Facile synthesis of 4-vinylpyridine-based hydrogels via laser-ignited frontal polymerization and their performance on ion removal

Continuous reactors of frontal polymerization in flow for the synthesis of polyacrylamide hydrogels with prescribed properties

Taking into account the fact that since the 1970s frontal polymerization (FP) reactors in flow have been the subject of our study, the work gives a brief chronology of the development of FP reactors for the synthesis of high molecular polymers, polymeric hydrogels with cross-linked structure, their advantages and drawbacks. The reasons for the impossibility of the practical implementation of tubular FP reactors in flow for the synthesis of polymers are established. The possibility of implementation of tubular FP reactors for the synthesis of polyacrylamide hydrogels (PAH) capable of absorbing and releasing large amount of water is presented. The paper also presents some data on the methods for the synthesis of PAHs with prescribed properties in tubular continuous FP reactors by way of using nano-additives and regulating the kinetics of the synthesis process. As a result, the synthesis process of PAHs with the required properties both in the absorption and release of water, and in the physical-mechanical properties was carried out in frontal tubular-type reactors in flow, and the water absorption kinetic curves and physical-mechanical properties of the obtained hydrogels are presented.

Early warning sensors for monitoring mercury in water

Poly-4-vinylpyridine grafted poly(vinylidene difluoride) (P4VP-g-PVDF) nanoporous polymer electrodes were found to be sensitive for Hg(II) analysis. The fabrication and characterization of functionalized nanoporous membrane-electrodes by FESEM and FTIR are presented. Functionalized nanopore charge state versus a large range of pH (1-10) was investigated by registering the streaming potential. This isoelectric point is achieved at the pKa of P4VP (pH = 5). Mercury adsorption at solid-liquid interface obeys a Langmuir law. A protocol for accurate Hg(II) analysis at ppb level was established. Calibration curves were performed and different real water samples (mineral water, ground water, surface water) were spiked and analyzed. The resulting sensor is intended to be integrated into existing systems or used standalone as portable devices. A first generation prototype exhibiting its own integrated potentiostat, its software and set of membrane-electrode pads is presented.

Rapid preparation of auto-healing gels with actuating behaviour

Gels with multiple stimuli-responsive actuating behaviour have shown great potential in many applications. Nevertheless, facile approaches to rapidly preparing gel actuators are still highly needed, and obtaining gels possessing both actuating and auto-healing capabilities remains a challenge. Herein, we report the rapid preparation of gel actuators with a self-healing ability. Dual-component gels, composed of poly(BA-co-VI-co-AM) (G-1) and poly(BA-co-AA-co-AM/β-CD) (G-2) (BA = butyl acrylate, VI = N-vinyl imidazole, AM = acrylamide, AA = acrylic acid, β-CD = β-cyclodextrin), are prepared within 10 minutes (min) via biphase frontal polymerization (FP). Both G-1 and G-2 gels show excellent intrinsic self-healing properties based on hydrogen bonds, with healing efficiencies of 91% and 97%, respectively; self-healing between G-1 and G-2 also occurs due to hydrogen bonding and host-guest interactions. Moreover, dual-component gels, in terms of G-1 and G-2 bilayer gel flowers and strips, heterogeneous healed bilayer gel strips, and microfluidic-directed bilayer gel microsphere ensembles, all show actuating behaviour in acidic, alkaline and organic solutions, with actuation degrees up to 96% in 5 min. The actuation mechanism is also proposed. This work might provide new insights into fast synthesis of self-healing dual-component gels towards application in the actuator field.

Generation of a carbon dots/ammonium persulfate redox initiator couple for free radical frontal polymerization

We report a new redox initiator couple of ammonium persulfate (APS)/carbon dots (CDs) with high initiation efficiency used in frontal polymerization (FP).

β-Cyclodextrin-based supramolecular poly(N-isopropylacrylamide) hydrogels prepared by frontal polymerization

Frontal polymerization (FP) was successfully applied to the synthesis of poly(N-isopropylacrylamide)-grafted-acryloyl-β-cyclodextrin supramolecularly crosslinked hydrogels. It was established that acryloyl-β-cyclodextrin (AβCD) allowed performing successful frontal polymerizations with N-isopropylacrylamide even in the absence of any covalent crosslinker, which is something generally required. It was found that the swelling properties of the resulting hydrogels can be tuned by varying the amount of AβCD. Namely, when little amounts of this non-covalent crosslinker were used, superabsorbent hydrogels were obtained. Hydrogels containing also a covalent crosslinker were also prepared for comparison. These latter exhibited swelling ratios that are much lower than the others.

Facile access to poly(DMAEMA-co-AA) hydrogels via infrared laser-ignited frontal polymerization and their polymerization in the horizontal direction

pH sensitive hydrogels are fabricated via infrared laser-ignited frontal polymerization (LIFP), and LIFP in the horizontal direction is employed towards dye adsorption.

In situ access to fluorescent dual-component polymers towards optoelectronic devices via inhomogeneous biphase frontal polymerization

Fluorescent dual-component poly(AM-co-NVP) and poly(HEA-co-NVP) polymers used to generate white LEDs were in situ synthesized via laser-ignited inhomogeneous biphase frontal polymerization.