Dynamic mechanical behavior in the ethylene terephthalate-ethylene oxide copolymer with long soft segment as a shape memory material

Abstract

Several ethylene terephthalate-ethylene oxide segmented copolymers with long soft segments, in which poly(ethylene oxide) (PEO) chains serve as soft segments while poly(ethylene terephthalate) (PET) chains serve as hard segments, were investigated by dynamic mechanical analysis (DMA). The PET-PEO copolymers show three distinguishable relaxation processes, α-, β- and γ-relaxation, within the examined concentration range of PET in the copolymers, and α-relaxation was associated with the glass transition of PEO segments in amorphous phase. Both longer PEO segments and higher PET content would tend to decrease the α-relaxation temperature ( T α ). The intensity of tan δ for α-relaxation reduced with the increase of soft segment length, and increased with PET content in the PET-PEO segmented copolymer. DMA measurements were carried out on the samples containing 2000, 4000, 6000 and 10,000 PEO segments, respectively. Relations between the intensity of tan δ for α-relaxation and the maximum shape recovery ( R f ) were also discussed. Experiments revealed that small energy dissipation and high physical crosslinking effects supplied by the PET component in the copolymer would be favorable for the material to show a good shape recovery.