Supramolecular polymer materials based on ureidopyrimidinone quadruple hydrogen bonding units

Supramolecular polymer materials are polymeric structures that are physically crosslinked by non-covalent interactions such as ionic interactions, host-guest complexation and hydrogen bonding. The resulting materials generally display stimuli-responsive behavior and/or healable properties, which makes them excellent candidates for the design of dynamic materials. Inspired by its omnipresence in natural systems, hydrogen bonding has proven to be useful for the development of synthetic materials with dynamic properties. Inspired by the base-pairing in the DNA double helix, Meijer et al. developed the self-complementary quadruple hydrogen bonding unit ureidopyimidinone (UPy), which has a strong dimerization constant (K_dim > 10⁷ M ⁻¹ ). The incorporation of UPy motifs in polymeric precursors led to a plethora of hydrogen bonded materials with applications ranging from artificial arteries to reversible adhesives. This review will focus on design strategies to synthesize these UPy-containing polymer materials, which can be split into three main categories based on the location of the UPy arrays: UPy in the main-chain, UPy in the side-chains or UPy at the chain-ends. In addition to the synthetic routes, the material properties of the resulting UPy-containing supramolecular polymer materials will be discussed.