Intra- and intermolecular interactions are important for
the surface properties of polymers. Jiang et al.[16] have
reported that at temperatures above the lower critical
solution temperature (LCST), the compact, collapsed conformation
of poly(N-isopropylacrylamide)(PNIP AAm)
chains induced by intramolecular hydrogen bonding between
the C=O and NHgroups in the main PNIPAAmchains leads
to a low surface free energy and high contact angle for water.
When the temperature is below the LCST, however, the
predominantly intermolecular hydrogen bonding between the
main PNIPAAm chains and water molecules leads to a higher
surface free energy and lower water contact angle. In
addition, Chung et al.[17] have reported that the presence of
amide groups in a fluorinated-main-chain liquid-crystalline
polymer system tends to induce strong intermolecular hydrogen
bonding, which results in higher surface free energies and
higher degrees of hydrophilicity. According to these previous
studies, it appears that intramolecular hydrogen bonding
tends to lower the surface free energy more than intermolecular
hydrogen bonding between main polymer chains.