A dual-responsive hydrogel based on graphene oxide (GO) was prepared by in situ radical copolymerization of N-isopropyl acrylamide (NIPAM) as a temperature-sensitive component and acrylic acid (AA) as a pH-sensitive unit. The resulting hydrogels (GO/poly­(NIPAM-co-AA) (PNA) were systematically characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, thermogravimetric analysis, differential scanning calorimetry, and scanning electron microscopy. With the change of AA content, the lower critical solution temperature of hydrogels changed from 26.91 to 24.38 °C. The swelling ratio under alkaline condition was higher than that under acidic condition. The adsorption of rhodamine B (RB) followed Langmuir isotherm model and pseudo-second-order model, and nearly 93% of RB could be released within 10 h at pH 4.01 and 60 °C. With imidacloprid as the model drug, the higher cumulative release rate of the GO/PNA hydrogel was obviously observed at pH = 4.01 than at pH = 9.18. On the basis of their good adsorption–desorption, loading-releasing, and regeneration ability, the GO/PNA hydrogel as a multifunctional adsorbent might have broad application prospects in environmental protection and biomedical engineering.

No abstract

As a kind of attractive biomaterial, stimuli-responsive hydrogel had been widely used in wound dressings and wearable devices. However, it remained challenging to prepare a hydrogel with both excellent self-adhesion and self-healing performances. Inspired by the adhesion mechanism of mussel, we prepared a self-adhesive, self-healing, and triple-responsive hydrogel by a hybrid system based on tunable composition of polydopamine (PDA) and polymer network composed of poly­(N,N-diethylacrylamide-co-acrylic acid). It was found that the resulting hydrogel could be directly adhered to a variety of substrates without the need of external adhesives on account of the existence of enough free catechol groups in the hydrogel. Due to the synergistic effect of PDA nanoparticles and polymer network, hydrogel also showed excellent self-healing property. Moreover, we demonstrated that the triple-responsive hydrogel as an adsorbent could efficiently remove methylene blue, and the maximum adsorption capacity was 305.4 mg/g when the optimum mass fraction of PDA was 0.4 wt % in hydrogel. The adsorption of the hydrogel toward methylene blue could be well simulated by pseudo-second-order model and Langmuir isothermal adsorption model. From the viewpoint of mechanism, methylene blue molecules could be directly adsorbed to these carboxyl, amino and catechol functional groups in the molecular structure of polymeric hydrogels by electrostatic force, π–π interaction, Van Der Waals force, hydrogen bonding, etc. Ultimately, we hoped to extend this hybrid strategy to develop multifunctional hydrogels and consequently broaden the application prospects of hydrogels in biomedical treatment and environmental protection.

No abstract

No abstract