Structure and mechanical properties of consumer-friendly PMMA microcapsules

Environmentally and consumer-friendly poly(methyl methacrylate) (PMMA) microcapsules were prepared on the basis of an in situ polymerization reaction to encapsulate perfume oil, which aims to be delivered to fabric surfaces via liquid detergents. Microcapsules with a narrow size distribution were produced using a membrane emulsification system; results were compared with a standard homogenization procedure. The shell thickness of microcapsules was found to increase with the polymerization reaction time, which was measured using a lipophilic fluorescent dye dissolved in the perfume oil and confocal laser scanning microscopy. Microcapsules with a wide range of shell thicknesses could be produced by modifying the reaction time. The force versus displacement profiles obtained from compression of single such microcapsules between two parallel surfaces based on micromanipulation were very different: thin-shell microcapsules burst under compression, whereas thick-shell microcapsules did not. However, the intrinsic mechanical properties of the PMMA shells, determined with finite element modeling (FEM) and the experimental data, such as the elastic modulus and the rupture stress, were found independent of the reaction time. The microcapsules with a wide range of shell thicknesses may be used to encapsulate different oil-based active ingredients for potential industrial applications.