Preparation and characterization of poly(urethane–urea) microcapsules containing limonene. Kinetic analysis

ABSTRACT

The synthesis of poly(urethane–urea) shells (PUU) using poly(ethylene glycols) of different molecular weights and methylene-bis(4-cyclohexylisocyanate) was performed for the microencapsulation of limonene, using a step-growth polymerization process. The obtained microcapsules were structurally characterized by dynamic light scattering, optical microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis. The results showed that the core–shell microcapsules had spherical shape, a mean diameter in between 10 and 20 µm, and characteristic urethane-urea bonds. Furthermore, the molecular weight of polyol influences the entrapment efficiency, which ranged from 38 to 55%. The release data were analyzed by applying the Korsmeyer–Peppas model.

KEYWORDS:

• Core–shell polymer
• limonene
• microencapsulation
• step-growth polymerization
• structure-properties

Additional information

Funding

This work was cofinanced by the project POCI-01-0145-FEDER-006984-Associate Laboratory LSRE-LCM funded by FEDER funds through COMPETE 2020-Programa Operacional de Competitividade e Internacionalização (POCI) and by national funds through FCT-Fundação para a Ciência e a Tecnologia. The additional programs PEst-C/EQB/LA0020/2013, NORTE-07-0162-FEDER-000050, and NORTE-07-0124-FEDER-000012 also supported the work presented in this paper.