Irreversible Shear-Activated Gelation of a Liquid Crystalline Polyelectrolyte

We report irreversible, shear-activated gelation in liquid crystalline solutions of a rigid polyelectrolyte that forms rodlike assemblies (rods) in salt-free solution. At rest, the liquid crystalline solutions are kinetically stable against gelation and exhibit low viscosities. Under steady shear at...

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Bibliographic Details
Published in:ACS macro letters 2020-07, Vol.9 (7), p.957-963
Main Authors: Fox, Ryan J, Hegde, Maruti, Zanelotti, Curt J, Kumbhar, Amar S, Samulski, Edward T, Madsen, Louis A, Picken, Stephen J, Dingemans, Theo J
Format: Article
Language:English
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Summary:We report irreversible, shear-activated gelation in liquid crystalline solutions of a rigid polyelectrolyte that forms rodlike assemblies (rods) in salt-free solution. At rest, the liquid crystalline solutions are kinetically stable against gelation and exhibit low viscosities. Under steady shear at, or above, a critical shear rate, a physically cross-linked, nematic gel network forms due to linear growth and branching of the rods. Above a critical shear rate, the time scale of gelation can be tuned from hours to nearly instantaneously by varying the shear rate and solution concentration. The shear-activated gels are distinct in their structure and rheological properties from thermoreversible gels. At a fixed concentration, the induction time prior to gelation decreases exponentially with the shear rate. This result indicates that shear-activated thermalization of the electrostatically stabilized rods overcomes the energy barrier for rod–rod contact, enabling rod fusion and subsequent irreversible network formation.
ISSN:2161-1653
2161-1653
DOI:10.1021/acsmacrolett.0c00168