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boxylic acid group is diluted within the monolayer
surface. The microenvironment of COOH groups in a
mixed monolayer is different from that of a pure COOH
surface. We will determine the pKa of mixed monolay-
ers, where the carboxylic acid group is diluted within
the monolayer surface, including both hydrophobic and
hydrophilic dilution experiments, so as to develop a
better understanding of the behavior of this interfacial
chemistry. For example, dilution with hydrophobic
chains would create a low dielectric microenvironment
around the COOH groups that should make it difficult
for COOH groups to be deprotonated. On the other
hand, the lack of intermolecular hydrogen bonding
could lead to a lower pK and make the acid groups easier
to deprotonate. Variations in these effects as the diluent
is varied between hydrophobic and hydrophilic groups
will be most informative. Work in this direction, devel-
oping even more sensitive FTIR capabilities so as to
allow titration of submonolayer acid concentrations, is
underway.
Acknowledgments. Financial support of this work by the
Minerva Center for Microscale and Nanoscale Particles and
Films as Tailored Biomaterial Interfaces and by the Israel
Science Foundation is gratefully acknowledged.
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Gershevitz et al. / Carboxylate SAMs