The generated thiyl radicals then perform rapid addition of another thiocyanate substituted olefins as well documented. Bulky radicals stabilized by a (hetero)aryl or ester groups can also undergo this cyano group migration pathway, enabling the radical homopolymerization of α-substituted styrenic and acrylate monomers. This strategy can achieve a library of ABC sequence-regulated polyacrylonitrile copolymers with different functionalities (Figure ). The thiocyanate monomers are easily accessed by the substitution of homo-allylic bromide or triflate up to 10 g scale. The radical polymerization of 4-thiocyanato-1-butene was initially examined using azobis(isobutyronitrile) (AIBN) as an initiator in 1,4-dioxane (2 M) at 80 °C. The full conversion was achieved after 12 hours. A light-yellow viscous liquid was yielded. The polymer has good solubility in polar solvents like N, N-dimethylformamide, and dimethylsulfoxide, but it does not dissolve in dichloromethane, tetrahydrofuran, or 1,4-dioxane. The yielded polymer was analyzed by size exclusion chromatography (SEC), giving the number-averaged molecule weight (Mn) of 28.7 k and dispersity (Đ) of 2.39 (Table , entry 1). The polymerization in different solvents was subsequently studied. Dioxane and THF were found to give high conversion (Table , entries 2-5), even at a more dilute condition (Table , entry 6). Using peroxide initiators such as benzoyl peroxide (BPO) and di-tert-butyl peroxide (DTBP) cannot give any polymers. That can be probably attributed to the generated oxygen radicals that would abstract the hydrogen atoms at the allylic position, failing the initiation step. The success of this functional group migration polymerization requires high efficiency for each step. To gain more insight, we synthesized and tested other monomers. As shown in Table , if we add one more carbon spacer between the olefin and thiocyanate, no polymerization occurred. This observation suggested the formation of the five-member ring intermediate by radical cyclization is essential. Heteroaryls as migration groups connected to sulfur atoms or homo-allylic selenocyanate failed to deliver any polymers. Having identified the optimal polymerization conditions, we next explored the generality of this cyano group migration polymerization in order to access the library of alternating ABC sequence-regulated polymers. Alkyl or cycloalkyl can be introduced at the olefinic position or on the carbon next to thiocyanate, giving polymers P1-P6 with a sequence equal to poly (acrylonitrile-olefin-sulfur atom). The random copolymers of acrylonitrile with other styrenic or acrylate monomers are a worldwide commodity.