Catalytic Etherification of ortho-Phosphoric Acid for the Synthesis of Polyurethane Ionomer Films

Abstract

The etherification reaction of ortho-phosphoric acid (OPA) with polyoxypropylene glycol in the presence of tertiary amines was studied. The reaction conditions promoting the catalytic activity of triethanolamine (TEOA) and triethylamine (TEA) in the low-temperature etherification of OPA were established. The catalytic activity of TEOA and TEA in the etherification reaction of phosphoric acid is explained by the hydrophobic-hydrophilic interactions of TEA with PPG, leading, as a result of collective interactions, to a specific orientation of polyoxypropylene chains around the tertiary amine. When using triethylamine, complete etherification of OPA occurs, accompanied by the formation of branched OPA ethers terminated by hydroxyl groups and even the formation of polyphosphate structures. When triethanolamine is used as a catalyst, incomplete etherification of OPA with polyoxypropylene glycol occurs and as a result, part of the phosphate anions remain unreacted in the composition of the resulting aminoethers of ortho-phosphoric acid (AEPA). In this case, the hydroxyl groups of triethanolamine are completely involved in the OPA etherification reaction, but the catalytic activity of the tertiary amine weakens due to a decrease in its availability in the branched structure of AEPA. The kinetics of the etherification reaction of OPA by polyoxypropylene glycol catalyzed by TEOA and TEA were studied. It was shown that triethanolamine occupies a central position in the AEPA structure. The physico-mechanical and thermomechanical properties of polyurethane ionomer films obtained on the basis of AEPA synthesized in a wide temperature range were studied.

Self-Organization of Polyurethane Ionomers Based on Organophosphorus-Branched Polyols

“…After TEOA is fully involved in the etherification reaction, excess OPA does not react with the terminal hydroxyl groups of AEPA-PEG or the remaining amount of PEG. In our previous studies [58], it was experimentally shown that the rate constant of the OPA etherification reaction with triethanolamine exceeds the rate constant of the OPA etherification reaction with polyoxypropylene glycol.…”

“…In [58], the role of associative interactions of tertiary amines and PPG in the catalytically activated low-temperature etherification of OPA was discovered and proven. According to our research [59], the use of PEG instead of PPG also makes it possible to synthesize the corresponding aminoethers of ortho-phosphoric acid (AEPA-PEG).…”

“…In [56][57][58][59], polyurethane ionomers were obtained using aminoethers of ortho-phosphoric acid (AEPA) as a polyol component. It was found that AEPA-PPG, synthesized using triethanolamine (TEOA), ortho-phosphoric acid (OPA), and polyoxypropylene glycol (PPG) with MM = 1000, is a branched structure that contains phosphate ions (Figure 1).…”