2 research outputs found
Injectable Interpenetrating Network Hydrogels via Kinetically Orthogonal Reactive Mixing of Functionalized Polymeric Precursors
The enhanced mechanics, unique chemistries,
and potential for domain
formation in interpenetrating network (IPN) hydrogels have attracted
significant interest in the context of biomedical applications. However,
conventional IPNs are not directly injectable in a biological context,
limiting their potential utility in such applications. Herein, we
report a fully injectable and thermoresponsive interpenetrating polymer
network formed by simultaneous reactive mixing of hydrazone cross-linked
poly(<i>N</i>-isopropylacrylamide) (PNIPAM), and thiosuccinimide
cross-linked poly(<i>N</i>-vinylpyrrolidone) (PVP). The
resulting IPN gels rapidly (<1 min) after injection without the
need for heat, UV irradiation, or small-molecule cross-linkers. The
IPNs, cross-linked by kinetically orthogonal mechanisms, showed a
significant synergistic enhancement in shear storage modulus compared
to the individual component networks as well as distinctive pore morphology,
degradation kinetics, and thermal swelling; in particular, significantly
lower hysteresis was observed over the thermal phase transition relative
to single-network PNIPAM hydrogels
Nanostructure of Fully Injectable Hydrazone–Thiosuccinimide Interpenetrating Polymer Network Hydrogels Assessed by Small-Angle Neutron Scattering and dSTORM Single-Molecule Fluorescence Microscopy
Herein,
we comprehensively investigate the internal morphology
of fully injectable interpenetrating networks (IPNs) prepared via
coextrusion of functionalized precursor polymer solutions based on
thermoresponsive poly(<i>N</i>-isopropylacrylamide) (PNIPAM)
and nonthermoresponsive poly(vinyl pyrrolidone) (PVP) by reactive
mixing using kinetically orthogonal hydrazone and thiosuccinimide
cross-linking mechanisms. Small-angle neutron scattering, probing
both the full IPN as well as the individual constituent networks of
the IPN using index-matching, suggests a partially mixed internal
structure characterized by PNIPAM-rich domains entrapped in a clustered
PVP-rich phase. This interpretation is supported by super-resolution
fluorescence microscopy (direct stochastic optical reconstruction
microscopy) measurements on the same gels on a different length scale,
which show both the overall phase segregation typical of an IPN as
well as moderate mixing of PNIPAM into the PVP-rich phase. Such a
morphology is consistent with the kinetics of both gelation and phase
separation in this in situ gelling system, in which gelation effectively
traps a fraction of the PNIPAM in the PVP phase prior to full phase
separation; by contrast, such interphase mixing is not observed in
semi-IPN control hydrogels. This knowledge has significant potential
for the design of an injectable hydrogel with internal morphologies
optimized for particular biomedical applications