shape variations, density profiles, and interaction forces at the nanoscale.

Contribution

It introduces a detailed simulation approach to study polymer nanodroplets on chemically patterned surfaces and their bridging behavior in slit pores, advancing understanding of nanoscale wetting phenomena.

Findings

Droplet shape and contact angle vary with droplet radius.

Density profiles across droplets are characterized.

Force measurements reveal droplet merging dynamics.

Abstract

Using a coarse-grained bead-spring model of flexible polymer chains, the structure of a polymeric nanodroplet adsorbed on a chemically decorated flat wall is investigated by means of Molecular Dynamics simulation. We consider sessile drops on a lyophilic (attractive for the monomers) region of circular shape with radius R_D while the remaining part of the substrate is lyophobic. The variation of the droplet shape, including its contact angle, with R_D is studied, and the density profiles across these droplets also are obtained. In addition, the interaction of droplets adsorbed on two walls forming a slit pore with two lyophilic circular regions just opposite of one another is investigated, paying attention to the formation of a liquid bridge between both walls. A central result of our study is the measurement of the force between the two substrate walls at varying wall separation as well as the kinetics of droplet merging. Our results are compared to various phenomenological theories developed for liquid droplets of mesoscopic rather than nanoscopic size.