Browsing by Author "Besenbacher, F."

Now showing 1 - 7 of 7

Open Access
Characterisation of internal morphologies in electrospun fibers by X-ray tomographic microscopy
(Royal Society of Chemistry, 2011) Nygaard, J. V.; Uyar, Tamer; Chen, M.; Cloetens, P.; Kingshott, P.; Besenbacher, F.
Electrospun fabrics for use in, for example, tissue engineering, wound dressings, textiles, filters and membranes have attracted a lot of attention due to their morphological nanoscale architectures which enhance their physical properties. A thorough detailed internal morphological study has been performed on electrospun polystyrene (PS) fibers produced from dimethylformamide (DMF) solutions. Investigations by transmission electron microscopy (TEM) and thorough studies for the first time by synchrotron based X-ray tomographic microscopy (XTM) revealed that the individual electrospun PS fibers and beads have a graded density and in some cases even an internal porous structure. © The Royal Society of Chemistry 2011.
Open Access
Cyclodextrin functionalized poly(methyl methacrylate) (PMMA) electrospun nanofibers for organic vapors waste treatment
(Elsevier BV, 2010) Uyar, Tamer; Havelund, R.; Nur, Y.; Balan, A.; Hacaloglu, J.; Toppare, L.; Besenbacher, F.; Kingshott, P.
Poly(methyl methacrylate) (PMMA) nanofibers containing the inclusion complex forming betacyclodextrin (_-CD) were successfully produced by means of electrospinning in order to develop functional nanofibrous webs for organic vapor waste treatment. Electrospinning of uniform PMMA nanofibers containing different loadings of _-CD (10%, 25% and 50% (w/w)) was achieved. The surface sensitive spectroscopic techniques; X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) showed that some of the _-CD molecules are present on the surface of the PMMA nanofibers, which is essential for the trapping of organic vapors by inclusion complexation. Direct pyrolysis mass spectrometry (DP-MS) studies showed that PMMA nanowebs containing _-CD can entrap organic vapors such as aniline, styrene and toluene from the surroundings due to inclusion complexation with _-CD that is present on the fiber surface. Our study showed that electrospun nanowebs functionalized with cyclodextrinsmayhave the potential to be used as molecular filters and/or nanofilters for the treatment of organic vapor waste and air filtration purposes.
Open Access
Electrospinning of functional poly(methyl methacrylate) nanofibers containing cyclodextrin-menthol inclusion complexes
(Institute of Physics Publishing, 2009) Uyar, Tamer; Nur, Y.; Hacaloglu, J.; Besenbacher, F.
Electrospinning of nanofibers with cyclodextrin inclusion complexes (CD-ICs) is particularly attractive since distinct properties can be obtained by combining the nanofibers with specific functions of the CD-ICs. Here we report on the electrospinning of poly(methyl methacrylate) (PMMA) nanofibers containing cyclodextrin-menthol inclusion complexes (CD-menthol-ICs). These CD-menthol-IC functionalized nanofibers were developed with the purpose of producing functional nanofibers that contain fragrances/flavors with high temperature stability, and menthol was used as a model fragrance/flavor material. The PMMA nanofibers were electrospun with CD-menthol-ICs using three type of CD: α-CD, β-CD, and γ-CD. Direct pyrolysis mass spectrometry (DP-MS) studies showed that the thermal evaporation of menthol occurred over a very high and a broad temperature range (100-355 °C) for PMMA/CDmenthol-IC nanowebs, demonstrating the complexation of menthol with the CD cavity and its high temperature stability. Furthermore, as the size of CD cavity increased in the order α-CD<β-CD<γ-CD, the thermal evolution of menthol shifted to higher temperatures, suggesting that the strength of interaction between menthol and the CD cavity is in the order γ-CD>β-CD>α-CD. © 2009 IOP Publishing Ltd.
Open Access
Electrospun polyethylene oxide (PEO) nanofibers containing cyclodextrin inclusion complex
(American Scientific Publishers, 2011) Uyar, Tamer; Hacaloglu, J.; Besenbacher, F.
In this study, we obtained functional electrospun nanofibers containing stable fragrance/flavor molecule facilitated by cyclodextrin inclusion complexation. Menthol was used as a model fragrance/flavor molecule and we have electrospun poly(ethylene oxide) (PEO) nanofibers containing cyclodextrin-menthol inclusion complexes (CD-menthol-IC). We used two different solvent systems; water and water:ethanol and three types of CDs; α-CD, β-CD and γ-CD in order to find the optimal performance for the stabilization of menthol at high temperatures. We observed that the solvent system used for electrospinning process and the types of CDs (α-CD, β-CD and γ-CD) are very important to obtain CD-menthol-IC which ultimately determines the durability and temperature stability of menthol in the PEO nanofibrous web. We found out that it is better to use water rather than the water:ethanol solvent system for the inclusion complexation and additionally β-CD and γ-CD are most favorable choices since they are able to form complexation with menthol in the water solvent system. Despite the high volatility nature of menthol, our results demonstrated that the stability and temperature release of menthol was sustained to a very high and a broad temperature range (100 °C-250 °C) for PEO nanowebs containing CD-menthol-IC whereas the PEO nanofibers without CD and without CD-menthol complex could not preserve menthol even during storage. In brief, the results are very encouraging and open up for a variety of new exciting possibilities for the development of multi-functional electrospun nanofibers containing cyclodextrin inclusion complexes. Copyright © 2011 American Scientific Publishers All rights reserved.
