Monomer Sequence Architecture Tunes the Performance of Poly(octadecyl acrylate- co -styrene) Pour Point Depressants in Waxy Oils

Abstract Monomer sequence architecture is an underexplored design parameter for polymeric pour point depressants (PPDs). Here, octadecyl acrylate-styrene (OA-St) copolymers with statistical, block, and gradient architectures were synthesized by free-radical and reversible addition–fragmentation chain-transfer (RAFT) polymerization. Time-resolved 1H NMR spectroscopy and GPC supported the progressive compositional and molar-mass evolution expected for the intended gradient architecture for P(OA-g-St) 3:1. The prepared copolymer series exhibited distinct low-temperature behavior of both model wax oil and Daqing crude oil. The gradient copolymer with an OA/St ratio of 3:1 showed the best overall performance, reducing the model-oil pour point from 26.0 to 7.0 °C and the viscosity at 10 °C by approximately 97%. It also decreased the pour point of Daqing crude oil from 32.0 to 25.0 °C. DSC and quantitative microscopy showed that the gradient architecture weakened wax crystallization and produced compact, uniformly dispersed wax crystals. These observations are consistent with, but do not directly establish, a working model in which the programmed OA/St distribution regulates wax association, crystal growth, and wax-network organization. Within the investigated OA/St system, the results identify programmed monomer distribution as a promising design variable for PPD performance.