Relaxation time, activation energy, and reaction pathway determination of the poly(ethylene glycol dimethacrylate)–dopant (I₂) interaction with the nuclear magnetic resonance technique

Abstract

Conductive polymers were obtained with a new polymerization method in which UV light was used as a photochemical initiator. In a previous work, optimum irradiation times were determined to obtain high conversion percentages. The effect of dopants on the conductivity of the polymer poly(ethylene glycol dimethacrylate) (PEGDM) was studied with LiClO 4 and I 2 as a dopant. The most effective dopant concentration was determined by the measurement of conductivities. Through the tracing of the conductivity change at various temperatures during the reaction of PEGDM with the dopant, the activation energies of the interactions were calculated, and a method was developed to follow the kinetics of the polymerization reaction with a conductometric technique. This work presents a nuclear magnetic resonance (NMR) study of the same polymer prepared under the optimum conditions with the results obtained in a previous study. NMR spectroscopy was used to determine the relaxation time, rate constants, and activation energy of the polymer-dopant interactions. As a preliminary study, pyruvic acid was used, and for acid-catalyzed pyruvic acid/water reactions, the relaxation time, activation energy, and enthalpy change values (⌬H) were determined. With the same NMR technique, the reaction mechanisms of the polymerization, relaxation times, and rate constants of the polymer-dopant interactions were determined. The polymerization pathway was determined with NMR spectra; the results were confirmed by the calculation of the activation energies and bond-breaking energies.

Synthesis of Ethylene Glycol Dimethacrylate-Methyl Methacrylate Copolymers, Determination of their Reactivity Ratios, and a Study of Dopant and Temperature Effects on their Conductivities

“…At a certain temperature the conductivity showed a sudden increase [17]. The aim of the present study was to determine if the PMMA homopolymer and its copolymer with EDGMA gave the same characteristic behavior as was obtained for EGDMA homopolymer, in other words, to determine when EGDMA is copolymerized with MMA to increase its mechanical strength, if it will still show the same trend of conductivity change with temperature, and if it is still suitable for use in industry.…”

“…The conductivity of PEGDMA with dopant (LiClO 4 ) shows values in the millisiemens range (Table 6, Figure 12) (e.g., 9.0 mS at 26 °C) [17]. The conductivity of PMMA with the same dopant shows much smaller values than PEGDMA, in microsiemens range (Figure 14) (e.g., 24 µS at 25 °C).…”

“…The results are presented in Table 6. At first a decrease in conductivity with increasing temperature (up to 18.2 °C) is seen; then it shows a sudden increase [17]. Figures 13 and 14 show the conductivity values of PMMA without and with dopant (LiClO 4 ) at different temperatures.…”

“…The tubes were sealed with a septum and connected to the high vacuum system with a syringe needle and degassed to 10 torr for 5-6 hours. The degassed tubes were then irradiated with the UV source [17]. After 30 minutes of irradiation the obtained polymer was dissolved in THF which is a good solvent for both the monomer and polymer, then precipitated in methanol.…”

“…The resulting polymer was filtered and dried in a vacuum oven at room temperature to a constant weight. When dopant addition is required, about 0.3-0.4 M dopant was incorporated with the monomer solution system before polymerization or it was added to the polymer solution after polymerization [17].…”