Browsing by Subject "Polyamides"

Now showing 1 - 7 of 7

Open Access
A conducting composite of polypyrrole II. As a gas sensor
(Elsevier, 1995) Selampinar, F.; Toppare, L.; Akbulut, U.; Yalçin, T.; Süzer, Ş.
Pure polypyrrole (PPy) and polypyrrole-polyamide (PPy-PA) composite films were synthesized electrochemically. The gas-sensing ability was investigated for both pure PPy and PPy-PA films. The composite films' response to several gases are better defined and reproducible compared to pristine conducting polymer. Electrochemical behaviour of PPy and PPy-PA electrodes in the presence of pyrrole and pyrrole-free medium is investigated via cyclic voltammetry. Mass spectrometry studies strictly reveal that the composite is completely different to a mechanical mixture. This phenomenon is discussed in comparison to polyaniline-polycarbonate composite. © 1995.
Open Access
Electrospun nylon 6,6 nanofibers functionalized with cyclodextrins for removal of toluene vapor
(John Wiley and Sons Inc., 2015) Kayaci, F.; Sen, H. S.; Durgun, Engin; Uyar, Tamer
Functional nylon 6,6 nanofibers incorporating cyclodextrins (CD) were developed via electrospinning. Enhanced thermal stability of the nylon 6,6/CD nanofibers was observed due to interaction between CD and nylon 6,6. X-ray photoelectron spectroscopy and attenuated total reflectance Fourier transform infrared spectroscopy studies indicated the existence of some CD molecules on the surface of the nanofibers. Electrospun nylon 6,6 nanofibers without having CD were ineffective for entrapment of toluene vapor from the environment, whereas nylon 6,6/CD nanofibrous membranes can effectively entrap toluene vapor from the surrounding by taking advantage of the high surface-volume ratio of nanofibers with the added advantage of inclusion complexation capability of CD presenting on the nanofiber surface. The modeling studies for formation of inclusion complex between CD and toluene were also performed by using ab initio techniques. Our results suggest that nylon 6,6/CD nanofibrous membranes may have potential to be used as air filters for the removal of organic vapor waste from surroundings.
Open Access
Fluorescent Si QD decoration onto a flexible polymeric electrospun nanofibrous mat for the colorimetric sensing of TNT
(Royal Society of Chemistry, 2017) Arslan, O.; Aytac Z.; Uyar, Tamer
UV range light was used for the facile, effective and large-scale synthesis of visible light emitting, surface-protected silicon quantum dots (Si QDs) starting from an amine-functionalized alkoxy silane precursor. Within mild and easy hydrolysis/condensation environments, the use of an amine-functionalized precursor together with a reducing agent resulted in a bright visible green light that could be used for fluorescent analytical detection systems. Visible light emitting Si QDs were investigated and it was found that their emission character depends on the illumination time, hydrolysis/condensation conditions and pretreatments for the silane coupling agents. A Nylon 6,6 electrospun nanofibrous mat was selected as a substrate for decoration by the Si QDs in order to fabricate a flexible and free-standing polymeric nanofibrous mat posessing a visible light emitting character so that it could act as a visible colorimetric sensor. The visible light emitting Si QDs were decorated onto the Nylon 6,6 nanofibrous mats via covering the surfaces as a ‘nanodress’ by a simple impregnation/dip-coating and heat-curing methods. The analytical results revealed that the Si QDs decorated flexible polymeric nanofibrous mats could be utilized for colorimetric trinitrotoluene (TNT) detection in low concentrations.
Open Access
Multifunctional electrospun polymeric nanofibrous mats for catalytic reduction, photocatalysis and sensing
(Royal Society of Chemistry, 2017) Arslan, O.; Uyar, Tamer
Fabrication and decoration of flexible Nylon 6,6 polymeric nanofibrous mats for production of multifunctional electrospun material was accomplished via visible light-emitting surface-protected silicon quantum dots (Si QD), ZnO nanoparticles (ZnO NP) and Pd nanocubes (Pd NC). UV-range light was utilized for Si QD production and, after hydrolysis/condensation together with nucleation and growth reactions, amine-modified, fluorescent Si QD were obtained. Additionally, available molecular groups on the Si QD coated onto the polymeric nanofibrous mats provided further attachment of metal oxide and metal NP for various catalytic purposes. Analytical investigations showed that visible-light emission could be maintained on the Nylon 6,6 mats for trinitrotoluene (TNT) sensing. Also, due to consecutive NP decoration, multifunctional, polymeric, flexible nanofibrous mats were obtained. Experiments revealed that fabricated multifunctional mats could reduce molecules such as paranitrophenol effectively or decompose waste dyes such as methylene blue via photocatalytic experiments, and sense the pollutant TNT in aqueous solutions as an all-in-one concept.
