Synthesis and block-specific complexation of poly(ethylene oxide)-poly(tetrahydrofuran)-poly(ethylene oxide) triblock copolymers

Well‐defined ABA triblock copolymers in which A stands for poly(ethylene oxide) (PEO) and B for poly(tetrahydrofuran) (PTHF) were synthesized by end‐capping bifunctionally living PTHF with different polyethylene glycol–monomethylethers. Differential scanning calorimetry analysis of these copolymers showed two melting points: one around 55 °C due to the PEO blocks, and one around 30 °C due to the PTHF segments, demonstrating that these block copolymers show extensive phase separation. Upon addition of sodium thiocyanate, crystalline complexes with PEO were formed and as a consequence, the melting points of the PEO segments had shifted to approximately 170 °C, whereas the melting points of the PTHF segments decreased slightly. The obtained materials behave as thermoplastic elastomers up to 160–175 °C. The influence of the relative lengths of the PEO and the PTHF segments on the thermal and mechanical properties of the materials have been investigated. Copyright © 1999 John Wiley & Sons, Ltd.