Glycoluril Clips for the Construction of Chemoresponsive Supramolecular Polymer Networks through Homodimer Cross-Links.

The formation of polymer supramolecular networks exhibiting selective sensitivity toward a narrow class of organic compounds is still a significant challenge within the area of reversibly cross-linked materials. Glycoluril molecular clips are U-shaped molecules, which, besides the ability to undergo self-sorting homodimerization, exhibit selectively high molecular recognition of dihydroxyaromatic species. A glycoluril clip diol was introduced into a polymer backbone by using standard polyurethane chemistry. Immobilization of the molecular clip along the polyurethane macromolecule (Glyc Clip-polyurethane) was shown to preserve the native association properties of the clip. Clip motifs embedded in macromolecules form homodimer cross-links in CHCl3 and the resulting structures have a thermoresponsive character. The strength of homodimerization Khomodimer varies from 7.74 104  l mol-1 at 265 K to 9.47 102  l mol-1 at 315 K. A 30 wt % solution of Glyc Clip-polyurethane undergoes gelation at room temperature and exhibits a constant elastic modulus, approximately 3.1 ⋅ 104  Pa, in the broad investigated frequency range. The obtained organogels exhibit selective chemoresponsive properties in the presence of resorcinol, which was demonstrated with 1 H high-resolution magic-angle-spinning NMR spectroscopy and rheological measurements.