Low-molecular-weight supramolecular adhesives based on non-covalent self-assembly of a small molecular gelator.

Currently developed adhesives are overwhelmingly polymeric in nature. Herein, we highlight for the first time the potential of supramolecular eutectogels assembled from small molecules as robust low-molecular-weight (LMW) supramolecular adhesives in air, water and organic solvents, and under low temperatures. These supramolecular eutectogels were produced from commercial alkyl trimethyl ammonium bromide (CnTAB) in emerging deep eutectic solvents (DESs), which demonstrated rapid (∼2 min), robust, and tunable adhesion to both hydrophilic and hydrophobic surfaces at room temperature in air. Moreover, high adhesion performance was maintained even in liquid nitrogen (-196 °C), underwater, and in organic solvents. A study of the structure-property relationship of these adhesives and molecular dynamics (MD) simulations further clarified the assembly and adhesion mechanism of the C12TAB molecules in DESs. Compared with traditional polymer adhesives and several existing examples of LMW supramolecular adhesives with solvent-free dry network structures, the spontaneous self-assembly of LMW gelators in versatile DESs provides a new strategy for the facile construction of high-strength supramolecular adhesives with gel network structures for a diverse range of harsh environments.

Aluminum complexes with bidentate amido ligands: synthesis, structure and performance on ligand-initiated ring-opening polymerization of rac-lactide.

A series of mononuclear aluminum dimethyl complexes bearing bidentate N-[2-(1-piperidinyl)benzyl]anilino or N-(2-morpholinobenzyl)anilino ligands were synthesized via reactions of the corresponding proligands with trimethylaluminum upon heating, while at ambient temperature two trimethylaluminum adducts with neutral N-[2-(1-piperidinyl)benzyl]aniline proligands were obtained. These complexes were well characterized by NMR spectroscopy, elemental analysis and occasionally by EI-HRMS. The molecular structures of the typical trimethylaluminum adduct 2b and aluminum dimethyl complex 3b were further confirmed by X-ray diffraction studies. All the aluminum dimethyl complexes could effectively initiate the ring-opening polymerization (ROP) of rac-lactide in a well-controlled manner to afford PLAs with narrow molecular weight distributions (PDI = 1.06-1.18). The polymer samples obtained are systematically end-capped with the bidentate ancillary ligands as characterized by (1)H NMR and ESI-TOF mass spectroscopy. Moreover, the introduction of substituent(s) at the ortho-position(s) of the anilino moiety in the ligand results in an obvious decrease in the catalytic activity of the corresponding aluminum complex, and complexes with meta-chloro substituted anilino units show higher activities likely due to the enhanced electrophilicity of the metal centers induced by the anilino groups.