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. 2017 Nov 16;9(11):626.
doi: 10.3390/polym9110626.

From Insulating PMMA Polymer to Conjugated Double Bond Behavior: Green Chemistry as a Novel Approach to Fabricate Small Band Gap Polymers

Shujahadeen B Aziz  1   2 , Omed Gh Abdullah  3   4 , Ahang M Hussein  5 , Hameed M Ahmed  6
Affiliations

From Insulating PMMA Polymer to Conjugated Double Bond Behavior: Green Chemistry as a Novel Approach to Fabricate Small Band Gap Polymers

Shujahadeen B Aziz et al. Polymers (Basel). .

Abstract

Dye-doped polymer films of Poly(methyl methacrylate) PMMA have been prepared with the use of the conventional solution cast technique. Natural dye has been extracted from environmentally friendly material of green tea (GT) leaves. Obvious Fourier transform infrared (FTIR) spectra for the GT extract were observed, showing absorption bands at 3401 cm-1, 1628 cm-1, and 1029 cm-1, corresponding to O⁻H/N⁻H, C=O, and C⁻O groups, respectively. The shift and decrease in the intensity of the FTIR bands in the doped PMMA sample have been investigated to confirm the complex formation between the GT dye and PMMA polymer. Different types of electronic transition could be seen in the absorption spectra of the dye-doped samples. For the PMMA sample incorporated with 28 mL of GT dye, distinguishable intense peak around 670 nm appeared, which opens new frontiers in the green chemistry field that are particularly suitable for laser technology and optoelectronic applications. The main result of this study showed that the doping of the PMMA polymer with green tea dye exhibited a strong absorption peak around 670 nm in the visible range. The absorption edge was found to be shifted towards the lower photon energy for the doped samples. Optical dielectric loss and Tauc's model were used to estimate the optical band gaps of the samples and to specify the transition types between the valence band (VB) and conduction band (CB), respectively. A small band gap of around 2.6 eV for the dye-doped PMMA films was observed. From the scientific and engineering viewpoints, this topic has been found to be very important and relevant. The amorphous nature of the doped samples was found and ascribed to the increase of Urbach energy. The Urbach energy has been correlated to the analysis of X-ray diffraction (XRD) to display the structure-properties relationships.

Keywords: FTIR study; Urbach energy; XRD study; band gap analysis; dye doped polymer; extract GT solution.

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Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1
Flowchart of the experimental method and characterization techniques.
Figure 2
Figure 2
Fourier transform infrared (FTIR) spectra of pure green tea (GT) extract.
Figure 3
Figure 3
FTIR spectra of pure PMMA polymer (GT 0). It is obvious that the peaks are sharp and their intensity is high.
Figure 4
Figure 4
FTIR spectra of dye doped PMMA polymer (GT 28). Shifting of peaks and their broadening is evidence for the complex formation between the extract GT solution and PMMA polymer.
Figure 5
Figure 5
The absorption spectra of pure PMMA and PMMA doped samples.
Figure 6
Figure 6
The absorption spectra of pure PMMA and PMMA doped samples at longer wavelengths.
Figure 7
Figure 7
The absorption coefficients versus photon energy for pure PMMA and PMMA doped samples.
Figure 8
Figure 8
The plots of (αhυ)2 vs. (hυ) for all the samples.
Figure 9
Figure 9
The plots of (αhυ)1/2 vs. (hυ) for all the samples.
Figure 10
Figure 10
The plots of (αhυ)2/3 vs. (hυ) for all the samples.
Figure 11
Figure 11
Optical dielectric loss spectra for pure and doped PMMA samples.
Figure 12
Figure 12
Urbach plot for pure PMMA (GT 0) and PMMA doped (GT 28) samples.
Figure 13
Figure 13
XRD pattern of pure PMMA (GT0) and PMMA doped sample (GT28).
See this image and copyright information in PMC

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