Supramolecular cross-link

AFM studies on the thin ( 50 nm) brush layers demonstrate that the dynamics of supramolecular cross-links contribute to the friction of the soft brush surfaces (Fig. 3.11). When the faster 4a cross-linker is added, both the absolute friction values and the coefficient of friction (COF) drop to 30% of those of the uncross-linked PVP control. When the slower cross-linker 4b is added, however, the absolute friction value and the COF increase dramatically both the COF and the absolute friction values for PVP 4b are more than twice that of PVP alone. The absolute lateral force measured is proportional to the normal force applied this is consistent with the model that the more the tip is pressed into the brush layer the more force it takes to drag it laterally through the brushes. 

Linear Polymeric Supermolecules Supramolecular CROSS-LINKING Self-assembled Dendrimers, ARBOROLS... 

This topology has the potential for a high degree of supramolecular cross-linking. 

Reaction of calixarene (47) and CO2 is special, because it converts linear supramolecular polymeric chains (48) into supramolecular, 3D polymeric networks (46). These are also switchable and can be transformed back to the linear chains (48) without breaking them. While supramolecular cross-linked polymers are known (92), they break upon dissociation of the noncovalent aggregates that compose them. Material 46 is different, as it only releases CO2 and keeps hydrogen-bonding intact. 

The transition between the liquid-crystalline phase and the isotropic state is thermally reversible due to the association and dissociation of hydrogen bonds. Figure 15 presents the thermally reversible formation of the supramolecular cross-linked structures. If these cross-linked structures are prepared only by covalent bonding, no such dynamic reversible behavior is observed. 

Fig. 3 Development of mechanoluminescence as a stress probe within polymeric materials (a) in multiple network elastomers (b) in swollen gels supramolecularly cross-linked with transient metal-ligand bonds and (c) in thermoplastic elastomers. Reprinted with permission from [32] (Copyright AAAS 2014), [33] (Copyright Wiley VCH 2014) and [34] (Copyright American Chemical Society 2014)...

Figure 28 (a) Schematic representation of supramolecular cross-linked networked formed with bismetallic pincer molecule 54 and P4VP. (b) Rheological analysis demonstrating the exact scaling of measured values relative to the dissociation rate of the metal complexes for the viscosity from steady shear measurements. Reproduced from Yount, W. C. Loveless, D. M. Craig, S. L. J. Am. Chem. Soc. 2005, 127,14488-14496. ... 

Figure 6 Various supramolecular cross-linking strategies based on (a) the three-point CA-triazine couple and the six-point CA-isophthalamide (Hamilton wedge) couple (b) ruthenium-terpyridine coordination complexes (c) and (d) the platinum- or palladium-based pincer complexes. ...

Linear polymeric supermolecules - Supramolecular cross-linking - Self-assembled dendrimers, arborols,... 

Figure 19 Schematic representation of supramolecular cross-linking agents of organic and inorganic types, and of the constituting subunits.

A. Pappalardo and coworkers focused on the calix[5]arene/diammonium ion recognition motif for the supramolecular cross-linking of calix[5]arene-tethered poly(p-phenyleneethynylene) covalent polymers 18 [36], Treatment of 18 with 0.5 equiv. of 1,10-decanediyldiammonium dipicrate led to the formation of polycapsular polymeric cross-linked networks, whereas presaturation of the caUxarene cavities with an excess of same guest molecules led to isolated strands of bis-en /o-cavity arrays. Authors were able to show that the cross-linked material withstood several base/acid (Et3N/TFA) promoted disassembly and reassembly cycles. 

Kavitha, A.A. and Singha, N.K. (2009) Tailor-made poly(methyl acrylate) bearing amantadine functionality (amino adamanty 1) via atom transfer radical polymerization (ATRP). A precursor of a supramolecular cross-linked polymer. Macromolecules, 42,5499-5508. 

Appel, E.A., Biedermann, F., Rauwald, U., Jones, S.T., Zayed, J.M., Scherman, O.A. Supramolecular cross-linked networks via host—guest complexation with cucurbit[8]uiil. J. Am. Chem. Soc. 132(40), 14251-14260 (2010)... 

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