Mobility of SDOSS powered by ionic interactions in Sty/n-BA/MAA core-shelllatex films. 21. A spectroscopic study

While molecular level interactions between sulfonate groups of sodium dioct ylsulfosuccinate (SDOSS) and COOH groups in styrene/n-butyl acrylate/methac rylate 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 group s 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 a nd how it may alter polymer contractions and release of entropically attach ed molecules to interfacial regions. These studies show that the release of SDOSS molecules from MAA containing Sty/n-BA particles is attributed to tw o factors: (1) entropic effect, due to increased compatibility resulting fr om surfactant penetration into latex particle surfaces and (2) enhanced par ticle out-layer glass transition temperature (Tg) The SDOSS release is inhi bited when surface neutralization levels are 0-25%, but at higher degrees o f neutralization (50-100%), excessive SDOSS exudation to the film-air (F-A) interface of a film is observed. This behavior is attributed to the displa cement of SDOSS molecules from MAA-containing latex particles during film f ormation as a result of the conversion of potential surface energy into mec hanical movement when ionic bonds are broken. Thus, the simultaneous presen ce of p-MAA and SDOSS at the particle surfaces make them act as polyelectro lytes, responding to chemical changes, and during film formation, ionomeric species containing SO3-Na+-COO-Na+ entities near the F-A interface are for med.