Open Access
On the possibility of grafting conducting polymers into insulating ones
(Elsevier, 1996) Bahçeci, S.; Toppare, L.; Yurtsever, E.
The possibility of grafting between conducting polymers, like polypyrrole (PPy) and polyaniline (PAn), and insulating polymers, such as polybisphenol A carbonate (PC) and polyamide (PA), is studied via semi-empirical methods using the AM1 parametrization. Several experimental studies on the issue have previously revealed that a chemical interaction exists between the couples (PAn-PC, PPy-PC and PPy-PA) during the electrochemical synthesis of PAn and PPy in the insulating host matrices. Here we present additional theoretical evidence indicating that such grafting is possible, at least for small oligomers.
Open Access
Single-site mutation and secondary structure stability: an isodesmic reaction approach. The case of unnatural amino acid mutagenesis Ala→Lac
(American Chemical Society, 2004) Cieplak, A. S.; Sürmeli, N. B.
A method is described to evaluate backbone interactions in proteins via computational unnatural amino acid mutagenesis. Several N-acetyl polyalanyl amides (AcA nNH 2) were optimized in the representative helical (3 10-, 4 13-, and a "hybrid" κ-helix, n = 7, 9, 10, 14) and hairpin (two- and three-stranded antiparallel β-sheets with type I turns βααε, n =6, 9, 10) conformations, and extended conformers of N-acetyl polyalanyl methylamides (n = 2, 3) were used to derive multistranded β-sheet fragments. Subsequently, each residue of every model structure was substituted, one at a time, with L-lactic acid. The resulting mutant structures were again optimized, and group-transfer energies ΔE GT were obtained as heats of the isodesmic reactions: AcA nNHR + AcOMe → AcA xLacA yNHR + AcNHMe (R = H, C H 3). These group-transfer energies correlate with the degree of charge polarization of the substituted peptide linkages as measured by the difference Δe in H and O Mulliken populations in HN-C=O and with the H-bond distances in the "wild-type" structures. A good correlation obtains for the HF/3-21G and B3LYP/6-31G* group-transfer energies. The destabilization effects are interpreted in terms of loss of interstrand and intrastrand H-bonds, decrease in Lewis basicity of the C-O group, and O⋯O repulsion. On the basis of several comparisons of Ala → Lac ΔE GT's with heats of the NH → CH 2 substitutions, the latter contribution is estimated (B3LYP/6-31G*) to range between 1.5 and 2.4 kcal mol -1, a figure close to the recent experimental ΔδG° value of 2.6 kcal mol -1 (McComas, C. C.; Crowley, B. M.; Boger, D. L. J. Am. Chem. Soc. 2003, 125, 9314). The partitioning yields the following maximum values of the electronic association energy of H-bonds in the examined sample of model structures (B3LYP/6-31G* estimates): 3 10-helix D e = -1.7 kcal mol -1, α-helix D e = -3.8 kcal mol -1 β-sheet D e = -6.1 kcal mol -1. The premise of experimental evaluations of the backbone-backbone H-bonding that Ala → Lac substitution in proteins is isosteric (e.g., Koh, J. T.; Cornish, V. W.; Schultz, P. G. Biochemistry 1997, 36, 11314) is often but not always corroborated. Examination of the integrity of H-bonding pattern and ψ i, ψ i distribution identified several mutants with significant distortions of the "wild-type" structure resulting inter alia from the transitions between i, i + 3 and i, i + 4 H-bonding in helices, observed previously in the crystallographic studies of depsipeptides, (Ohyama, T.; Oku, H.; Hiroki, A.; Maekawa, Y.; Yoshida, M.; Katakai, R. Biopolymers 2000, 54, 875; Karle, I. L.; Das, C.; Balaram, P. Biopolymers 2001, 59, 276). Thus, the isodesmic reaction approach provides a simple way to gauge how conformation of the polypeptide chain and dimensions of the H-bonding network affect the strength of backbone-backbone C=O⋯HN bonds. The results indicate that the stabilization provided by such interactions increases on going from 3 10-helix to α-helix to β-sheet.
Open Access
X-ray photoelectron spectroscopic investigation of conducting polymer blends
(Springer, 1996) Süzer, Ş.; Toppare, L.; Hallam, K. R.; Allen, G. C.
Electrochemically prepared films of conducting polymers of polypyrrole and polythiophene and their blends with polyamide have been investigated by X-ray photoelectron spectroscopy. In the N1s region of the spectra of films containing polypyrrole the peak corresponding to N+ at 402.0 eV is separated from that of neutral N. The intensity of the N+ peak can be correlated with the electrical conductivity of the films and the spectroscopically derived ratio of F/N+ is close to 4 indicating that one BF4 - dopant ion is incorporated for every oxidized nitrogen center. In the spectra of films of polythiophene and its blends peaks corresponding to S and S+ can not be resolved but again the F/C ratio correlates with the electrical conductivity. © Springer-Verlag 1996.