Journal of Dental Research, Vol 72, 1418-1422, Copyright © 1993 by International & American Associations for Dental Research Online Journals
Adsorption of low-molecular-weight sodium polyacrylate on hydroxyapatite
D. N. Misra
American Dental Association Health Foundation, Paffenbarger Research Center, National Institute of Standards and Technology, Gaithersburg, Maryland 20899.
Adsorption of low-molecular-weight sodium polyacrylate from aqueous
solution onto synthetic hydroxyapatite was studied at room temperature so
that the mechanism of adhesion of polyacrylate cements to tooth mineral
could be elucidated. The adsorption isotherm of sodium polyacrylate was
Langmuirian in shape and was thus qualitatively different from that of
polyacrylic acid (Misra, 1991), which exhibited an adsorption maximum. The
self-association of the molecules that probably causes the maximum to occur
with polyacrylic acid was effectively absent for the relatively
well-ionized, electrostatically repelling polyacrylate ions of the salt.
With the adsorption of acrylate ions, the concentration of phosphate ions
increased monotonically, while the concentration of calcium ions showed a
minimum. The adsorption of sodium polyacrylate was irreversible, as it was
for polyacrylic acid.
