Synthesis of Liquid Polyisoprene via Anionic Chain Transfer Polymerization and Its 100‐Fold Scale‐Up in a 2‐Liter Reactor

The primary synthesis of liquid rubber via anionic polymerization requires substantial alkali metal initiators, resulting in high costs. This study introduces a metal‐free chain transfer agent (CTA), 9,10‐dihydroanthracene (DHA), into the anionic polymerization of isoprene (Ip). A series of liquid polyisoprenes (PIp) with number‐average molecular weights ( M n ) ranging from 2100 to 6800 g/mol were synthesized. Furthermore, the correlation between DHA, THF dosage, and reaction temperature and the resulting polymer structures was established. The results indicate that at 20°C, DHA induces chain transfer during the anionic polymerization of Ip. Moreover, higher dosages of both DHA and THF led to lower M n and polydispersity index (PDI) of the resulting PIp, corresponding to a lower degree of polymerization (). Concurrently, the initiator efficiency ( E I ) and chain transfer constant ( C M ) increased. Conversely, −25°C effectively suppressed chain transfer, while 60°C did not significantly promote the process. To validate its practical potential, a 100‐fold scale‐up experiment was performed. This yielded a series of liquid PIp with M n below 2500 g/mol, PDI below 1.21, E I greater than 20.0, and C M greater than 2.8 × 10 − 2 . It provides crucial theoretical and experimental foundations for advancing the preparation technology of liquid rubber.