Blistering of viscoelastic filaments

TL;DR

This paper investigates the capillary thinning and instability phenomena in viscoelastic polymer filaments, revealing new instabilities and the formation of a permanent solid fiber at nanometer scale.

Contribution

It introduces a novel 'breathing' instability and detailed linear instability analysis, advancing understanding of filament breakup and solid fiber formation.

Findings

Identification of a new 'breathing' instability.

Observation of filament separation into a solid phase.

Formation of a permanent nanometer-thick polymer fiber.

Abstract

When a dilute polymer solution experiences capillary thinning, it forms an almost uniformly cylindrical thread, which we study experimentally. In the last stages of thinning, when polymers have become fully stretched, the filament becomes prone to instabilities, of which we describe two: A novel "breathing" instability, originating from the edge of the filament, and a sinusoidal instability in the interior, which ultimately gives rise to a "blistering" pattern of beads on the filament. We describe the linear instability with a spatial resolution of 80 nm in the disturbance amplitude. For sufficiently high polymer concentrations, the filament eventually separates out into a "solid" phase of entangled polymers, connected by fluid beads. A solid polymer fiber of about 100 nanometer thickness remains, which is essentially permanent.