Yq. Zhao et Mw. Urban, Mobility of SDOSS powered by ionic interactions in Sty/n-BA/MAA core-shelllatex films. 21. A spectroscopic study, LANGMUIR, 16(24), 2000, pp. 9439-9447
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.