Synthesis of natural rubber-based telechelic cis-1,4-polyisoprenes and their use to prepare block copolymers via RAFT polymerization

摘要

A new trithiocarbonate functionalized cis-1,4-polyisoprene was obtained from oxidative degradation of natural rubber followed by reductive amination and amidation. The structure of the resulting functionalized cis-1,4-polyisoprene was confirmed by a combination of ~1H NMR spectroscopy, ~(13)C NMR spectroscopy, MALDI-TOF mass spectrometry and FTIR spectroscopy. ~1H NMR spectroscopy showed that the trithiocarbonate functionality was equal to one. The well-defined trithiocarbonyl-end functionalized cis-1,4-polyisoprene was used as a macromolecular chain transfer agent (macroCTA) to mediate the RAFT polymerization of t-BA using AIBN as the initiator ([t-BA]_0/[macroCTA]_0/[AIBN]_0 = 250/1/0.2) in toluene at 60 °C. The resulting PI-b-P(t-BA) diblock copolymer presents an unimodal SEC trace shifted toward higher molecular weight in comparison with the SEC trace of the macroCTA, indicating that the polymerization of the second block is effective. The characteristics of the copolymer were determined by SEC (M?_n = 26,000 g mol ~(-1), PDI = 1.76) and ~1H NMR spectroscopy (DP?_n (PI) = 62 and DP?_n (P(t-BA)) = 87).