Preparation and characterization of temperature‐responsive Ca–alginate/poly(N‐isopropylacrylamide) hydrogel

Abstract

Poly(N‐isopropylacrylamide) (PNIPAm) is widely implemented in responsive soft actuators. However, there are still defects of low brittleness and poor mechanical properties. Moreover, little attention has been paid to diameter shrinkage deformation of tubular PNIPAm hydrogels. In this study, physical crosslinking between Ca2+ cations and sodium alginate (SA) was introduced to form an interpenetrating network with chemically crosslinked PNIPAm, and then Ca–alginate/PNIPAm hydrogels were prepared. Molecular structure, surface morphology, swelling properties and mechanical properties were characterized. The results indicated that the pure PNIPAm hydrogel obtained using thermal initiation polymerization had better swelling and temperature‐responsive properties (with a maximum swelling ratio of 1134.65% and a fastest decrease rate of 318.45% min−1 in swelling ratio) compared to the hydrogel using ultraviolet polymerization. The mechanical properties the Ca/PNIPAm hydrogel were enhanced until the SA concentration exceeded 8 wt%. The compressive modulus of the hydrogel with SA concentration of 8 wt% (16.61 kPa) was increased by 10 times as compared with the pure PNIPAm hydrogel (1.42 kPa), and its corresponding elastic modulus increased by 47%. Moreover, a model soft actuator was prepared based on annular and tubular hydrogels. It had reversible diameter shrinkage behavior at 50 °C, and excellent temperature‐responsive property. The results reported herein provide valuable insight into the engineering application of temperature‐responsive PNIPAm‐based hydrogels. © 2022 Society of Industrial Chemistry.

Multifunctional Oxidized Succinoglycan/Poly(N-isopropylacrylamide-co-acrylamide) Hydrogels for Drug Delivery

“…Eventually, the compressive strength of OSG/P(NIPAM-AM) hydrogels decreased with increasing OSG concentration. The change in the mechanical properties of the hydrogel is due to the co-occurrence of chemical and physical crosslinking and the interpenetration of OSG chains and P(NIPAM-AM) networks [ 56 ]. As the OSG concentration increases, the gel network becomes looser as OSG chains into P(NIPAM-AM); thus, the compressive strength of the gel is relatively low.…”

Preparation and Properties of PDMS Surface Coating for Ultra-Low Friction Characteristics

“…Compared with the original PDMS, the PDMS characteristic absorption peaks of all the coating samples are reduced in intensity, and new absorption peaks appear at 3347, 1654, and 1451 cm –1 . Among them, the antisymmetric and symmetric stretching vibration peaks of −NH at 3347 cm –1 and the stretching vibration peak of CO at 1654 cm –1 are ascribed to the stretching vibration absorption peaks of amides. , The 1451 cm –1 is the in-plane bending vibration peak of CH in the −CH 2 – group. , This analysis also shows that the surfaces of all of the coating samples are covered with a polymer layer, and the surface of the coating contains hydrophilic groups such as hydroxyl groups. This leads to excellent hydrophilicity.…”

“…71,72 The 1451 cm −1 is the in-plane bending vibration peak of CH in the −CH 2 − group. 73,74 This analysis also shows that the surfaces of all of the coating samples are covered with a polymer layer, and the surface of the coating contains hydrophilic groups such as hydroxyl groups. This leads to excellent hydrophilicity.…”

Robust and Elastic Thermoresponsive Hydrogels with High Swelling Properties for Efficient Solar Water Purification

“…36 As can be seen in Figure 3c, the swelling rate of the hydrogels was greatly increased with the addition of DMAPS, which was 2150 and 3650% for the PNIPAm gels and D-PNIPAm gels, respectively, and 3600 and 3550% for the DC-PNIPAm gels and DCS-PNIPAm gels, respectively. 37 This implies that the equilibrium swelling ratio of the hydrogels is larger because of the polymer chain's extension and the improved interaction of hydrophilic monomers, such as DMAPS, with water molecules in greater amounts. Although the thick SA layer of DCS-PNIPAm gels restricts the gels' swelling, the swelling ratio of the gels still shows a significant improvement when compared to pure PNIPAm gels, albeit with a slight decline.…”