latter underwent thiol–yne click reaction with alkyne-terminated
PCL, prepared by ring-opening polymerization of 3-CL in the
presence of propargyl alcohol, to produce the PCL-click-PNI-
2
PAM AB -type copolymer. Microporous membranes with
surface-enriched PNIPAM chains were prepared from the NMP
solution of the PCL-click-PNIPAM copolymers by phase
inversion in an aqueous medium. The tertiary C–Br groups of the
PNIPAM chain ends on the PCL-click-PNIPAM membrane and
pore surfaces provide functionalities for the surface-initiated
ATRP of NaSS to produce the PCL-click-PNIPAM-b-PNaSS
membranes. The temperature and electrolyte responsive char-
acteristics of the PCL-click-PNIPAM and PCL-click-PNIPAM-
b-PNaSS membranes were illustrated by the swelling experiments
and glucose transport behavior. The stimuli-responsive
membranes with low cytotoxicity, obtained via the present
approach, have potential applications in biomedical areas, such
as drug delivery and tissue engineering.
Fig. 10 Cytotoxicity assays of the (a) PCL, (b) PCL-click-PNIPAM1,
0
(
c) PCL-click-PNIPAM2, (d) PCL-click-PNIPAM3, and (c ) PCL-click-
PNIPAM2-b-PNaSS membranes of 1 cm ꢂ 1 cm in area in 3T3 fibro-
blasts culture medium after 24 h of incubation. Error bars represent the
standard deviation of four measurements.
PCL-click-PNIPAM2-b-PNaSS membranes exhibit higher
permeation rates in 1 M NaCl than in deionized water (Fig. 9). In
deionized water, the strong electrostatic repulsion among the
sulfate anions forces the PNaSS side chains to adopt a highly
extended conformation. On the other hand, due to the electro-
static screening effect, the electrolyte will shield the intrachain
and interchain electrostatic repulsion among sulfate anions. The
PNaSS brushes on the membrane and pore surfaces undergo
association and aggregation as a result of the polyelectrolyte
effect. Steric obstruction to transport through the pores of the
membrane is substantially reduced, resulting in the increase in
permeation rate through the microporous membrane. This
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. Conclusions
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This journal is ª The Royal Society of Chemistry 2012
J. Mater. Chem., 2012, 22, 16248–16258 | 16257