Probing the Synergistic Effect of Modified Polyoctadecyl Acrylate and Asphaltenes on the Flowability of Waxy Oil

ABSTRACT The poor low‐temperature flowability of waxy crude oil, stemming from the formation of a continuous wax crystal network, poses a major operational and economic challenge to pipeline transportation. While polymeric pour point depressants (PPDs) and intrinsic asphaltenes are known to exhibit a synergistic flow‐enhancing effect, the mechanistic role of PPD molecular architecture—specifically the impact of polar and aromatic functional groups—remains inadequately defined. To address this, a series of structurally tailored comb‐like PPDs were synthesized via radical copolymerization of octadecyl acrylate with vinyl acetate (POV), maleic anhydride (POM), or styrene (POS). Their synergistic interactions with asphaltenes (0.75 wt%) in a model waxy oil were systematically deciphered through pour point measurements, rheological analysis, differential scanning calorimetry (DSC), polarized light microscopy, and molecular dynamics (MD) simulations. Results indicate that for oil without asphaltenes, polyoctadecyl acrylate (POA) performed best, lowering the pour point by 9°C. Remarkably, in the presence of asphaltenes, PPDs incorporating polar or aromatic comonomers outperformed POA significantly, with POS‐3 achieving a 24°C pour point reduction. Microscopy and MD simulations revealed that polar/aromatic groups enhance PPD‐asphaltene interaction, leading to the formation of composite particles that template the growth of larger, more spherical wax crystals, thereby effectively disrupting the three‐dimensional network. This work establishes a clear structure‐activity relationship and provides a molecular‐level design principle for developing high‐efficiency composite PPDs, contributing to the fundamental understanding and practical application of flow assurance strategies.