Formation of aqueous core polyamide microcapsules obtained via interfacial polycondensation: Optimization of the membrane formation through pH control

The formation of aqueous core polyamide microcapsules via interfacial polymerization of a polyoxypropylenediamine (JA) in water and sebacoyl chloride (CS) dissolved in organic phase is studied. The originality of this work consists, firstly in the use of a diamine, which is an oligomer and pH control of the aqueous phase, and secondly in the control of the chemical structure by advanced techniques such as 13C NMR and MALDI-TOF mass spectrometry. The aim was to determine the optimal conditions which allow the formation of microcapsules. Thus, the emulsification process was first investigated with the aim to optimize the stability of the emulsion, which precedes the formation and the control of the size of the microcapsules. The optimization of the formulation of the system was then considered, in terms of monomer ratio, surfactant concentration and most important the pH of the aqueous phase. The chemical structure of the microcapsules was studied by FTIR, 13C NMR and MALDI-TOF mass spectrometry. Thermal properties of the polyamide membranes were also studied by thermal gravimetric analysis (TGA). Optical microscopy and laser light diffraction allowed the determination of the size of the microcapsules. Finally, the morphology was observed by scanning electron microscopy (SEM).