Molecular migration concerns a huge number of industrial systems containing mobile components in polymer matrices. The behavior of surfactants at polymer interfaces is relevant to a wide range of systems in which polymer films encounter surfactant-rich environments. Although the surface and bulk properties of large polymers in solution is well studied and the adsorption of surfactants onto liquid surfaces has been extensively characterized, the case where the solution is replaced by a solid polymer has received little attention. Predicting the behavior of surfactants in polymer films therefore remains a fundamental scientific challenge. In this work, attempts are made to isolate parameters responsible for the blooming of additives from poly(vinyl alcohol) (PVA) in order to ultimately predict and control segregation<br/>The segregation of surfactants from PVA films has been explored using neutron reflectivity to depth profile additives and a rich and diverse range of behaviors has been identified. When PVA contains the anionic surfactant sodium dodecyl sulfate, a wetting layer of surfactant on the film surface is formed. In the presence of an additional plasticizer (glycerol) this SDS surface excess is greatly enhanced, and smectic nanostructures are formed on the surface, consisting of surfactant lamellae separated by interstitial glycerol layers. In contrast, the segregation of a zwitterionic surfactant from PVA reflects behavior commonly observed in solution, where a monolayer of surfactant covers the surface but the remaining additive is distributed evenly throughout the bulk polymer.<br/>Studies of the polymer and additives in aqueous solution enable identification of driving forces for this behavior. Surface energy arguments can be used to rationalize segregation to a great extent, but cannot alone explain the plasticizer enhancement of the surface excess of SDS or wide range of segregation behaviours observed. We therefore utilize the phase behavior of model systems to determine the compatibility of film components, assessing this a likely driving force for segregation from the polymer.

Small molecule segregation from poly(vinyl alcohol) films

2019 Fall National Meeting

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