| Grant number: | 12/15147-4 |
| Support type: | Regular Research Grants |
| Duration: | June 01, 2013 - May 31, 2015 |
| Field of knowledge: | Physical Sciences and Mathematics - Chemistry - Physical-Chemistry |
| Principal researcher: | André Farias de Moura |
| Grantee: | André Farias de Moura |
| Home Institution: | Centro de Ciências Exatas e de Tecnologia (CCET). Universidade Federal de São Carlos (UFSCAR). São Carlos , SP, Brazil |
Abstract
This research project describes the computational theoretical study of the thermodynamic potentials which are responsible for the spontaneous formation of self-assembled and self-organized structures in aqueous solution. Molecular dynamics simulations will be performed in order to study a prototypical micellar system. The relaxation times for systems like these are prohibitively long, so that in general a spontaneous association cannot be observed during the course of a typical molecular dynamics if realistic potentials should be employed, since the potential surface becomes too much complex to be sampled within the total duration reached by the integration of the equations of motion. This difficulty is particularly real for the calculation of entropic properties, as the entropy cannot be obtained as an ensemble average, being necessary, in principle, to know all the accessible states of the system in its phase space. Thus, our research proposal is focused on the usage of alternative techniques to study thermodynamic potentials, including the entropic ones, along the reaction coordinates describing the association/dissociation of surfactant molecules into micelles. More specifically, we shall perform molecular dynamics simulations with the umbrella sampling potential to map the potential of mean force during the removal of one molecule from the aggregates under study. The potential of mean force describes the Gibbs energy variation along the reaction coordinate, being possible to split it into its enthalpic and entropic components. It is possible as well to separate the contributions arising from the head and the apolar tail, evaluating quantitatively for the first time the effect of each part on the thermodynamics of the process. (AU)
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