Preparation and characterization of a novel poly(urea–formaldehyde) microcapsules with similar reflectance spectrum to leaves in the UV–Vis–NIR region of 300–2500 nm

Abstract

A novel material with similar reflectance spectrum in the UV–Vis–NIR region of 300–2500 nm to leaves was developed by means of encapsulation. Hydrophilic poly(urea–formaldehyde) was employed as a wall-former, which tended to cure into solid on the exterior layer of the primary W/O emulsion containing chlorophyll in the oil phase as a core substance to generate microcapsules. In particular, the resultant poly(urea–formaldehyde) microcapsules were carefully characterized by UV-3600 UV–Vis–NIR spectrophotometer. The results indicated that the resultant green poly(urea–formaldehyde) microcapsules exhibited very similar spectral reflectance characteristics to leaves, and the similarity of the reflectance spectrum of green poly(urea–formaldehyde) microcapsules to that of plant leaves was up to 97.2% in the UV–Vis–NIR region of 300–2500 nm. In this regard, this new green poly(urea–formaldehyde) microcapsules is a promising candidate for materials with similar reflectance spectrum to leaves in the UV–Vis–NIR region of 300–2500 nm. The characterization of the microcapsules including FT-IR, SEM and FE-SEM were studied. Also, the factors influencing the reflectance spectrum in the UV–Vis–NIR region of 300–2500 nm of microcapsules were analyzed.