pH-Responsive MFPTT microcapsules containing dimethyl sulfoxide: Preparation, characterization and tuning the release behavior of microcapsule contents

The new approach to intelligent systems is the use of stimuli-responsive micro/nanocapsules to release active ingredients. This work focuses on the preparation of melamine formaldehyde pentaerythritol tetrakis (3-mer-captopropionate) (MFPTT) microcapsules and represent a versatile platform to encapsulate active agent that release capsule contents under alkaline condition. Dimethyl sulfoxide (DMSO) was selected as a solvent that can dissolve a wide range of chemical compound. Experimental results demonstrated that the properties of the capsule shell play a key role in the release rate. Permeability and release of encapsulated payloads were investigated by Field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), Xray diffraction (XRD) and ultraviolet-visible spectroscopy (UV-vis). It is found that the morphology of capsules was affected by changing the pH-sensitive agent content. The particle size of capsules that were synthesized at different conditions were in the range of 800 to 9000 nm with a polydispersity index < 0.4. The chemical structure of capsules was investigated with Fourier-transform infrared spectroscopy (FTIR), Elemental analysis (ICP) and Energy-dispersive X-ray (EDX). The shell thickness and core fraction of the microcapsules were characterized by using thermogravimetric analysis (TGA). Additionally, the performance of the release inhibitor from microcapsules in the interface of the coating/substrate characterized by electrochemical impedance spectroscopy (EIS) measurement.