Synthesis of amine-capped Trans-1, 4- polyisoprene

Abstract

Polymer chain-end functionalization with polar groups can significantly improve the hydrophilicity of the polymers. In this work, a facile strategy was proposed for synthesis of amine-functionalized trans-1,4-polyisoprenes (F-TPI) with heterogeneous TiCl4/MgCl2 type Ziegler-Natta catalyst by using dicyclohexylamine (DCHA) as chain-transfer agents (CTA). The microstructure and molecular weight of F-TPI were analyzed by 1H NMR and GPC. With the increase in DCHA/isoprene (IP), the amine-capped efficiency (CE) of the obtained F-TPI increased and the number-average molecular weight (Mn) decreased accordingly, accompanied with the reduced polymerization activity. The F-TPI sample was separated into low-molecular-weight (LMW) fractions with about 98% CE and high-molecular-weight (HMW) fractions with about 30% CE by using precipitation fractionation method. The isoprene polymerization kinetics in the presence of DCHA revealed that the CE in the polymers reached 98.5% in the initial polymerization stage (about 1.8 wt% conversion) and then decreased gradually with the polymerization time extention. The chain end structures and possible chain transfer reactions were proposed to explain the fraction formation in F-TPI. The water contact angle of the obtained F-TPI decreased with increased CE, indicating higher hydrophilicity of the F-TPI membranes.