AbstractReactivity ratios have been determined for the copolymerization of trimethyl aconitate with butadiene, styrene, acrylonitrile, and vinyl chloride, and for triethyl aconitate with butadiene and styrene. The values obtained indicate that trialkyl aconitates are very reactive in free radical initiated copolymerizations. No copolymerizations of aconitic acid were realized. A copolymer of butadiene and trimethyl aconitate has been prepared in a modified Mutual recipe at 50°C. The copolymer shows fair oil resistance and tensile properties but the low‐temperature properties are poor. The temperature rise of trimethyl aconitate copolymer is possibly better than that of standard GR‐S made at