Synthesis of comb‐like dispersants and a study on the effect of dispersant architecture and carbon black dispersion

ABSTRACT Comb dispersants suitable for stabilization of carbonaceous deposits found in automotive lubricating oils were derived from the copolymerization of vinyl‐ether terminated polyisobutylene (VE‐PIB) macromonomers with maleic anhydride (MAH). The rate and degree of copolymerization of VE‐PIB with MAH was greatly influenced by the molecular weight of the VE‐PIB. Longer PIB tails imposed greater hindrance of the chain end resulting in slower propagation and lower degrees of copolymerization for PIB‐ alt ‐MAH copolymers. Functionalization of PIB‐ alt ‐MAH with a polyamine proceeded smoothly at elevated temperatures as evidenced by disappearance of anhydride stretches via Fourier transform infrared spectroscopy. Analogous linear and grafted dispersants were prepared to investigate the influence of architecture on the physical properties of the dispersants. Characterization of the intermediates and final dispersants was conducted by nuclear magnetic resonance, gel permeation chromatography, thermogravimetric analysis, and ultraviolet–visible. Using Langmuir adsorption studies and carbon black as a substitute for carbonaceous deposits, it was found that comb and grafted dispersants exhibit greater affinities for adsorption but decreased packing efficiencies in comparison to linear dispersants. Rheological studies investigating viscosity as a function of loading for dispersant/oil mixtures with carbon black present a similar finding. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1682–1696