دانلود رایگان مقاله تلفیق، شناسایی و الکتروریسی پلیمر پلی آنیلین پپتید جدید

Abstract

Aniline–peptide (FLDQV, FLDQVC, Dansyl-FLDQV, Dansyl-FLDQVC, and FLDQV-AMC) mixtures underwent oxidative chemical and electrochemical polymerization in excess of aniline. The products of the chemical polymerization were low molecular weight polymers containing more than 70% peptide. Electrochemically polymerized species polyaniline-FLDQV (PANI-FLDQV) consisted mainly of polyaniline units containing about 10% peptide. The solubility of the latter in 1,1,1,3,3,3-hexafluoro-2-propanol (HFP) was similar to the camphorsulfonic acid (CSA) doped emeraldine base (PANI-CSA) solubility, however the weight composition of the electrospun fibers produced from the two polymers was significantly different. 2D 1H–13C HSQC analyses were employed to analyze the binding between the aniline and peptide moieties. Binding of peptide to polyaniline is reflected by the appearance of extra cross-peaks which display line broadening between the free polyaniline and the free pentapeptide. Peptides may be chemically bonded to the polymer molecules, but they may also act as doping agents to the nitrogen atoms via hydrogen bonding.

3. Results and discussion

The absorption and emission spectra of the peptides and polymerization products were collected in N-methyl pyrollidinone (NMP) which has an optical cut-off at 285 nm. The spectra are shown in Figs. 1 and 2. Dansyl-FLDQVC peptide exhibits a broad absorption band at 346 nm. Two absorption bands were observed in the spectrum of the polymerized product. The long-wavelength absorption maximum undergoes slight hypsochomic shift (max 338 nm) and a new absorption band appears at 306 nm. The former is due to the presence of the dansyl chromophore, while the latter can be assigned to the–* transitions ofthe polyaniline backbone. It is possible that polyaniline has another absorption transition Solid state 1H NMR spectra indicated presence of significant amount of peptide in the chemically polymerized product. The latter was quantified using absorption and emission spectra. Standard curves were constructed from serial dilutions from 0.05 mg/mL to 0.35 mg/mL for Dansyl FLDQVC and 0.02–0.14 mg/mL for FLDQVAMC. The amount of peptide in the polymer varied between 70 and 80% for the different peptides used in the experiment. Fig. 3 shows the electrochemical growth of aniline and anilineFLDQV in 0.1 M HCl. First anodic peak corresponds to the oxidation of monomer and reduction peak appears which shows that the formation of polymer on electrode surface. The subsequent swipes show three anodic oxidation peaks corresponding to the three different oxidationstates of polyaniline (leucoemeraldine, emeraldine andpernigraniline). The current values of eachoxidationandreduction peaks are greater than that of a previous cycle which indicates that the polymer thickness is increasing on the electrode surface. The peak potentials slightly shift as the film becomes thicker due to a decrease in electrical conductivity and increase in conjugation length. The effect of an increasing concentration of FLDQV on the voltamograms is presented in Fig. 3. No significant qualitative difference is observed until the 40 mg FLDQV sample other then expected decrease in the current values.