Probing the Interactions between Mimics of Pour Point Depressants (PPDs) and Viscosity Index Improvers (VIIs) in Engine Oil Using Fluorescently Labeled PPDs

Abstract

The level of interpolymeric interactions experienced by a pyrene-labeled poly­(octadecyl methacrylate) labeled with 6.7 mol % of 1-pyrenebutanol (Py(6.7)-PC18MA) was characterized by fluorescence in the presence of an amorphous (EP­(AM)) and a semicrystalline (EP­(SM)) ethylene propylene copolymer. These polymers belong to different families of engine oil additives. The fluorescence spectra of Py(6.7)-PC18MA solutions in engine oil were acquired and analyzed to obtain f inter, the molar fraction of pyrene labels that formed excimer intermolecularly upon encounter between an excited- and a ground-state pyrene. The fraction f inter was measured as a function of solution temperature between −30 and +25 °C. The f inter-vs-T profiles obtained for Py(6.7)-PC18MA showed a sharp transition between +10 and +15 °C, indicating an increase in intermolecular interactions at temperatures lower than the transition. This behavior was attributed to the crystallization of the PC18MA octadecyl side chains. Addition of EP­(AM) resulted in an increase in interpolymeric interactions between Py(6.7)-PC18MA macromolecules at all solution temperatures studied. Addition of EP­(SM) increased f inter for Py(6.7)-PC18MA at high temperatures, but at lower temperatures where EP­(SM) formed microcrystals, f inter for Py(6.7)-PC18MA returned to its original value when no EP­(SM) was present in solution. These trends indicated that PC18MA interacted with the EP copolymers as long as the copolymers remained solvated. Crystallization of EP­(SM) released the polyolefin from PC18MA, and PC18MA resumed its original level of intermolecular interactions as if no polyolefin was present in the solution. These experiments extended our earlier finding established with pyrene-labeled EP copolymers that f inter is a powerful analytical means to quantify the level of intermacromolecular interactions taking place during the crystallization of polymers and monitor their interactions with other macromolecules in solution.

End Group Analysis of Polyisobutylene Succinic Anhydride (PIBSA) Carried Out with Pyrene Excimer Fluorescence

“…The 1-pyrenemethylsuccinimide (PySI) group has been used effectively to probe the interactions in solution between pyrene-labeled polyolefins having different macromolecular architectures through pyrene excimer formation (PEF) resulting from the encounter between an excited and a ground state pyrene. ,− Consequently, a PIBSA sample, assumed to be a mixture of PIBSA 1 and PIBSA 2 species, was labeled with PyMA to yield a mixture of PIB-PySI 1 and PIB-PySI 2 species bearing one or two PySI groups, respectively. In turn, their time-resolved fluorescence decays could be analyzed with the MFA to determine f doubly , the molar fraction of PIBSA 2 species in a PIBSA sample.…”

Effect of Pour Point Depressants on the Impedance Spectroscopy of Waxy Crude Oil

“…Waxy crude oils treated by an effective PPD present pour point, viscosity, and yield stress lower than those of the untreated oils. Conventional commercial pour point depressants usually belong to one of the following three general chemical families: ethylene/vinyl acetate (EVA) copolymer, polyacrylate copolymer, and maleic anhydride copolymer. − Research efforts to discover novel and more “potent” wax controlling chemicals beyond the aforementioned commercial types have also been undertaken. It has been shown recently that nanometer/micron-sized particles grafted with traditional pour point depressant molecules can outperform neat traditional pour point depressants. − It is accepted that pour point depressants generally disrupt the intrinsic crystallization characteristics of wax molecules, leading to “looser-than-original” microstructure of the wax-in-oil suspension , and improved flowability of the waxy crude oil at low temperatures.…”