Thermo- and water-induced shape memory poly(vinyl alcohol) supramolecular networks crosslinked by self-complementary quadruple hydrogen bonding
Poly(vinyl alcohol) (PVA) supramolecular networks cross-linked by ureido-pyrimidinone (UPy) dimers via strong quadruple hydrogen bonding in donor–donor–acceptor–acceptor (DDAA) arrays have been synthesized for the first time. This material displays excellent thermo- and water-induced shape memory behavior with a recovery ratio of nearly 99%. These UPys are dimerized as DDAA arrays, which present good stability in both water and alkaline solutions (pH 12), or at temperatures below 120 °C. UPy dimers act as a fixed phase to hold the material's permanent shape, whereas the PVA chains act as a reversible phase to control the temporary shape. This physical cross-linking, formed by UPy dimerization, can potentially replace traditional chemical cross-linking with covalent bonds, thereby providing a more simple and practical strategy to obtain multi-responsive shape memory polymers.