Unveiling the phase behavior of CiEj non-ionic surfactants in water through coarse-grained molecular dynamics simulations


Poly(oxyethylene) alkyl ethers, usually denoted by CiEj surfactants, exhibit a rich phase behavior in water, self-assembling to form a variety of 3-D structures with a controllable morphology that find multiple applications across different industrial segments. Hence, being able to describe and understand the effect of molecular structure on the phase behavior of these systems is highly relevant for the efficient design of new materials and their applications. Considering the promising results obtained over the last decade using the MARTINI model to describe ethylene-oxide containing compounds, an extensive assessment of the ability of such a model to describe the phase behavior of CiEj in water was carried out and results are presented here. Given the overall poor temperature transferability of the MARTINI model, mostly due to the lack of an accurate representation of hydrogen bonding, simulations were carried out at a single temperature of 333 K, where most phases are expected to occur according to experiments. Different chain lengths of both the hydrophobic and hydrophilic moieties, spanning a wide range of hydrophilic-lipophilic balance values, were investigated and the phase diagrams of various CiEj surfactants explored over a wide concentration range. The model was able to satisfactorily describe the effect of surfactant structure and concentration on mesophase formation. The stability and dimensions of the obtained phases, and the prediction of some unique features such as the characterization of a singular lamellar phase are presented. The results obtained in this work highlight both the predictive ability and the transferability of the MARTINI forcefield in the description of such systems. Moreover, the model was shown to provide adequate descriptions of the micellar phase in terms of micelle dimensions, critical micelle concentration, and average aggregation number.



subject category

Chemistry, Physical; Materials Science, Multidisciplinary; Physics, Multidisciplinary; Polymer Science


Crespo, EA; Vega, LF; Perez-Sanchez, G; Coutinho, JAP

our authors


This work was developed within the scope of the projects CICECO-Aveiro Institute of Materials, UIDB/50011/2020 & UIDP/50011/2020 and SILVIA ref. CENTRO-01-0145-FEDER31002 financed by national funds through the FCT/MEC and when appropriate co-financed by FEDER under the PT2020 Partnership Agreement. E. A. Crespo acknowledges FCT for the PhD Grant SFRH/BD/130870/2017. German Perez-Sanchez acknowledges the national funds (OE), through FCT -Fundacao para a Ciencia e a Tecnologia, I.P., in the scope of the framework contract foreseen in numbers 4, 5 and 6 of article 23, of DecreeLaw 57/2016, of August 29, changed by Law 57/2017, of July 19. L. F. Vega acknowledges partial financial support from Khalifa University of Science and Technology under project RC2-2019-007.

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