Thermoresponsive nanocomposite double network hydrogels

Abstract

The utility and efficacy of thermoresponsive poly(N-isopropylacrylamide) (PNIPAAm) hydrogels as smart materials is limited by their physical properties. In this study, we sought to design PNIPAAm nanocomposite hydrogels which displayed enhanced mechanical properties as well as deswelling–reswelling kinetics but without reducing equilibrium swelling or altering the convenient volume phase transition temperature (VPTT) of PNIPAAm. PNIPAAm hydrogels were formed as double networks (DN) comprised of a tightly crosslinked 1st network and a loosely crosslinked 2nd network. In addition, polysiloxane nanoparticles of two different average diameters (~50 nm and ~200 nm) were incorporated during formation of the 1st or 2nd network. The influence of the hydrogel composition on VPTT, morphology, equilibrium swelling, deswelling–reswelling kinetics and mechanical properties was evaluated. We observed that DN hydrogels formed with ~200 nm polysiloxane nanoparticles introduced during formation of the 1st network achieved the best combination of the desired properties.

Self-Cleaning Membrane to Extend the Lifetime of an Implanted Glucose Biosensor

“…17 The “1 st network precursor solution” was formed by combining NIPAAm monomer (1.0 g), NVP co-monomer (0.16 g), BIS crosslinker (0.04 g), polysiloxane nanoparticle emulsion (0.485 g), Irgacure-2959 photoinitiator (0.08 g) and DI H 2 O (6.54 g). The “2 nd network precursor solution” was formed by combining NIPAAm (6.0 g), NVP (0.96 g), BIS (0.012 g), Irgacure 2959 (0.24 g), and DI H 2 O (21.0 g).…”

“…Recently, we reported a double network nanocomposite (DNNC) hydrogel comprised of an interpenetrating, asymmetrically crosslinked PNIPAAm matrix with polysiloxane nanoparticles (~200 nm diameter) embedded during formation of the first network. 17 This DNNC hydrogel exhibited significantly improved thermosensitivity in terms of both the rate and the extent of deswelling and reswelling versus a conventional PNIPAAm hydrogel. Furthermore, the DNNC hydrogel exhibited improved modulus and strength.…”

Multiresponsive Hyaluronan‐p(NiPAAm) “Click”‐Linked Hydrogels

“…RAFT methodology was used for the synthesis of copolymers and terpolymers with hydrophobic (styrene) and hydrophilic ( N ‐acryloylmorpholine, N‐isopropylacrylamide) sequences in the backbones . Other applications concern the entrapment of p(NiPAAm) in inert or non‐responsive network in order to introduce thermosensitivity while maintaining unchanged the mechanical properties …”

Thermoresponsive Double Network Micropillared Hydrogels for Controlled Cell Release

“…While PNIPAAm IPNs have been reported to enhance mechanical properties, their swelling was diminished . In contrast, we recently prepared a PNIPAAm DN hydrogel and compared their properties to the analogous SN hydrogel . The VPTT of the DN hydrogel was not altered versus that of the SN hydrogel but the modulus was nearly doubled.…”

“…As noted above, PNIPAAm SN hydrogels formed as mm‐thick planar slabs exhibit limited thermosensitivity. While the PNIPAAm DN design improves thermosensitivity, reduction of hydrogel size to the micron‐scale takes advantage of the fact that the kinetics of deswelling/reswelling are proportional to the square of the smallest dimension . Given this, PNIPAAm SN hydrogels have been prepared as micron‐scale pillars and their thermosensitivity and cell‐release behavior evaluated …”