A metal binding to polycarboxylic acids is an important phenomenon in systems ranging from environmental to industrial. For example, humic substances are a naturally occurring class of polycarboxylic acids that are able to bind to toxic metals in the environment. These substances are known to be surface active, so there is an interest in studying their behavior with the metal cations at environmentally relevant fluid interfaces (such as the oil-water interface) in order to better understand the fate and transport of the toxic metals in the environment. Instead of studying humic substances, the adsorption and assembly of isotactic poly(methacyrlic) acid (iPMA) to the CCl4-H2O interface in the presence of metal cations is used as a model environment system using vibrational sum frequency spectroscopy (VSFS) and interfacial tension measurements. VSFS is able to show the initial adsorption behavior of the iPMA to the interface and revealed that iPMA is not surface active at a pH greater than 4.5, while is surface active at a pH less than 4.5 without the presence of metal cations. iPMA is also only able to form a monolayer to the CCl4-H2O interface in either pH range. The presence of the metal cations does not change the behavior of iPMA at a pH less than 4.5. However, at pH greater than 4.5, the metal cations induce the iPMA to the interface to make iPMA surface active, but does not induce more layers to the interface.

Effects of ions and acidity on the assembly of polyelectrolytes at the oil-water interface

247th National Meeting (2014)

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