Self-assembly of surfactants into micellar structures plays an important role in nano applications. Examples include nanoparticle synthesis, nanoemulsion stabilisation and drug delivery systems. The chemical structure of the surfactant has a big impact on the size and shape of the micellar structures, and hence on the properties of the final material.
Building an experimental phase diagram in a wet lab is a complex and time-consuming task. From the preparation to the analysis of samples through imaging techniques, one must work very accurately. All these steps are prone to human error which may lead to a large deviation in the results.
Simulations are powerful predicting tools that decrease the sensitivity to human error and can provide insightful trends and qualitative data. In this use case, we focus on predicting the transition from a lamellar to a discontinuous cubical phase for the polyoxyethylene oleyl ether, POE(n), surfactant by increasing the hydrophilic chain (n) from 5 to 20 units.
We make use of our molecular engine to set up and run the simulations. Here, we only need to input the molecular structure in terms of SMILES code to generate our virtual ingredient (Figure 1). Then, we simply choose the concentration of surfactant and the simulation is ready to run.
Figure 1. a) 3D visualisation of the POE(5) molecule used in our simulations, b) chemical structure of POE(n) and c) description of the molecule units created during the coarse-graining of the SMILES.
We have selected surfactant concentrations that lead to completely different micellar structures for each chain length to evaluate the predictive power of RheoCube. The results show a clear transition from a lamellar phase POE(5), passing through a hexagonal phase POE(10) to an discontinuous cubical phase POE(20) in agreement with the experimental data (Figure 2).
Figure 2. Snapshots taken from our simulations for the POE(5), POE(10) and POE(20) systems include an inset of the expected micellar phase from the experimental data.
Using RheoCube to predict the transition between phases for concentrated surfactant systems saves experimental time and costs. Rheocube makes it possible to prepare multiple samples and set up multiple experiments in parallel to give you insights faster. Insights that can aid you in taking smarter decisions and reducing lab experiments.