Surfactant concentration and morphology at the surfaces of acrylic latex films
1999; Elsevier BV; Volume: 35; Issue: 1-4 Linguagem: Inglês
10.1016/s0300-9440(99)00017-x
ISSN1873-331X
AutoresA. Tzitzinou, P.M. Jenneson, A.S. Clough, Joseph L. Keddie, Jian R. Lu, P. A. Zhdan, K. E. Treacher, R. Satguru,
Tópico(s)Pickering emulsions and particle stabilization
ResumoThe final outcome of surfactants during latex film formation is a topic of ongoing concern and interest. In this study of an acrylic latex containing an anionic surfactant, two notable phenomena are observed. (1) A higher surfactant concentration is present at the air surface of the latex films, regardless of the film-forming temperature and time. In some cases, surfactant is not visible in an atomic force microscope (AFM) image as a separate phase, but compositional profiles obtained with Rutherford backscattering spectrometry (RBS) reveal an enhanced concentration of surfactant over a depth from the surface that is comparable to the latex particle diameter. (2) The surfactant features that are imaged with the AFM evolve from a thin uniform layer, to a `finger-like' morphology, to small flat droplets, and finally to larger, hemispherical `blobs.' We suggest that surfactant is first deposited from the air/water interface onto the latex surface during the drying process. During this progression in the morphology of the surfactant, the ratio of the surface area-to-volume decreases. We speculate that this phenomenon is driven by a reduction in surface energy.
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