Mechanical and microstructural characterization of poly(N-isopropylacrylamide) hydrogels and its nanocomposites

Abstract

Mechanical behavior dependency of the poly(N-isopropylacrylamide) hydrogel related to the amount of initiator, crosslinker, and nanoparticles was investigated. An experimental approach has been undertaken to observe these dependencies and assess the amount of initiator (ammonium persulfate), crosslinker (N, N′-methylene-bisacrylamide), and nanoparticles (graphene oxide) on the macroscopic responses of poly(N-isopropylacrylamide). Different amounts of initiator, crosslinker, and nanoparticle were used to manufacture specimens for the compression test. The specimens were subjected to compressive loading up to breakage to investigate the breaking behavior of poly(N-isopropylacrylamide). The responses of these specimens indicated that the mechanical behavior of poly(N-isopropylacrylamide) was highly nonlinear and depends on these ingredients. The mechanical responses of poly(N-isopropylacrylamide) were simulated using the ideal network model. The simulation results of the mathematical model substantially complied with the experimental data of poly(N-isopropylacrylamide). In addition, a more in-depth microstructural analysis was performed on these specimens. The analysis results allowed us to correlate the dependent amounts of the ingredients on the nonlinear, mechanical behavior of poly(N-isopropylacrylamide).

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

“…The hydrogel networks become compliant and unable to sustain stress attributed to low crosslinking concentration of MBA. Higher MBA concentration can increase the crosslinking density of the PNIPAm hydrogels, with the hydrogel network becoming more compact and the mechanical properties of hydrogels being improved 49 …”

“…Higher MBA concentration can increase the crosslinking density of the PNIPAm hydrogels, with the hydrogel network becoming more compact and the mechanical properties of hydrogels being improved. 49 Effect of SA concentration on properties of PNIPAm hydrogel Although the hydrogel shows good mechanical properties when the MBA concentration is 20 wt%, its poor swelling property cannot match the requirement of a fast response. Therefore, the TIP method was adopted and the MBA concentration was selected as 5 wt%.…”

Predicting the tensile and compressive modulus of electrospun fiber mat‐reinforced hydrogels using the Halpin–Tsai equations

“…One approach to improve the stiffness, strength, and toughness of hydrogels is to introduce fibrous reinforcement, for example with electrospun polymer mats or glass fibers. [7][8][9][10][11] Hydrogel-based systems for use in biomedical applications have been investigated that utilize this strategy, such as a polycaprolactone (PCL) fiber-reinforced polyethylene glycol (PEG) mimic of human vocal-fold tissue. 12 Mechanical models to describe the behavior of such composite materials are well developed for more conventional composites utilizing semicrystalline polymeric matrices, such as epoxy resins, and can be used to design materials with specific mechanical properties.…”

“…However, homogeneous hydrogels often display relatively poor mechanical properties, and do not replicate the complex, hierarchical materials found in nature. One approach to improve the stiffness, strength, and toughness of hydrogels is to introduce fibrous reinforcement, for example with electrospun polymer mats or glass fibers 7–11 . Hydrogel‐based systems for use in biomedical applications have been investigated that utilize this strategy, such as a polycaprolactone (PCL) fiber‐reinforced polyethylene glycol (PEG) mimic of human vocal‐fold tissue 12 .…”