Comparative Kinetic Study and Microwaves Non-Thermal Effects on the Formation of Poly(amic acid) 4,4′-(Hexafluoroisopropylidene)diphthalic Anhydride (6FDA) and 4,4′-(Hexafluoroisopropylidene)bis(p-phenyleneoxy)dianiline (BAPHF). Reaction Activated by Microwave, Ultrasound and Conventional Heating

Abstract

Green chemistry is the design of chemical processes that reduce or eliminate negative environmental impacts. The use and production of chemicals involve the reduction of waste products, non-toxic components, and improved efficiency. Green chemistry applies innovative scientific solutions in the use of new reagents, catalysts and non-classical modes of activation such as ultrasounds or microwaves. Kinetic behavior and non-thermal effect of poly(amic acid) synthesized from (6FDA) dianhydride and (BAPHF) diamine in a low microwave absorbing p-dioxane solvent at low temperature of 30, 50, 70 °C were studied, under conventional heating (CH), microwave (MW) and ultrasound irradiation (US). Results show that the polycondensation rate decreases (MW > US > CH) and that the increased rates observed with US and MW are due to decreased activation energies of the Arrhenius equation. Rate constant for a chemical process activated by conventional heating declines proportionally as the induction time increases, however, this behavior is not observed under microwave and ultrasound activation. We can say that in addition to the thermal microwave effect, a non-thermal microwave effect is present in the system.

A demonstration of athermal effects of continuous microwave irradiation on the growth and antibiotic sensitivity ofPseudomonas aeruginosaPAO1

“…However, there a few claims that microwaves affect the activation energy for a chemical reaction in way not easily attributable to purely thermal effects as predicted by the Arrhenius equation. [12][13][14][15] Interestingly, there are claims that microwaves do affect the rate of enzyme catalysed conducted athermally in vitro [16][17][18][19] which could have consequences for viability. significantly when the cell culture enter stationary phase.…”

“…Indeed, even for chemical reactions it is very difficult to critically compare different experiments as they have been carried out under a wide range of conditions and are often reported in insufficient detail to allow reliable replication. However, there a few claims that microwaves affect the activation energy for a chemical reaction in way not easily attributable to purely thermal effects as predicted by the Arrhenius equation . Interestingly, there are claims that microwaves do affect the rate of enzyme catalysed conducted athermally in vitro which could have consequences for viability.…”

Microwave-assisted Fenton’s oxidation of amoxicillin

“…If MW induce an increase in molecular vibrations, it is expected that pre-exponential factor in the Arrhenius equation will be affected positively and an increase in the chemical reaction rate occurs [38,46]. Since MW irradiation induces rotation and migration of polar molecules, it is expected that the system entropy increases and therefore, it can be postulated a reduction in the activation energy, enhancing the degradation rates [51].…”

A concise review on microwave-assisted polycondensation reactions and curing of polycondensation polymers with focus on the effect of process conditions

“…A comparative study of polyamic acid formation from dianhydride and diamine in a weak microwave absorbing solvent (p-dioxane) under conventional heating, microwaves and ultrasound irradiation was presented by Tellez et al [35]. The reaction was carried out over a low temperature range (30-70°C) under atmospheric pressure.…”