Pis’ma v ZhETF, vol. 111, iss. 1, pp. 50 - 51

January 10

Capillary-induced phase separation in ultrathin jets of rigid-chain

polymer solutions

A. V. Subbotin+∗1), 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

Submitted 23 October 2019

Resubmitted 20 November 2019

Accepted 21

November 2019

DOI: 10.31857/S0370274X20010105

Capillary thinning and break-up of liquid jets is one

We examined two qualitatively different mechanisms

of the long-standing important problems attracting wide

of polymer liquid jet instability arisen on long and short

scientific and industrial interest [1]. The problem is par-

length-scales. For length-scales exceeding the rod length

ticularly challenging in the case of polymer liquids [2-4].

the surface tension-driven thinning develops in a con-

Last decades the essential progress has been attained in

ventional way (Plateau-Rayleigh mechanism [1]) which

study of Newtonian jets [5, 6]. However experiments re-

ultimately should result in breaking up of the jet. By

veal that Newtonian and polymer liquid threads show

contrast, we show that at shorter length-scales the rods

qualitatively different types of behavior [7]. In partic-

get effectively trapped inside the jet core whereas the

ular the jets formed by solutions of flexible polymers

solvent drains to the surface and forms annular droplets

can show formation of blistering patterns where solvent

there, Fig. 1. The latter process of capillary phase sepa-

droplets set on micro- or nano-fibers [8-10]. The na-

ture of these patterns is insufficiently explored. One of

the approaches elucidating this phenomenon was based

on the opportunity for polymer molecules to migrate in

the thinner regions due to the stress-concentration cou-

pling effect [11]. Another molecular model, which has

been proposed recently, puts forward the idea of a flow

Fig. 1. (Color online) Illustration of annular droplet of sol-

induced phase separation in dilute polymer solutions

vent on the polymer solution jet

under extension [12, 13]. It predicts a polymer/solvent

demixing due to the flow-induced orientation of poly-

ration occurs much faster and can prevent the jet from

mer chains acting to reverse their effective interactions

breaking up. This mechanism works both with non-

from repulsive to attractive. As a result the elongated

volatile solvents and with no specific attraction between

chains tend to micro-separate and form a network of

oriented polymer chains and differs from the mechanism

fibrils tending to compress laterally by squeezing the

of phase separation which is connected with a reduction

solvent out to the jet surface.

of the steric repulsion of the stretched chains [12, 13].

Most of the above results cover solutions of flexi-

Moreover, the described mechanism may be also at work

ble chains. Meanwhile solutions of stiff polymers such

in solutions of semiflexible polymers if the chains are

as polypeptides, DNA, cellulose, aromatic polyamide

highly stretched due to extension. Thereby the discov-

copolymers etc. are particularly interesting for applica-

ered capillary-driven phase separation effect can provide

tions. Our study is focused on capillary thinning of so-

a universal mechanism of fiber formation in solutions of

lutions of rigid rods in the regime of ultrathin jet when

stretched polymers.

its diameter is smaller than the rod length and the rods

Experimental observation and identification of the

are highly oriented along the jet axis. Such regime arises

predicted solvent/polymer demixing mechanism is a

at the terminal stage of capillary thinning.

challenging problem. A thin quasi-uniform jet can be

easily produced, for example, by stretching a liquid

¹⁾e-mail: subbotin@ips.ac.ru

droplet. One option is to use solutions of DNA. These

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2020

Capillary-induced phase separation in ultrathin jets. . .

chains can be very long and form nano-thick fibers in

6. Y. Li and J. E. Sprittles, J. Fluid Mech. 797, 29 (2016).

solutions [14]. The most appropriate system to verify

7. A. V. Bazilevskii, S. I. Voronkov, V. M. Entov, and

our results must involve very long rods. Such macro-

A. N. Rozhkov, Sov. Phys. Dokl. 26, 333 (1981).

molecular rods (with length ≥ 1-10 microns) are known,

8. R. Sattler, S. Gier, J. Eggers, and C. Wagner, Phys.

examples are given by protein polymers (F-actin, mi-

Fluids 24, 023101 (2012).

crotubules) and other self-assembling supramolecular

9. A. V. Semakov, I. Yu. Skvortsov, V. G. Kulichikhin, and

structures (like tri-arylamine fibers) [15-19].

A. Ya. Malkin, JETP Lett. 101, 690 (2015).

A. V. Subbotin acknowledges financial support from

10. A. Ya. Malkin, A. V. Semakov, I. Yu. Skvortsov, P. Za-

tonskikh, V. G. Kulichikhin, A. V. Subbotin, and

the Russian Science Foundation (Grant # 17-79-30108).

A. N. Semenov, Macromolecules 50, 8231 (2017).

A. N. Semenov acknowledges a partial support from the

11. J. Eggers, Phys. Fluids 26, 033106 (2014).

International Research Training Group (IRTG) “Soft

12. A. V. Subbotin and A. N. Semenov, J. Polym. Sci.: Part

Matter Science: Concepts for the Design of Functional

B: Phys. Ed. 54, 1066 (2016).

Materials”.

13. A. N. Semenov and A. V. Subbotin, J. Polym. Sci.: Part

Full text of the paper is published in JETP Letters

B: Phys. Ed. 55, 623 (2017).

journal. DOI: 10.1134/S0021364020010051

14. X. Fang and D. H. Reneker, J. Macromol. Sci.: Part B:

Phys. 36, 169 (1997).

15. F. Gittes, B. Mickey, J. Nettleton, and J. Howard, J. Cell

1. J. Eggers and E. Villermaux, Rep. Prog. Phys. 71,

Biol. 120, 923 (1993).

036601 (2008).

16. F. Oosawa and S. Asakura, Thermodynamics of the

2. G. H. McKinley, Visco-elasto-capillary thinning and

Polymerization of Protein, Acad. Press, San Diego

break-up of complex fluids, in Rheological Review (The

(1975).

British Society of Rheology, Aberystwyth, 2005), p. 1.

17. J. van Mameren, K. C. Vermeulen, F. Gittes, and

3. A. Ya. Malkin, A. Arinstein, and V. G. Kulichikhin,

C. F. Schmidt, J. Phys. Chem. B 113, 3837 (2009).

Prog. Polym. Sci. 39, 959 (2014).

18. E. Moulin, F. Niess, M. Maaloum, E. Buhler, I. Nyrkova,

4. V. G. Kulichikhin, I. Yu. Skvortsov, A. V. Subbotin,

and N. Giuseppone, Angew. Chem. Int. Ed. 49, 6974

S. V. Kotomin, and A. Ya. Malkin, Polymers 10, 856

(2010).

(2018).

19. I. Nyrkova, E. Moulin, J. J. Armao IV, M. Maaloum,

5. J. R. Castrejón-Pita, A. A. Castrejón-Pita, S. S. Thete,

B. Heinrich, M. Rawiso, F. Niess, J.-J. Cid, N. Jouault,

K. Sambath, I. M. Hutchings, J. Hinch, J. R. Lister, and

E. Buhler, A. N. Semenov, and N. Giuseppone, ACS

O. A. Basaran, PNAS 112, 4582 (2015).

Nano 8, 10111 (2014).

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