AbstractCationic copolymerizations of furfural were carried out with several vinyl monomers. No copolymers were obtained with some hydrocarbon comonomers. At low temperatures furfural copolymerized with vinyl ethers selectively through the aldehyde group. On the other hand, deeply‐colored copolymers of complex structures were formed at higher temperatures (ca.0°C). Three typical vinyl ethers (p‐tolyl vinyl ether, dihydropyran, and divinyl ether) were selected as comonomers, and their copolymerization behaviour studied in detail. The monomer reactivity ratios for furfural (M1) andp‐tolyl vinyl ether (M2) werer1= 0,15 ± 0,15,r2= 0,25 ± 0,05. The furfural (FF) contents were fairly independent of the monomer feeds when dihydropyran (DHP) and divinyl ether (DVE) were used as comonomers: 37–47% for FF‐DHP copolymers and 40–50% for FF‐DVE copolymers. More than half of the second vinyl groups were consumed in the FF‐DVE copolymers indicating the formation of 1,3‐dioxane rings as in the case of benzald