Capillary-induced phase separation in ultrathin jets of rigid-chain polymer solutions
A. V. Subbotin+*, A. N. Semenov×
+Topchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences, 119991 Moscow, Russia
*Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, 119071 Moscow, Russia
×Institut Charles Sadron, CNRS-UPR 22, Universite de Strasbourg, 23 rue du Loess, BP 84047, 67034 Strasbourg Cedex 2, France
Abstract
In the present paper, we study the terminal stage of the capillary
thinning of a polymer solution jet formed with rod-like molecules. On long scales
exceeding the rod length a uniform jet gets unstable according to the classical
Plateau-Rayleigh pinching mechanism. We show, however, that a qualitatively
different faster process, which can prevent the jet from breaking-up, generically
comes into play once the jet radius becomes smaller than the rod length. Namely the
solvent drains out onto the jet surface forming annular droplets there, while the
rods stay trapped inside the jet polymer core. As a result, the jet core becomes
more concentrated and can solidify eventually. This process can provide a universal
mechanism of the capillary-induced solvent/polymer phase separation leading to fiber
formation (fiber spinning) from rod-like polymer solution jets.