Thermo-reversible solid-like and liquid-like behaviors of carboxyl-terminated telechelic poly(ethylene-butylene) neutralized by octadecylamine

Solid-like and liquid-like viscoelastic behaviors at low and high temperature, T, respectively, observed for carboxylterminated telechelic poly(ethyrene-butylene) (CTPEB) neutralized with octadecylamine ODA prepared by melt mixing are studied in relation with the structure examined by XRD, FT-IR, DSC and small angle neutron scattering. When the mole ratio of -NH₂ and -COOH, NH₂/COOH in CTPEB/ODA is 1.4 or higher, CTPEB/ODA was solid-like at 298K, while it was liquid-like having almost the same viscosity as CTPEB at 343K. The network structure formed at low T was easily fractured by small strain and cannot be reformed at low T. However, when the sample is annealed at 353K, cooled and kept for a few hours at T < 300K, the solid-like behavior is reproduced. It was concluded that the network formation at low T and its disappearance at high T for CTPEB/ODA is caused by non-crystalline association/ dissociation of C18 residues in ODA connected to CTPEB by ionic bond (NH₃⁺COO^-). Due to the small M_w of CTPEB, only longer chains (~ 1/3 of total chains) connected to ODA aggregates form network structure and sustain the constant G' in this system at low T.