Browsing by Subject "Cross-linking"

Now showing 1 - 4 of 4

Open Access
Electrospinning of gelatin with tunable fiber morphology from round to flat/ribbon
(Elsevier, 2017) Topuz, F.; Uyar, T.
The electrospinning of gelatin with tunable fiber morphology from round to flat/ribbon was shown, and the detailed studies were conducted to correlate the fiber morphology with electrospinning process parameters and gelatin concentration in electrospinning solution. Particularly, variations in the applied voltage and the concentration of gelatin led to the transition of fiber shape from round to flat/ribbon. The formation of flat-shaped fibers was attributed to rapid evaporation of the solvent (formic acid) from the fiber matrix with increasing the applied voltage and gelatin concentration. On the other hand, round fibers were due to the steady evaporation of formic acid throughout the cross-section of fibers. WAXS analysis revealed that the loss of triple-helical crystalline structure in gelatin after the electrospinning process. The gelatin fibers were cross-linked through treatment with toluene 2,4-diisocyanate (TDI) in a mixed solution of acetone and pyridine, and XPS confirmed the cross-linking of the fibers over an increased carbon content on the elemental composition of the fiber surface due to the incorporated TDI moieties. Overall, this study focuses on morphological tuning of gelatin electrospun fibers towards a flat/ribbon-like structure by variation of electrospinning parameters and polymer concentration, and thus, the proposed concept can be adapted towards flattened/ribbon-like fibers of other protein-based systems by electrospinning.
Open Access
In situ-Electrochemically reduced graphene oxide integrated with cross-linked supramolecular polymeric network for electrocatalytic hydrogen evaluation reaction
(Elsevier, 2021-08-26) Aoudi, Bouthaina; Khaligh, Aisan; Sheidaei, Yasaman; Tuncel, Dönüş
Herein, we report the synthesis of a new supramolecular polymeric network (PCN) assembled through crosslinking of propyl bromide substituted tetraphenyl porphyrin with perhydroxy-cucurbit [8]uril and its use in the electrocatalytic hydrogen evaluation reaction after loading with nickel and integrating with in situ-electrochemically reduced graphene oxide (ERGO). Electrode was prepared by first coating graphene oxide on the FTO substrate followed by layering the nickel loaded PCN and finally by applying an appropriate voltage to reduce the graphene oxide in situ electrochemical reaction. The loading of nickel cocatalyst into PCN together with the integration of ERGO layer substantially improved its HER efficiency. Effect of various concentrations of Ni and GO on the HER activity of the developed electrocatalyst were investigated. Therein, ERGO1/Ni2@PCN catalyst containing 41% Ni and 50% GO (with respect to PCN) with only one layer of each component demonstrated excellent HER activity and stability with low onset and overpotentials of −20 mV, η@10 mA cm−2 of −360 mV, respectively, and remarkable hydrogen generation rate of 27.5 mmol h−1 g−1 in 1 M KOH. This noble-metal-free catalytic system is simple yet highly promising for the efficient hydrogen evolution reaction from water splitting.
Open Access
Synthesis and characterization of water dispersible conjugated polymer nanoparticles
(2011) İbrahimova, Vusala
In this study, novel water dispersible conjugated polymer nanoparticles having various potential applications in the areas including biomedicine and photonics have been synthesized from blue, green and yellow light emitting conjugated polymers. Their sizes, morphology, surface charges and optical properties have been determined using various techniques. Cell viability of nanoparticles was tested in mesenchymal stem cells. For the synthesis of nanoparticles, first the following polymers carrying a number of different functional groups and based on derivatives of fluorene and benzothiodiazole monomers are designed and synthesized using the Suzuki coupling reactions: Poly[(9,9-bis{propeny}fluorenyl-2,7-diyl)-co-(9,9-dihexyl-9H-fluorene)] (P1), poly[(9,9-bis{carboxymethylsulfonyl-propyl}fluorenyl-2,7-diyl)-co-(9,9-dihexyl-9Hfluorene) (P2), poly[(9,9- bis{propeny}fluorenyl-2,7-diyl))-co-(1,4-benzo-{2,1,3}- thiodiazole)] (P3), poly[(9,9- bis{carboxymethylsulfonyl-propyl}fluorenyl-2,7-diyl)- co(1,4-benzo-{2,1,3}-thiodiazole)] (P4), poly[(9,9-bis{3-bromopropyl}fluorenyl- 2,7-diyl)-co-(1,4-benzo-{2,1,3}-thiodiazole)] (P5), poly[(9,9-bis{3- azidopropyl}fluorenyl-2,7-diyl)-co-(benzothiadiazole)] (P6). Polymers were characterized by using spectroscopic techniques such as 1H-NMR, FT-IR, UV-Vis, Fluorescence spectrophotometer and Gel Permeation Chromatography (GPC). Conjugated polymers carry functional groups on their side chains, such as azide and allyl groups that can be cross-linkable using UV light to form shape-persistent, stable nanoparticles. Nanoparticles were characterized by various techniques before and after UV-treatment. Their sizes and morphologies were determined by using dynamic light scattering measurements (DLS) and imaging techniques such as scanning electron microscopy (SEM) and atomic force microscopy (AFM). For optical characterization UV-vis, fluorescent spectroscopies and FT-IR were used. CNPs affect on cells shows their nontoxic and biocompatible properties which give opportunity to use them in cell imaging.
Open Access
White emitting polyfluorene functionalized with azide hybridized on near-UV light emitting diode for high color rendering index
(Optical Society of America, 2008) Huyal, I. O.; Ozel, T.; Koldemir, U.; Nizamoglu, S.; Tuncel, D.; Demir, Hilmi Volkan
We develop and demonstrate high-quality white light generation that relies on the use of a single-type simple conjugated polymer of polyfluorene functionalized with azide groups (PFA) integrated on a near-UV LED platform. The high-quality white emission from the polyfluorene is achieved by using the azide functionalization to facilitate cross-linking intentionally when cast into solid-state form. Hybridized on n-UV InGaN/GaN LED at 378 nm, the PFA emitters collectively generate a very broad down-converting photoluminescence at longer wavelengths across the entirety of the visible spectrum, yielding high color rendering indices up to 91. (c) 2008 Optical Society of America.