Hydrophobic study of increasing alkyl chain length of platinum surfactant complexes: synthesis, characterization, micellization, thermodynamics, thermogravimetrics and surface morphology

Abstract

This paper contains details on the synthesis, characterization, physicochemical properties and surface morphology of five supramolecular metallosurfactants (SMMSs). The K₂PtCl₄ reaction with a series of cationic N,N,N-trimethyl-1-ammonium bromide (C_nTAB) surfactants yielded pink/green SMMSs. Electron deficient N⁺ of C_nTAB and electron rich [PtCl₄]²⁻ of K₂PtCl₄ coloumbically align to develop a chemical linkage. These SMMSs with increasing alkyl chains are abbreviated as MOTA, MDTA, MDDTA, MTDTA and MHDTA containing 8, 10, 12, 14 and 16 carbon atoms (n) respectively. The SMMSs are characterized by a CHN Analyzer, FTIR, UV-Vis and ¹H NMR. UV-Vis studies in DMSO, DMSO + water and DMSO + PBS (pH 7.2) predicted molecular sustainability. Their critcal micelle concentration (CMC) at 298.15, 308.15 and 318.15 K, calculated by conductivity and supported by surface tension measurements, has depicted self-aggregation which decreased on increasing alkyl chain length. Their increasing alkyl chain modulated their thermodynamic parameters which favours their micellization. Thermal decomposition and transition temperatures have facilitated their activation energy calculation with five different methods, which have depicted higher thermal stability. Differential Thermal Analysis (DTA) for heat flow predicted their endothermic and exothermic thermodynamics. Surface morphology and their particle size distribution analyzed by Scanning Electronic Microscopy (SEM), Atomic Force Microscopy (AFM) and Dynamic Light Scattering (DLS) respectively have confirmed their effective micellization on increasing alkyl chain length.