Polymers self-sorting

Scheme 4.18 Self-sorting noncovalent functionalization of a universal polymer backbone.

Multiple Hydrogen Bonding Interactions Self-Sorting on Polymers... 

The selective self-assembly of a receptor molecule with its complementary recognition unit in the presence of a competitive recognition unit has been described as self-sorting in the literature. DNA and RNA are the prime examples of this concept. Using the above-described copolymers containing two hydrogenbonding units, Burd and Week [95] were able to prove this concept of self-sorting also in synthetic polymer systems (Fig. 7.22). 

Burd, C., and Week, M. 2005. Self-sorting in polymers. Macromolecules 38 7225-7230. Celiz, A. D., and Scherman, O. A. 2008. Controlled ring-opening polymerization initiated via self-complementary hydrogen-bonding units. Macromolecules 41 4115-4119. 

Self-sorting under kinetic control has also been reported [75]. However, due to the dynamic nature of the noncovalent interactions used in polymer self-assembly, the products of self-sorting usually cannot be isolated when they form in solution. 

Self-sorting in polymers is not only of interest for multifunctionalization of polymers. Pollino et al. have shown that both functionalization and cross-linking can be done noncovalently in one step/pot by using the orthogonal assembly of palladium pincers with pyridine groups and thymine groups with diaminopyridine groups [94]. 

Similarly, Wasserman and coworkers have studied a wide selection of polymeric materials in aqueous solution that are associative of some kind, i.e., that form some sort of self-assembly through non-covalent interactions [96]. Their study mainly deals with hydrogels of hydrophobically modified polymers, aqueous solutions of polymeric micelles created by block copolymers, and hydrogels based on poly (acrylic acid) and macrodiisocyanates. The spin probes of choice were hydrophobic, such as 5- and 16-DSA (see Eig. 2) or even spin labeled polymers. It was, e.g., possible to screen for the effect of chemical stmcture on the gel formation by recording and understanding the local mobility of the hydrophobic, long chain spin probes as a function of temperature. 

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