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. 2023 Sep 29;15(19):3934.
doi: 10.3390/polym15193934.

Thermal Degradation Studies of Poly(2-ethyl hexyl acrylate) in the Presence of Nematic Liquid Crystals

Amina Bouriche  1   2 , Lamia Alachaher-Bedjaoui  1 , Ana Barrera  2 , Jean-Noël Staelens  2 , Ulrich Maschke  2
Affiliations

Thermal Degradation Studies of Poly(2-ethyl hexyl acrylate) in the Presence of Nematic Liquid Crystals

Amina Bouriche et al. Polymers (Basel). .

Abstract

The thermal degradation behavior of Poly(2-ethyl hexyl hcrylate) (Poly(2-EHA)), blended with a commercially available nematic liquid crystal (LC) mixture, was investigated by thermal gravimetric analysis (TGA). Different heating rates, ranging from 5 to 200 °C/min, were applied under an inert atmosphere. Based on the TGA results, activation energies (Eα) at different conversion rates (α) were determined using three integral isoconversion methods: Flynn-Wall-Ozawa (FWO), Tang, and Kissinger-Akahira-Sunose (KAS). It can be noticed that the global evolution of these activation energies was the same for the three models. The coefficient of determination R2 presented values generally higher than 0.97. Using these models, the Eα value for the LC remains constant at 64 kJ/mol for all conversions rates. For the polymer Poly(2-EHA), applying the Tang and FWO models, the activation energy presents a variation ranging from 80 kJ/mol, for conversion α = 0.1, to 170 kJ/mol, for α = 0.9. For the third model (KAS), this energy varies between 80 and 220 kJ/mol in the same range of α.

Keywords: liquid crystal; non-isothermal method; polymer; thermal stability; thermogravimetric analysis.

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Conflict of interest statement

The authors declare that they have no known competing financial interest or personal relationships that could have appeared to influence the work reported in this paper.

Figures

Figure 1
Figure 1
Chemical structures of (a) Poly 2-EHA and (b) E7.
Figure 2
Figure 2
Thermograms presenting (a) the weight losses and (b) their derivatives as a function of temperature for the LC E7, at different heating rates.
Figure 3
Figure 3
Thermograms presenting (a) the weight losses and (b) their derivatives as a function of temperature for Poly(2-EHA), at different heating rates.
Figure 4
Figure 4
Thermograms presenting (a) the weight losses and (b) their derivatives as functions of temperature and composition for Poly(2-EHA)/E7 mixtures (heating rate: 10 °C/min).
Figure 4
Figure 4
Thermograms presenting (a) the weight losses and (b) their derivatives as functions of temperature and composition for Poly(2-EHA)/E7 mixtures (heating rate: 10 °C/min).
Figure 5
Figure 5
Texture of Poly-2 EHA/E7 samples at different concentrations observed at 58 °C in the nematic + isotropic state: (a) 30 wt-% E7, (b) 40 wt-% E7, (c) 60 wt-% E7, (d) 70 wt-% E7, (e) 80 wt-% E7, and (f) 90 wt-% E7.
Figure 6
Figure 6
Ln(β/T1.894661) as function of 1/T for Poly(2-EHA)/E7 mixtures, according to the conversion α, using the approach of Tang et al. (a) 100 wt-% E7, (b) 95 wt-% E7, (c) 80 wt-% E7, (d) 50 wt-% E7, (e) 20 wt-% E7 and (f) Poly(2-EHA).
Figure 7
Figure 7
Ln(β) as function of 1/T for Poly(2-EHA)/E7 mixtures, according to the conversion α, applying the approach of FWO et al. (a) 100 wt-% E7, (b) 95 wt-% E7, (c) 80 wt-% E7, (d) 50 wt-% E7, (e) 20 wt-% E7 and (f) Poly(2-EHA).
Figure 8
Figure 8
Ln(β/T2) as function of 1/T for Poly(2-EHA)/E7 mixtures, according to the conversion α, using the approach of KAS et al. [63]. (a) 100 wt-% E7, (b) 95 wt-% E7, (c) 80 wt-% E7, (d) 50 wt-% E7, (e) 20 wt-% E7 and (f) Poly(2-EHA).
Figure 9
Figure 9
Variation of the apparent activation energies of E7 and Poly(2-EHA) and their mixtures according to the conversion α: (a) Tang model, (b) FWO model and (c) KAS model.
Figure 9
Figure 9
Variation of the apparent activation energies of E7 and Poly(2-EHA) and their mixtures according to the conversion α: (a) Tang model, (b) FWO model and (c) KAS model.
Figure 10
Figure 10
Dependence of Eα on conversion α for E7, evaluated by Tang, FWO and KAS methods.
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