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Raman spectroscopy and micro-Raman mapping have been used to study the distribution of different chemical components at the surface of coated papers. The paper coatings contain organic nanoparticles with a structure of poly(styrene-co-maleimide) and encapsulated vegetable oils. Raman spectroscopy is able to differentiate between various types of oil, i.e., polyunsaturated, monounsaturated, or saturated, and indicates that the degree of imidization and reactivity of the oil (amount of free oil) complement each other. The surface mapping over large areas (5 × 5 mm2) illustrates good homogeneity of the coating layer and even surface coverage. The imide and oil are homogeneously distributed within the coating itself without a tendency for agglomeration. The covered areas of imide and oil mostly overlap for polyunsaturated oils, while larger amounts of oil occur outside the imide zones for monounsaturated and saturated oils. The latter indicates that the oil is partly "free" within the coating and acts as a continuous binder phase. The surface mapping over smaller areas (1 × 1 mm2) shows the coating and cellulose covered areas are complementary. The surface maps confirm that interaction between the coating and paper substrate happens through hydrogen bonding. Heterogeneities in the coating are due to the presence of remaining ammonolyzed maleic anhydride precursors forming amic acid moieties. The organic phase, oil phase, and cellulose substrate can also be differentiated by principal component analysis of the surface maps. [ABSTRACT FROM AUTHOR]

Giving paper and polymer photochromic properties under laser irradiation is challenging due to the low resistance of these materials to heat, their flexibility, and their possibly irregular structure. However, we could successfully deposit TiO2/Ag/ TiO2 layers stacking on flexible white glossy paper and transparent polyethylene terephalate (PET) substrates using a reactive magnetron sputtering technique, and tailor coloration changes after laser irradiation, alternating visible and ultraviolet (UV) wavelengths. The sample colors are characterized by a panel of chromas depending on the irradiation conditions. We demonstrate that these chroma changes are due to morphological changes of Ag nanoparticles (NPs) after visible laser irradiation of the colored as-deposited sample. The process exhibits a good reversibility after subsequent UV irradiation due to the growth of new metallic Ag NPs. The colors displayed in diffuse reflection by the paper samples are more saturated than the ones displayed in regular transmission by PET samples. We demonstrate the efficiency of the photochromic process on such support by printing high resolution patterns exhibiting different colors depending on the observation conditions. [ABSTRACT FROM AUTHOR]