Open Access
Electrospun UV-responsive supramolecular nanofibers from a cyclodextrin-azobenzene inclusion complex
(Royal Society of Chemistry, 2013) Chen, M.; Nielsen, S. R.; Uyar, Tamer; Zhang, S.; Zafar, A.; Dong, M.; Besenbacher, F.
A combination of the unique hosting properties of cyclodextrins (CDs) and the peculiar UV-responsive trans-cis isomerization of the guest molecule azobenzene has endowed light-responsibility of the inclusion complex (IC). The IC of 4-aminoazobenzene (AAB) and hydroxypropyl-β-cyclodextrin (HPβCD), with its inherent viscosity from hydrogen bondings between CDs and π-π stacking between AABs, was electrospun into nanofibers from water without using any carrier polymer matrix. The integrity of electrospun ICs was proven by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), together with Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The homogeneous distribution of HPβCD-AAB-IC was confirmed by surface chemistry mapping using time-of-flight secondary ion mass spectrometry (ToF-SIMS). The UV response of ICs prior to, during and post electrospinning was investigated. UV irradiation prior to electrospinning caused precipitation of AAB from the aqueous IC solution. UV irradiation during electrospinning flight demonstrated the interruption of ICs and consequently broader diameter distributions were obtained. Post-spinning UV irradiation induced topography and adhesion force changes on the electrospun nanofiber surfaces, demonstrated by in situ atomic force microspectroscopy (AFM) quantitative nanomechanical mapping. The present study is the first case where the supramolecule with stimuli response was electrospun into nanofibers with retained activity. © 2013 The Royal Society of Chemistry.
Open Access
Functional electrospun polystyrene nanofibers incorporating α-, β-, and γ-cyclodextrins: Comparison of molecular filter performance
(2010) Uyar, Tamer; Havelund, R.; Hacaloglu, J.; Besenbacher, F.; Kingshott, P.
Electrospinning has been used to successfully create polystyrene (PS) nanofibers containing either of three different types of cyclodextrin (CD); α-CD, β-CD, and γ-CD. These three CDs are chosen because they have different sized cavities that potentially allow for selective inclusion complex (IC) formation with molecules of different size or differences in affinity of IC formation with one type of molecule. The CD containing electrospun PS nanofibers (PS/CD) were initially characterized by scanning electron microscopy (SEM) to determine the uniformity of the fibers and their fiber diameter distributions. X-ray photoelectron spectroscopy (XPS) was used to quantitatively determine the concentration of each CD on the different fiber surfaces. Static time-of-flight secondary ion mass spectrometry (static-ToF-SIMS) showed the presence of each type of CD on the PS nanofibers by the detection of both the CD sodium adduct molecular ions (M + Na+) and lower molecular weight oxygen containing fragment ions. The comparative efficiency of the PS/CD nanofibers/nanoweb for removing phenolphthalein, a model organic compound, from solution was determined by UV-vis spectrometry, and the kinetics of phenolphthalein capture was shown to follow the trend PS/α-CD > PS/β-CD > PS/γ-CD. Direct pyrolysis mass spectrometry (DP-MS) was also performed to ascertain the relative binding strengths of the phenolphthalein for the CD cavities, and the results showed the trend in the interaction strength was β-CD > γ-CD > α-CD. Our results demonstrate that nanofibers produced by electrospinning that incorporate cyclodextrins with different sized cavities can indeed filter organic molecules and can potentially be used for filtration, purification, and/or separation processes. © 2010 American Chemical Society.
Open Access
Self-aligned and bundled electrospun fibers prepared from blends of polystyrene (PS) and poly(methyl methacrylate) (PMMA) with a hairt-rod polyphenylene copolymer
(Elsevier, 2009-07-31) Uyar, Tamer; Cianga, I.; Cianga, L.; Besenbacher, F.; Yagci, Y.
Bundled and self-aligned fibers were obtained by electrospinning blends of polystyrene (PS) and poly (methyl methacrylate) (PMMA) with a hairy-rod polyphenylene-g-polystyrene/poly (a-caprolactone) (PP-g-PS/PCL) copolymer. The self-alignment and bundling characteristics of these electrospun fibers were ascribed to the unique molecular architecture of the conjugated polymer, PP-g-PS/PCL, and its interactions with the solvent and the polymer matrixes used for the electrospinning. The self-alignment and bundling was found to be much more pronounced for PP-g-PS/PCL-PS blend when compared to PP-g-PS/PCL-PMMA blend. Furthermore we found that the degree of self-alignment of the fiber bundles was enhanced by increasing the amount of PP-g-PS/PCL in the blends but the alignment completely disappeared when the solvent dimethylformamide was changed to chloroform.