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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.

Perfume microcapsules for laundry applications are extensively used in home and consumer care products. Capsules have to bind into the fabric during washing and survive the rinsing and drying steps until the desired moment of rupture, usually when in contact with the skin. In order to assess the performance of the microcapsules in the different steps, quantification methods are required. It is reported here the first methodology, using fluorescence microscopy, whereby the number and size of fluorescent microcapsules is individually determined in large fabric areas using image analysis. The performance of fluorescent melamine-formaldehyde perfume microcapsules of two different sizes under abrasion is studied using smooth and rough surfaces, under dry and wet conditions. Survival profiles are obtained with the number of abrasion passes, allowing for characterizing the performance of microcapsules under different conditions. In addition to quantification, fluorescence and optical microscopy allow for identifying where are the capsules deposited in the fabric, as well as which are the safest zones that allow microcapsules to survive extensive abrasion.

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