Synthesis and characterization of poly(tetramethylene oxide)-based segmented ionenes block copolymer with aliphatic or DABCO hard segments

Abstract

In this study, the effects of the contents of the soft and hard segments as well as the type of hard segments (linear aliphatic and DABCO) on the properties of PTMO-based segmented ionenes were investigated. DSC revealed that soft segment weight fractions up to 75 wt% induced heterogeneous crystallization while the melting temperature decreased due to the lower degree of crystallization. DMA showed the formation of a higher degree of ionic aggregates in both linear aliphatic and DABCO-based PTMO ionenes with 25 wt% of soft segment resulting from strong Coulombic interactions between hard segments. DABCO-based ionenes showed a higher degree of phase separation compared to linear aliphatic analogs and displayed a long-range ordered lamellar structure. In contrast, linear aliphatic ionenes showed the formation of random ionic domains, which was confirmed by SAXS and AFM. TGA showed that the PTMO-based ionenes were thermally stable up to 250 °C and suggested that the DABCO hard segment has a weaker protective effect against the degradation of the PTMO soft segment at elevated temperatures compared to the linear aliphatic hard segment. Uniaxial tensile tests exhibited stress-induced crystallization of PTMO-based ionenes, high elongation at break with linear aliphatic hard segment compared to the DABCO hard segment, and the opposite trend of Young's modulus and ultimate tensile strength by changing the type of the hard segment.