Paper Number
SF4 

Session
Surfactants, Foams, and Emulsions

Title
Humidity affects the rheology of supramolecular organogels

Presentation Date and Time
October 21, 2019 (Monday) 11:05

Track / Room
Track 5 / Room 306A

Authors (Click on name to view author profile)

1. Vereroudakis, Emmanouil (FORTH-IESL)
2. Vlassopoulos, Dimitris (FORTH, Institute of Electronic Structure & Laser)

Author and Affiliation Lines (in printed abstract book)
Emmanouil Vereroudakis and Dimitris Vlassopoulos
Institute of Electronic Structure & Laser, FORTH, Heraklion 70013, Greece

Speaker / Presenter 
Vereroudakis, Emmanouil

Text of Abstract
Supramolecular organogelators have been known for more than 30 years, however the surprisingly extraordinary sensitivity of their self-assembly and viscoelastic properties to humidity have been ignored until recently[1,2]. It turns out that organic oils typically contain tiny quantities of water (0.01% by weight) which can influence the self-assembly as well as the flow properties of supramolecular gelators they contain[1,2]. Here we explore the properties of biphenyl tricarboxamides (BPTA) in dodecane which exhibit structural transitions with varying temperature. The driving force behind these transitions is the fact that the humidity content of the supramolecular polymer changes with temperature. The present system is investigated using shear rheology under controlled humidity conditions in both humid (~60% relative humidity) and dry (~5% relative humidity) conditions. We observe that in a humid environment the linear and non-linear rheological properties are affected by the temperature. Equivalently, the humidity content in the supramolecular polymer tunes its rheology at constant temperature. At temperatures where the system does not interact with water,we observe the higher plateau modulus, slower relaxation time and substantial strain-hardening under shear. On the other hand, at temperatures where the systems strongly interacts with water the plateau modulus is lower, the relaxation faster and there is absolutely no sign of strain hardening behavior. These findings suggest that humidity effects cannot be dismissed when working with oily environments. They also provide new insights into tailoring the flow properties of organogels.

Work in collaboration with N. J. Van Zee, E. W. Meijer (Techonological University of Eindhoven).

References
1. N.J. Van Zee et al., Nature, 558, 100-103 (2018)
2. A. Louhichi et al., J. Rheol. 61, 1173-1182 (2017)