A Competing Hydrogen Bonding Pattern to Yield a Thermo‐Thickening Supramolecular Polymer

Abstract

Introduction of competing interactions in the design of a supramolecular polymer (SP) creates pathway complexity. Ester–bis‐ureas contain both a strong bis‐urea sticker that is responsible for the build‐up of long rod‐like objects by hydrogen bonding and ester groups that can interfere with this main pattern in a subtle way. Spectroscopic (FTIR and CD), calorimetric (DSC), and scattering (SANS) techniques show that such ester–bis‐ureas self‐assemble into three competing rod‐like SPs. The previously unreported low‐temperature SP is stabilized by hydrogen bonds between the interfering ester groups and the urea moieties. It also features a weak macroscopic alignment of the rods. The other structures form isotropic dispersions of rods stabilized by the more classical urea‐urea hydrogen bonding pattern. The transition from the low‐temperature structure to the next occurs reversibly by heating and is accompanied by an increase in viscosity, a rare feature for solutions in hydrocarbons.

Influence of the Z/E Isomerism on the Pathway Complexity of a Squaramide‐Based Macrocycle

“…One of the strategies to generate kinetically trapped supramolecular polymorphs consists of using molecules displaying two (or more) markedly distinct interaction patterns competing for the formation of two (or more) distinct assemblies. [ 38–50 ] For instance, Würthner and coworkers reported on an amide‐functionalized perylene bisimide dye able to self‐assemble into three supramolecular polymorphs via three different hydrogen bonding (H‐bonding) motifs inducing different π−π interaction profiles. [ 39 ] This kind of interaction versatility has also been observed in N ‐heterotriangulene dyes [ 49 ] and Pt complexes, [ 50 ] that rely on symmetry aspects and cis/trans coordination isomerism, respectively, to constitute different assembled isoforms.…”

Chain-End Effects on Supramolecular Poly(ethylene glycol) Polymers

“…In recent years, the highly directional physical interactions based on H-bonds have been applied in a fundamentally different way to form supramolecular polymers, as a means to mimic the biological self-assembly and organization [9][10][11][12][13][14][15][16][17][18][19][20][21]. Indeed, in these materials, modification of low molar mass polymers with functional groups that associate via H-bonding interactions give rise to a rich variety of self-organizing structures on the mesoscale with a multiplicity of macroscopic properties [22][23][24][25][26][27][28][29][30][31][32][33]. In particular, the nature of the H-bond interactions will largely influence the structure and dynamics of the supramolecular self-assembled structures.…”

Urea Derivatives as Functional Molecules: Supramolecular Capsules, Supramolecular Polymers, Supramolecular Gels, Artificial Hosts, and Catalysts

“…As eries of bis-ureas in which two ureido groups are linked by an aromatic ring or an alkyl group have been widely studied as building blocks fors upramolecularp olymers and gels. [93][94][95][96][97][98][99][100][101] An interesting applicationo fb is-urea LMWGs is supramolecular gel phase crystallization. [96,102] Steed et al achieved crystal growth of pharmaceuticals in as upramolecular gel formed from bis-urea 20 (Figure 16).…”

“…A series of bis‐ureas in which two ureido groups are linked by an aromatic ring or an alkyl group have been widely studied as building blocks for supramolecular polymers and gels [93–101] . An interesting application of bis‐urea LMWGs is supramolecular gel phase crystallization [96, 102] .…”