Morphology and dynamics of dense nanometric precursor lms of polymer melts

TL;DR

This study investigates the formation and steady-state behavior of nanometer-thick polymer melt films on silicon wafers, revealing a universal thickness law linked to polymer chain size and highlighting the limitations of existing theories.

Contribution

It demonstrates a universal law for the steady-state thickness of polymer films and models the spreading dynamics considering both polymer-surface and polymer-polymer friction effects.

Findings

Steady-state film thickness equals twice the polymer's gyration radius.

Universal applicability across different polymers and surface conditions.

Existing theories fail to predict the observed thickness law.

Abstract

Nanometer-thick supported lms of polymer melts spontaneously form and spread around sessile droplets that are deposited on oxidized silicon wafers. At steady state, the lms become dense and adopt a uniform thickness which is equal to twice the gyration radius of the free polymer. Remarkably, this law applies to a wide variety of melts and does not depend on the polymer chemistry nor on the surface state (oxide layer thickness, temperature, presence of water adsorbed, etc.). We show that existing theoretical descriptions cannot reproduce this experimental result. Conversely, the evolution toward this equilibrium state witnesses the specicity of the interactions at stake in these conned polymer lms. The chains spreading dynamics can be modeled by taking into account both the polymer/surface friction and the polymer/polymer friction.