Decomposition kinetics of polymer-nanocomposite materials

The synthesis of polythiophenes functionalized with an alkyl group such as coumarin and naphthol were performed successfully. A previously - described technique of WS2 synthesis from thiourea and tungstic acid was utilized to synthesize exfoliated WS2, which was employed to synthesize nanocomposite materials. Also, novel exfoliated polythiophene and poly(3-alkylthiophene) with naphthol nanocomposites using various percentages of tungsten disulfide were prepared using in-situ polymerization of the monomer with iron (III) chloride in the presence of exfoliated WS2. Additionally, the exfoliated nanocomposites of polyaniline were synthesized by an in-situ polymerization reaction of aniline with ammonium peroxydisulfate in the presence of exfoliated WS2. The poly(3-alkylthiophene) decorated with naphthol was characterized by using techniques such as NMR, FTIR, and TGA. These techniques were utilized to determine the difference between the monomers and their polymers. Both polymers displayed a noticeable improvement in thermal stability. The exfoliated nanocomposites of PThN-WS2 were also characterized using techniques such as FT-IR and XRD.The results obtained suggest that there is an interaction between the polymer and the WS2 due to the vibrational change in the IR spectrum. Ozawa's method was applied to determine the decomposition kinetics of these exfoliated nanocomposites using the Thermogravimetric Analysis (TGA). The activation energies for PTh and their six different compositions of WS2 were measured under air. Each sample was studied using four selected heating rates: 5, 10, 20 and 40 o C/min. The similar procedures were followed to compute Ea for PThN-WS2 nanocomposites. The results demonstrated that the incorporation of nanofillers has improved the Ea value for PTh-WS2 and PThN-WS2 nanocomposites. It was found that the presence of alkyl group (naphthol) on the thiophene ring has enhanced the Ea by approximately 65 kJ/mol compared to pure PTh with around 79.9 kJ/mol. Furthermore, the values of the Ea for exfoliated PT-WS2 and PThN-WS2 compositions were increased by incorporating higher percents of WS2 in comparison to that of pure PT or PThN. Ozawa's method was also applied to determine the activation energies for the pure polyaniline and their nanocomposites with WS2. All experiments were carried out in a TGA at four different heating rates under a nitrogen atmosphere. It was demonstrated that the incorporation of exfoliated WS2 in polyaniline showed an enhancement in the Ea values. Also, 12.5% of WS2-PANI composition recorded the highest Ea with 165 kJ/mol compared to that of Ea of pristine PANI with 129.8 kJ/mol.