Mobility of SDOSS Powered by Ionic Interactions in Sty/n-BA/MAA Core−Shell Latex Films. 21. A Spectroscopic Study

Abstract

While molecular level interactions between sulfonate groups of sodium dioctylsulfosuccinate (SDOSS) and COOH groups in styrene/n-butyl acrylate/methacrylate acid (Sty/n-BA/MAA) copolymer particles have been the subject of our earlier studies, the main focus of this work is to establish how MAA groups affixed to polymer latex particle surfaces will affect SDOSS mobility in Sty/n-BA/MAA latex films. The ultimate objective is to develop a series of model systems simulating the degree of neutralization of polymer surfaces and how it may alter polymer contractions and release of entropically attached molecules to interfacial regions. These studies show that the release of SDOSS molecules from MAA containing Sty/ n-BA particles is attributed to two factors: (1) entropic effect due to increased compatibility resulting from surfactant penetration into latex particle surfaces and (2) enhanced particle out-layer glass transition temperature (Tg). The SDOSS release is inhibited when surface neutralization levels are 0-25%, but at higher degrees of neutralization (50-100%), excessive SDOSS exudation to the film-air (F-A) interface of a film is observed. This behavior is attributed to the displacement of SDOSS molecules from MAAcontaining latex particles during film formation as a result of the conversion of potential surface energy into mechanical movement when ionic bonds are broken. Thus, the simultaneous presence of p-MAA and SDOSS at the particle surfaces make them act as polyelectrolytes, responding to chemical changes, and during film formation, ionomeric species containing SO3 -Na + -COO -Na + entities near the F-A interface are formed.

Lateral surface nonuniformities in drying latex films

“…Convection is a primary mechanism for surfactant transport,8 and hence nonuniformities in drying lead to lateral inhomogeneities in the surfactant distribution within the film. The existence of lateral surfactant inhomogeneities at the film surface has been confirmed through atomic force microscopy9 and optical imaging 10. These surfactant concentration gradients lead to surface tension gradients.…”

Thinning of drying latex films due to surfactant

“…Although intuitively the drying process of a latex film should be uniform, lateral non-uniformities are commonly observed and have been quantified [5]. As surfactant transport primarily occurs through the water flux [6], non-uniform drying leads to lateral nonuniformities in the surfactant distribution within the film and at the air-water interface which has been confirmed by several groups using atomic force microscopy [7] and optical imaging [8].…”

Stimuli-Responsive Surfactant/Phospholipid Stabilized Colloidal Dispersions and Their Film Formation

“…[1][2][3][4][5][6][7][8][9][10][11][12] Thus, continuous quests for advancing our knowledge continue by exploring new avenues. For example, it has not been realized until recently that their synthesis may be facilitated by amphiphilic bioactive molecules, such as phospholipids, 13,14 and this approach opened up new scientific and application avenues of polymeric colloidal dispersions.…”