Supramolecular polymers based on the quadruplex formation of ditopic guanosine macromonomers in nonaqueous media

Reversible organogels triggered by dynamic K+ binding and release

In this study, a new lipophilic guanosine derivative was synthesized as an organogelator. The self-aggregation behavior of this organogelator was investigated by NMR, XRD and AFM. In solution, the lipophilic guanosine derivative can form a stable ribbon-like structure through NH(1)-N(7) and NH(2)-O(6) hydrogen bonds. However, gelation would occur in some aprotic solvents after the concentration reached a definite value. More interesting, the ribbon-like structure was able to change to G-quartets in the presence of K(+), which led to the transformation from a gel to a sol. Upon the addition of the cryptand [2.2.2], which can efficiently complex with K(+), G-quartets reverted to the original ribbon-like structure and the gel recovered. Subsequently, upon the addition of acids, K(+) was released from the cryptate with the transformation of gel-to-sol simultaneously. Finally, upon the addition of bases which deprotonated [H(+) ⊂ 2.2.2], the liberated cryptand [2.2.2] recaptured K(+) and the gel was regenerated again. This process of interconversion between G-ribbon 1(n) and octamer 1(8)·K(+) was well monitored by circular dichroism spectra.

Base-pairing mediated non-covalent polymers

The naturally occurring nucleic acid bases (nucleobases) adenine, thymine (uracil), guanine, and cytosine are widely appreciated for their ability to stabilize canonical Watson-Crick base-pairing motifs, as well as a number of other well-characterized arrangements, such as Hoogsteen and wobble heterodimers, and a variety of homodimers. In this tutorial review, the use of these kinds of interactions to form synthetic polymeric and oligomeric ensembles is summarized. Particular emphasis will be placed on synthetic analogues of guanine that stabilize the formation of well-defined higher order aggregates, as well as de novo polymeric systems whose properties are modulated by the presence of nucleobase derivatives incorporated within or attached to the chain-defining backbone. In both cases, nucleobase-nucleobase interactions serve to underlie the chemistry, establish the structural morphology, and enable the development of bioinspired, environmentally responsive materials.

Challenges and breakthroughs in recent research on self-assembly

The controlled fabrication of nanometer-scale objects is without doubt one of the central issues in current science and technology. However, existing fabrication techniques suffer from several disadvantages including size-restrictions and a general paucity of applicable materials. Because of this, the development of alternative approaches based on supramolecular self-assembly processes is anticipated as a breakthrough methodology. This review article aims to comprehensively summarize the salient aspects of self-assembly through the introduction of the recent challenges and breakthroughs in three categories: (i) types of self-assembly in bulk media; (ii) types of components for self-assembly in bulk media; and (iii) self-assembly at interfaces.