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    Nanogel synthesis by irradiation of aqueous polymer solutions
    (Springer, 2021) Sütekin, S. Duygu; Güven, Olgun; Şahiner, Nurettin
    Nanogels/microgels are intramolecularly crosslinked particles with submicron diameters that can swell in a suitable solvent due to their three-dimensional network structure. Nanogels provide beneficial features such as flexibility, biocompatibility, high stability and swelling, fixed shape, large surface/volume ratio, fast stimuli-responsive behavior, etc. Therefore, there is growing interest to further elaborate nanogel formulations in preclinical applications as therapeutics, diagnostics, or nanosensors. However, conventional nanogel synthesis methods may end up with nanogels containing toxic residuals, e.g., initiator, crosslinking agent, and fragments which possess a major disadvantage in biomedical applications requiring tedious purification steps. This chapter reviews the synthesis of nanogels by irradiation of dilute aqueous polymer solutions to induce intramolecular crosslinking by gamma rays or accelerated electrons. This simple, ecofriendly, and cost-effective manufacturing method eliminates the purification step and provides the possibility to produce clean nanogels with desired sizes at room temperature. In the formation of nanogels, the degree of crosslinking can be controlled by polymer solution properties as well as operational parameters such as dose rate of radiation source and total absorbed dose. The method can be applied to many water-soluble polymers, copolymers, or interpolymer complexes for the development of nanogels with desired sizes and properties.
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    P(HMA-co-ATU) hydrogel synthesis via gamma radiation and its use for in situ metal nanoparticle preparation and as catalyst in 4-nitrophenol reduction
    (Pergamon-Elsevier Science Ltd, 2022) Güven, Olgun; Demirci, Şahin; Sütekin, S. Duygu; Ari, Betül; Şahiner, Nurettin
    Hydrogels with reactive thiourea functional groups were prepared by radiation-induced crosslinking of N-(Hydroxymethyl) acrylamide (HMA) and N-allyl thiourea (ATU) at different ATU content and irradiation doses. P (HMA-co-ATU) hydrogels were then utilized as template for in situ metal nanoparticle (MNP) preparation by the reduction of Ni2+, Co2+, and Cu(2+)ions within the hydrogel matrix using sodium borohydride (NaBH4) as reducing agent. These MNP@p(HMA-co-ATU) hydrogel composites (MNP = Co, Ni, and Cu) were further used as catalysts in the reduction reaction of 4-nitrophenol (4-NP) to 4-aminophenol (AP). Various parameters such as the effect of ATU content, the total dose used in the hydrogel preparation, MNPs type, and temperature on the catalytic activity of hydrogel composites were investigated. The activation energy, enthalpy, and entropy of Ni@p(HMA-co-ATU) hydrogels for the reduction reaction of 4-NP to 4-AP were calculated as 42.5 kJ mol-1, 38.9 kJ mol(-1), and-187.3 J mol(-1) K-1, respectively.
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    Tunable fluorescent and antimicrobial properties of poly(vinyl amine) affected by the acidic or basic hydrolysis of poly(N-vinylformamide)
    (Wiley, 2021) Demirci, Şahin; Kurt, Saliha B.; Güven, Olgun; Şahiner, Nurettin; Sütekin, S. Duygu
    Synthesis of poly(N-vinylformamide) (PNVF) and its subsequent hydrolysis toconvert it to poly(vinyl amine) (PVAm) were performed. Kinetics of acidic andbasic hydrolysis of poly(N-vinylformamide) (PNVF), and products of hydroly-sis were investigated by using Fourier transform infrared, size exclusion chro-matography,1H NMR, and13C NMR spectroscopies, and thermogravimetricanalysis. It was observed that amide groups did not completely transform intoamine groups by acidic hydrolysis of PNVF while the conversion of amidesinto amine groups via basic hydrolysis of PNVF was complete in 12 h, as con-firmed by spectroscopic measurements. Results of extensive characterizationrevealed significant structural and conformational differences between acidicand basic hydrolysis products. Fluorescence spectroscopy was used for the firsttime to follow the conversion of amide groups into amine groups. The fluores-cence intensity of PVAm obtained from basic hydrolysis of PVNF showed sig-nificant increase with amide/amine conversion. Finally, PVAm obtained fromacidic hydrolysis of PNVF demonstrated potent antimicrobial activity, 10–20times more, against common pathogens for example,C. albicans asfungalstrain andE. coli,S. aureus,B. subtilis,andP. aeruginosaas bacterial strains ascompared to PVAm obtained from basic hydrolysis.