Hyperbranched-polyethyleneiminated functional polymers. III. Synthesizing thiophosphate-containing pseudodendritic poly-ethyleneiminated polyoxypropylenediamine and its behavior at an oil/metal interface under extreme pressure

A simple synthetic route for preparing a thiophosphate-containing pseudodendritic polyethyleneiminated polyoxypropylenediamine, D400(EI) _xP, is presented. The number of ethyleneimine group (EI) in D400(EI)_xP was determined by ¹H-and ¹³C-NMR to be 4.3 for D400(EI)₄P and 8.9 for D400(EI)₈P, and the extent of branch was quantitatively determined using potentiometric titration. The numbers of thiophosphate groups per thiophosphate-containing pseudodendritic polymers molecule for D400(EI)₀P, D400(EI)₄P, and D400(EI)₈P were calculated by elemental analyses of sulfur content. The AW performance of these synthesized thiophosphate-containing pseudodendritic polymers was examined by measuring the temperature of oil, and the frictional coefficient and electrical contact resistance between the two metal surfaces. More thiophoBphate groups on either side of D400(EI)₈P are found to increase the electrical contact resistance due to the chemical adsorption of thiophosphate groups onto metal surfaces, forming a thick layer and reducing operating time required to form the adsorption layer. Interestingly, the adsorption layers markedly reduce the frictional coefficient (∼ 0.012) and limit the increase in oil temperature (∼ 90°C) throughout the entire period of AW test, reducing weight loss of the metal (0.1 mg).