Stimuli-responsive hydrogels using dynamic covalent bonds (DCBs) as cross-links may exhibit simultaneously the stimuli-responsibility of the physical gels and stability of the chemical gels. We prepared well-defined, ketone-based polymers based on commercially available diacetone acrylamide (DAAM) by a reversible addition-fragmentation chain transfer (RAFT) polymerization technique. The polymers could react with hexanedihydrazide yielding hydrogels. The mechanics, flexible properties and gelator concentration of the hydrogels can be tuned by varying the ratio of DAAM. Gelation time and hydrogel stability were gravely affected by the pH of the surrounding medium. The hydrogels possess self-healing ability without any external stimuli and undergo switchable sol-gel transition by the alternation of pH. In addition, the hydrogels showed pH-responsive controlled release behavior for rhodamine B. These kinds of ketone-type acylhydrazone DCB hydrogels, avoiding the aldehyde component, may ameliorate their biocompatibility and find potential applications in biomedicines, tissue engineering, etc.
Adsorbents
that are capable of controllable pollutants adsorption
and release without secondary pollution are attractive in water treatment.
Here, we propose eco-friendly CO2 as a trigger to switch
the charge states and collapse–expansion transition of giant
microgels consisting of hydrophilic acrylamide and hydrophobic 2-(diethylamino)ethyl
methacrylate and demonstrated the on–off, selective, and recyclable
adsorption of anionic dyes on microgels under CO2 stimulation.
Apart from easy-handling separation from the water by a simple filtration
process, the maximum adsorption capacity is as high as 821 mg g–1, and the adsorption isotherms and kinetics obeyed
Langmuir isotherm and the pseudo-second-order kinetics models, respectively.
The anionic dye can also be separated from the mixture solution using
CO2-treated microgels. Moreover, a wastewater treatment
prototype with microgel-packed column was fabricated. Under continuous
flow condition, the dye was removed and recovered by alternative bubbling
CO2 and flushing with aqueous alkali (pH 12). Thus, this
type of microgels with CO2-induced protonation–deprotonation
transition can serve as a cost-effective, environmentally friendly,
and efficient adsorbent for water purification applications.
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