Improved elastic recovery from ABC triblock terpolymers

The promise of ABC triblock terpolymers for improving the mechanical properties of thermoplastic elastomers is demonstrated by comparison with symmetric ABA/CBC analogs having similar molecular weights and volume fraction of B and A/C domains. It is shown that the ABC architecture enhances elasticity (up to 98% recovery over 10 cycles) in part through essentially full chain bridging between discrete hard domains leading to minimization of mechanically unproductive loops. In addition, the unique phase space of ABC triblocks also enables the fraction of hard-block domains to be higher (fhard ≈ 0.4) while maintaining elasticity, which is traditionally only possible with non-linear architectures or highly asymmetric ABA triblock copolymers. These advantages of ABC triblock terpolymers provide a tunable platform to create materials with practical applications while improving our fundamental understanding of chain conformation and structure–property relationships in block copolymers., 1H nuclear magnetic resonance spectroscopy
Solution state 1H nuclear magnetic resonance (NMR) spectra were recorded on a Varian VNMRS 600 MHz spectrometer. Chemical shifts (δ) are reported in ppm relative to residual protio-solvent in CDCl3 (7.26 ppm).
Size-exclusion chromatography instrumentation
Size-exclusion chromatography (SEC) was performed on a Waters instrument using a differential refractive index detector and two Tosoh columns (TSKgel SuperHZM-N, 3 μm polymer, 150 × 4.6 mm) with chloroform containing 0.25% TEA at 35 °C as the mobile phase. Molar masses and molar mass dispersity (Đ) were determined against narrow PS standards (Agilent). 
Mechanical analysis
Frequency sweeps and isochronal temperature sweeps were obtained on a TA Instruments ARES G2 in oscillatory shear mode with a 25 mm parallel-plate geometry and a nitrogen-purged forced–convection oven. For all experiments, oscillatory shear was applied within the linear viscoelastic regime as verified from isochronal strain ...,