Tunable Adhesion from Stoichiometry-Controlled and Sequence-Defined Supramolecular Polymers Emerges Hierarchically from Cyanostar-Stabilized Anion–Anion Linkages

Abstract

Sequence-controlled supramolecular polymers offer new design paradigms for generating stimuli-responsive macromolecules with enhanced functionalities. The dynamic character of supramolecular links present challenges to sequence definition in extended supramolecular macromolecules, and design principles remain nascent. Here, we demonstrate the first example of using stoichiometry-control to specify the monomer sequence in a linear supramolecular polymer by synthesizing both a homopolymer and an alternating copolymer from the same glycol-substituted cyanostar macrocycle and phenylene-linked diphosphate monomers. A 2:1 stoichiometry between macrocycle and diphosphate produces a supramolecular homopolymer of general formula (A)n comprised of repeating units of cyanostar-stabilized phosphate–phosphate dimers. Using a 1:1 stoichiometry, an alternating (AB)n structure is produced with half the phosphate dimers now stabilized by the additional counter cations that emerge hierarchically after forming the stronger cyanostar-stabilized phosphate dimers. These new polymer materials and binding motifs are sufficient to bear normal and shear stress to promote significant and tunable adhesive properties. The homopolymer (A)n, consisting of cyanostar-stabilized anti-electrostatic linkages, shows adhesion strength comparable to commercial superglue formulations based on polycyanoacrylate but is thermally reversible. Unexpectedly, and despite including traditional ionic linkages, the alternating copolymer (AB)n shows weaker adhesion strength more similar to commercial white glue based on poly­(vinyl acetate). Thus, the adhesion properties can be tuned over a wide range by simply controlling the stoichiometric ratio of monomers. This study offers new insight into supramolecular polymers composed of custom-designed anion and receptor monomers and demonstrates the utility of emerging functional materials based on anion–anion linkages.

Supramolecular adhesive materials from small‐molecule self‐assembly

“…An overview of typical examples with adhesion strength over 1 MPa on diverse substrates is shown in Table 1. 23,53,[55][56][57][58][59][60][61][62] Typical molecular weights of these monomers are below 2,000 g/mol, with a minimum of 186 g/mol, whereas the binding strength values are comparable with those of commercial superglues, allowing SSSA to be worth investigated further as macroscopic adhesion materials.…”

Deep Eutectic Supramolecular Polymers: Bulk Supramolecular Materials

“…Because cyclodextrin‐acid‐based DESP s are solvent‐free and highly viscous, no permeation of the material was observed during adhesion testing with paper or textiles. In contrast to commercially available adhesives, the adhesion behaviors of cyclodextrin‐acid‐based DESP s are instantaneous and do not require tedious and time‐consuming solidification or pre‐processing …”

“…Lap‐shear adhesion tests were conducted to give a quantitative evaluation of adhesion strengths of cyclodextrin‐acid‐based DESP s . All cyclodextrin‐acid‐based DESP s exhibited high adhesion strengths on hydrophilic surfaces, including glass (up to 4.38 MPa) and iron (up to 6.57 MPa) (Figure ; see Figure S44).…”

“Texas-Sized” Molecular Boxes: From Chemistry to Applications

“…Renowned supramolecular hosts, such as crown ethers [ 7 , 8 ], cyclodextrins (CDs) [ 9 , 10 ], Stoddart’s “blue box” [ 11 ], calix[n]arenes [ 12 , 13 ], cucurbit[n]urils (CBs) [ 14 , 15 ], and pillar[n]arene [ 2 , 16 ] have been widely explored as building blocks for host–guest molecular recognition [ 17 , 18 ], energy storage [ 19 ], intelligent materials [ 20 , 21 , 22 , 23 ], drug delivery systems [ 24 , 25 , 26 , 27 ], and molecular machines [ 28 , 29 , 30 ], etc. A number of new synthetic macrocycles have been reported and have received considerable attention, such as Wang’s corona[n]arenes [ 31 ], Jiang’s oxatub[4]arene [ 32 ], Flood’s cyanostar [ 33 ], and others [ 34 ]. Among the cationic macrocycles, the tetracationic cyclobis(paraquat- p -phenylene) (CBPQT 4+ ), also known as the “blue box” [ 11 ] and structurally related macrocycles developed by Stoddart and co-workers, are probably the most iconic.…”