Rapid Solidification of Plant Latices from Campanula glomerata Driven by a Sudden Decrease in Hydrostatic Pressure

TL;DR

Campanula glomerata plant latex solidifies rapidly due to a sudden pressure drop, which triggers coagulation and phase separation.

Contribution

The paper introduces a novel mechanism of latex solidification driven by hydrostatic pressure changes and liquid–liquid phase separation.

Findings

Campanula glomerata latex solidifies faster than Euphorbia characias and technical latices.

Rapid solidification is caused by a pressure drop triggering serum influx and phase transition.

Cryo-SEM and QCM-D data support the role of liquid–liquid phase separation in solidification.

Abstract

By monitoring the solidification of droplets of plant latices with a fast quartz crystal microbalance with dissipation monitoring (QCM-D), droplets from Campanula glomerata were found to solidify much faster than droplets from Euphorbia characias and also faster than droplets from all technical latices tested. A similar conclusion was drawn from optical videos, where the plants were injured and the milky fluid was stretched (sometimes forming fibers) after the cut. Rapid solidification cannot be explained with physical drying because physical drying is transport-limited and therefore is inherently slow. It can, however, be explained with coagulation being triggered by a sudden decrease in hydrostatic pressure. A mechanism based on a pressure drop is corroborated by optical videos of both plants being injured under water. While the liquid exuded by E. characias keeps streaming away, the liquid exuded by C. glomerata quickly forms a plug even under water. Presumably, the pressure drop causes an influx of serum into the laticifers. The serum, in turn, triggers a transition from a liquid–liquid phase separated state (an LLPS state) of a resin and hardener to a single-phase state. QCM measurements, optical videos, and cryo-SEM images suggest that LLPS plays a role in the solidification of C. glomerata.

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