Azide-terminated poly

More often the click reaction is used in the modification of biopolymers. An example is sugar-derived imaging in live animals. Glycans in live zebrafish embryos light up when the embryos are fed azide-derived sugars and are subsequently treated with difluori-nated cyclooctyne derived probes. Elastin-like hybrid polymers, based on the reaction of azide-terminated poly (ethylene oxide) (PEG) and alkyne functionalized peptides, are also developed. These polymers are intended to grow new vocal cords . 

The earliest example of block copolymers made using CuAAC was from Opsteen and van Hest in 2005, when they coupled alkyne-terminated polymer with azide-terminated polymer in excellent yields to make several diblocks (see Scheme 4). While this example was an excellent proof of concept, the polymers formed (PS-PMMA, PS-poly(ethylene oxide (PEO), PMMA-PEO) can easily be synthesized by sequential CFR polymerizations, or by the use of PEO-based macroinitiators. It has, though, served as a template for researchers to use CuAAC to make block copolymers that might be prohibitively difficult or impossible to synthesize with only previously existing polymerization techniques. For... 

Figure 12.8 Schematic representation of (a) step-growth coupling of bivalent azide and bivalent acetylene telechelic polymers (b) polymer modi cation by CuAAC of pendant alkyne groups of polymers, e.g., poly(vinyl acetylene), with an azide-bearing substrate and (c) functionalization of polymer by CuAAC of pendant azide with alkyne-bearing functional moiety. Azide terminated dendrimers are similarly subjected to CuAAC with alkyne-derivatized functional moieties to achieve desired functionalization of dendritic macromolecules.

In a similar convergent strategy, the Monteiro group have demonstrated the preparation of well-defined, three-miktoarm star polymers using a combination of ATRP and CuAAC [108]. As discussed previously, polymers prepared via ATRP can be easily transformed by a nucleophihc displacement of the terminal halides with sodium azide to yield cUck -functional materials. In this way, PS, poly(t-butyl acrylate) (PtBA), and poly(methyl acrylate) (PMA), all of which bore a terminal azide... 

Stimuli responsive flexible chains have been combined with fluorine-based rods. A thermally responsive rod-coil poly[poly (N-isopropylaaylamide)-f7-PF-b-poly(N-isopropylacrylamide)] triblock copolymer has been successfully synthesized through ATRP from an end-functionalized macroinitiator. The multifunctional sensory properties of amphiphilic poly[2,7-(9,9-dihexylfluorene)]-Mocfe-poly[2-(dimethylamino)ethyl methacrylate] (PF-1 -PDMAEMA) rod-coil diblock copolymers were reported for different PDMAEMA coil lengths. Thermoresponsive conjugated rod-coil-coil triblock copolymers were prepared from terminal azido-functionalized poly(N-iso-propylacrylamide)-b-poly(N-hydroxyethylacrylamide) (PNIPAAm-b-PHEAA) and alkynyl-functionalized PF via a click reaction. The azido-functionalized PNIPAAm- 7-PHEAA copolymers with different block ratios were prepared by ATRP from an initiator bearing the azide group, whereas alkynyl-functionalized PF was synthesized by Suzuki coupling. ... 

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