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Abstrak :
ABSTRAK
The interaction of cationic surfactant (CTAB, Cationic surfactant hexadecyl trimethyl ammonium bromide ((C₁₆H₃₃)N(CH₃)₃BR and TTAB, Tetradecyl trimethyl ammonium bromide ( )), a prevalent chemical in the industrial and natural processes, with water ( ) has been studied using GROMACS program and VMD program. In the following project, to simulate the CTAB and TTAB at air-water interface, GROMACS (Groningen Machine for Chemical Simulations) software is used. GROMACS is a molecular dynamics package designed for primary use of simulation of biochemical molecules like proteins, lipids, and nucleic acids that have a many complicated bonded interactions (GROMACS, 2010). Furthermore, to model and display the simulation, VMD (Visual Molecular Dynamics) program is used. VMD is intended for modeling, visualization and analysis of biological systems such as proteins, nucleic acids, lipid bilayer assemblies, etc. In this research project 13 simulations, 6 of these are successive simulations and the other 7 simulations have been included in the appendix. The simulations have been simulated to prove the following 3 hypotheses which are ssurfactants has an amphiphilic nature, surfactants adsorb on the interface between oil and water, lowering the interfacial tension and promoting mixing and surface potential measurement at the air-water interface increases surfactant-dependent manner in the air-water expanded transition region. Therefore with the addition of surfactant to the air-water interface, there will be a sudden increase of surface potential. The first seven simulations that have been included in the appendix were simulated to find the right charge distribution. All the observed results shown by these 13 simulations are not yet predictable or reliable; this is due to not the right amount of simulation time or the charge distribution of the cationic surfactant. The three kinds of observations (the density profile of the cationic surfactant, the surface tension of the cationic surfactant with water, and the surface potential of cationic surfactant with water) are very uncertain and therefore many more simulations are required to be completed in the future.