Optimization of synthesis parameters for polyurea microcapsules via interfacial polymerization: effects of solvent, phase ratio, and monomer structure on capsule morphology and thermal properties

Mohammad Yolmeh, Amir Abdolmaleki, Hossein Soleimani, Masoud Riazi

2026

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DOI 10.1016/j.mtcomm.2026.116215
Data confidence 70 medium
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Abstract

Polyurea microcapsules were synthesized via interfacial polymerization of toluene diisocyanate (TDI) with amine monomers in a water-in-oil (W/O) emulsion system. This study systematically investigates the effects of key synthesis parameters including organic solvent type, aqueous-to-organic phase ratio, and amine monomer molecular structure on capsule morphology, chemical structure, and thermal properties. Scanning electron microscopy (SEM) revealed that a 4:1 (v/v) heptane–chloroform solvent mixture combined with a 20:80 aqueous-to-organic phase ratio produced spherical capsules with smooth surfaces and uniform shell thickness. Comparative analysis showed that ethylenediamine (EDA) yielded stronger and more cohesive shells than isophorone diamine (IPDA), attributed to its higher reactivity and lower steric hindrance. Fourier-transform infrared spectroscopy (FTIR) confirmed the formation of urea linkages, while thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) demonstrated thermal stability up to approximately 200°C with a glass transition temperature near 60°C. These findings establish a foundation for the rational design of polyurea microcapsules for potential controlled-release applications.