We report the design of bioinspired, reversible supramolecular thermoplastic elastomers (TPEs) functionalized with ureido-cytosine (UCyt) complementary quadruple hydrogen bonding (QHB) sites. The polymer contained a soft poly(n-butyl acrylate) central block that imparted flexibility and two external, hard nucleobase-containing blocks that contributed to structural integrity. In addition, the hard block with pendant QHB motifs served as efficient physical crosslinks to further enhance the thermomechanical performance, where the polymer service window extended up to 30 degrees C higher compared to the controls that bear dimeric hydrogen bonding units. The resulting UCyt copolymers also exhibited improved surface and bulk morphology, which self-assembled into well-ordered lamellar microstructures. Moreover, the polymer displayed an unexpected moisture-resistant property with less than 1 wt % equilibrium moisture uptake even at 95% relatively humidity, which presumably correlated with its well-ordered and densely-packed morphology facilitated by strong hydrogen bonding. Variable temperature Fourier-transform infrared spectroscopy experiments further confirmed the thermoreversibility of hydrogen bonding, indicating melt-processablility and recyclability of the polymer. These physical properties verified quadruple bonding dominated behavior, and structure-property-morphology relationships suggest key design parameters for future TPEs. (c) 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 13-23