pH and Thermo Sensitive Superabsorbent Poly (N-Hydroxymethylacrylamide-co-Itaconic Acid) Hydrogels: Synthesis, Characterization and Kinetic Studies

Nonconjugated Biocompatible Macromolecular Luminogens for Sensing and Removals of Fe(III) and Cu(II): DFT Studies on Selective Coordination(s) and On-Off Sensing

This work reports the design and synthesis of two nonaromatic biocompatible macromolecular luminogens, i.e., 2-(dimethylamino)ethyl methacrylate-co-2-(dimethylamino)ethyl 3-(N-(methylol)acrylamido)-2-methylpropanoate-co-N-(methylol)acrylamide/DMAEMA-co-DMAENMAMP-co-NMA (P1) and methacrylic acid-co-3-(N-(methylol)acrylamido)-2-methylpropanoic acid-co-N-(methylol)acrylamide/MEA-co-NMAMPA-co-NMA (P2), prepared through in situ anchored acrylamido-ester/DMAENMAMP and acrylamido-acid/NMAMPA third comonomers, respectively, in a facile polymerization of two non-luminous monomers in water medium to circumvent the drawbacks related to aggregation-caused quenching of aromatic luminogens. The structures of P1/P2, in situ anchored comonomers, fluorophores, N-branching associated n-π* interactions, and hydrogen bonding assisted aggregation-enhanced emissions are comprehended by nuclear magnetic resonance, Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), ultraviolet-visible, thermogravimetric analysis (TGA), dynamic light scattering (DLS), transmission electron microscopy (TEM), fluorescence lifetime, and fluorescence imaging. P1 and P2 are appropriate for sensitive detections/exclusions of Fe(III)/Cu(II) and cell-imaging. The intrinsic fluorescence, on-off sensing, selective coordinations of Fe(III) and Cu(II) with fluorophores, emission quenching mechanisms, and removals of Fe(III) and Cu(II) are investigated by DFT/NTO analyses of P1/P2 and Fe(III)-P1 and Cu(II)-P2 complexes, XPS, and isotherms and kinetics parameters. The excellent biocompatibilities, comparable limit of detections, i.e., 1.70 × 10^-7 and 1.59 × 10^-7 [m], and higher adsorption capacities, i.e., 77.25 and 154.13 mg g^-1 , at low ppm; 303 K; and pH = 7 compel P1/P2 to be acceptable for multipurpose applications.

Swelling behavior of poly (N-hydroxymethylacrylamide-co-acrylic acid) hydrogels and release of potassium nitrate as fertilizer

Poly (N-hydroxymethylacrylamide-co-acrylic acid) [P(NHMA-AAx)] hydrogels were prepared by free-radical polymerization in aqueous solution at 56°C, using N,N′-methylenebisacrylamide as the cross-linking agent. The synthesized hydrogels were subsequently investigated by a series of characterization techniques including Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis and differential scanning calorimetry analysis. The effects of comonomer composition in the feed, pH, temperature and ionic strength on the swelling behavior were studied. Results indicated that the swelling capabilities of P(NHMA-AAx) hydrogels decreased with the increase in N-hydroxymethylacrylamide (NHMA) content in the polymeric matrix and ionic strength of the medium. Additionally, the hydrogels showed both temperature and pH responses. The dynamic swelling behaviors of hydrogels at different pH values followed a non-Fickian type. The P(NHMA-AAx) hydrogels were also loaded with potassium nitrate (KNO3) as a model agrochemical, and the release kinetics of fertilizer from the hydrogels was studied as a function of KNO3 and NHMA concentrations. Moreover, various kinetic parameters, such as release exponents and diffusion coefficients, were calculated.