Facile synthesis of tertiary amine functionalized liquid polyisoprene rubber by LAP with 1,2-Dipiperidinoethane derivatives as modifier

The properties of polydiene-based liquid rubber are controlled by the microstructure, sequence distribution and degree of functionalization. The living anionic polymerization (LAP) initiation (alkyl-metal nucleophiles) and regulation (electron-rich Lewis bases) systems and polymerization conditions (such as temperature, solvent and charging mode) as well as the functionality comonomer need to be optimized to achieve excellent control of polymer structure. Herein, with the assistance of the 1,2-dipiperidinoethane (DPE) derivatives with different steric hindrance and electron effect substituents, the high vinyl polyisoprene (HVPI, 80 % < 3,4- & 1,2-units < 92 %, 1,2-units up to 26 %) liquid rubber was obtained with n-BuLi as initiator in cyclohexane. Furthermore, the synthesis of HVPI with quantitatively tertiary-amine functionalization, ranging from 0 % to 25 % molar ratio, was achieved through in-situ living anionic polymerization (LAP) using 4-dimethylaminomethylstyrene (VBN) as a polar comonomer. Precise control of molecular weight and tertiary amine functionalization can be achieved above room temperature. The fine structure of the product was analyzed using FTIR, GPC, ¹H NMR, ¹³C NMR, and DSC techniques. The polymerization mechanism was also proposed to explain the formation of highly selective vinyl side groups.