Synthesis of comb‐type copolymers with various pendants and their effect on the complex rheological behaviors of waxy oils

To improve the flowability of waxy crude oil containing a high concentration of asphaltenes (AS), novel comb‐type copolymers of poly(maleic acid polyethylene glycol ester‐co‐α‐octadecene) (PMAC) and poly(maleic acid aniline amide‐co‐α‐octadecene) (AMAC) with various grafting ratios (R_g) of PEG/aniline to maleic anhydride are synthesized. Model oils containing wax mixtures and AS are prepared to explore the effect of asphaltene concentration and the copolymers on the yield stress. The influence of the copolymers on the wax appearance temperature (WAT) of Liaohe high waxy oil is examined by rheological and microscopic methods. Experimental flow curves of shear stress as a function of shear rate are fitted following the Casson model to interpret the rheological properties of gelled waxy crude oil in the presence of AMACs, PMACs, and MAC. Compared with MAC, PMACs, and AMACs are more efficient in reducing the yield stress of both model oil and crude oil, which indicates a better flowability. It is found that PMAC1.0 and AMAC1.0 with a medium R_g can balance the interaction of copolymers with waxes and AS and reduce the yield stress much more than others. Between them, AMAC1.0 that possesses aromatic pendants is better than PMAC1.0, which only has polar pendants. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41660.