Supramolecular Polymers from Linear Telechelic Siloxanes with Quadruple-Hydrogen-Bonded Units

Abstract

Telechelic oligo- and poly(dimethylsiloxanes) 1 and 2, with two ureidopyrimidone (UPy) functional groups, have been prepared via a hydrosilylation reaction. The compounds have been characterized in solution by 1H NMR and viscometry and in the solid state by 1H NMR and 13C NMR, FTIR, and rheology measurements. The measurements show that the UPy groups of 1 and 2 are associated via quadruple hydrogen bonds in a donor−donor−acceptor−acceptor (DDAA) array. In many aspects, the materials behave like entangled, high molecular weight polymers. Compound 2 has a Tg at −119 °C and shows melting of microcrystalline domains of associated UPy units at −25 °C. Compound 1 has a crystalline form (Tm = 112 °C) and an amorphous modification with a Tg of 25 °C. Solid-state NMR was used to investigate the mobility of these phases. WISE spectra show a higher mobility of the UPy groups in the amorphous phase than in the crystals of 1. Amorphous 1 and 2 behave like entangled polymers. Their mechanical behavior is characterized ...