Azide terminated

Figure 14.11 Transfer printing of DNA and RNA using dendri-stamps.101,102 A PDMS stamp is oxidized and coated with a PPI dendrimer. DNA or RNA binds to the dendrimer-coated stamp in a layer-by-layer arrangement. If the DNA (or RNA) is functionalized with an alkyne, it can be printed on an azide-terminated self-assembled monolayer. If the DNA (or RNA) is functionalized with an amine, it can be printed on an aldehyde-terminated self-assembled monolayer. (See color insert.)...

Mehdinia A, Habib Kazemi S, Zahra Bathaie S et al (2008) Electrochemical smdies of DNA immobilization onto the azide terminated monolayers and its interaction with taxol. Anal Biochem 375(2) 331-338... 

The latter material was then added to a solution of the second azide-terminated polymer to produce three-miktoarm star polymers in excellent yields. 

On the contrary, better results were obtained for the synthesis of the miktoarm stars PS(PDMAEMA)2. A mixture of the azide-terminated polymers and the coupling agent, TPTTA, in a molar ratio [PS-N3] [PDMAEMA-N3] [TPTrA] = 1 5 1 were reacted in the presence of CuCl/PMDETA at 70 C, leading to the formation of a mixture of the desired miktoarm star PS (PDMAEMA)2, the 3-arm star (PDMAEMA)3, and the excess PDMAEMA arm (Scheme 45). The miktoarm star was isolated by selective precipitation in methanol/water (v/v= 1/1). 

There are, however, caveats that should be considered for each of the aforementioned approaches. It has been shown that aminolysis of RAFT end groups can lead to disulfide or even cyclic by-products depending on the polymer repeat unit so generally aminolysis and TEC are done in a one-pot reaction to avoid these deleterious reactions. With respect to azide-terminated polymers obtained by displacement of... 

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... 

Scheme 7.12 One-pot two-step synthesis which converts sulfonyl azides, terminal alkynes, and nitriles into imidazoles. The only byproduct of the reaction is a molecule of dinitrogen.

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.

Figure 12.13 Synthesis of generation 2 dendrimer (azide-terminated) by CuAAC reaction using a divergent approach. (After Joralemon et al., 2005. With permission from American Chemical Society.)...

Figure 12.14 Synthesis of generation 3 dendrimer (azide-terminated) by CuAAC reactions using a divergent...

Though typically a stepwise procedure was used in which the azide-terminatred polymer was isolated and puri ed before reaction with the alkyne species, an in-situ end group transformation process was also condncted in both the cases in which the azide-terminated polymers were reacted in situ with alkyne-functionahzed methacrylates. This one-pot synthesis is possible due to the orthogonal reactivity inherent in chck chemistry. 

The combination of ATRP and postpolymerization modi cation by CuAAC click chemistry can be employed to prepare well-de ned tu-(meth)acryloyl macromonomers in an ef cient manner. Thus, polystyrene (PSt) can be prepared by ATRP and subsequently derivatized to contain azide end groups. The azide-terminated polymers can then be reacted with alkyne-containing (meth)acrylate monomers to achieve near-quantitative chain-end functionalization by CuAAC reaction. An ef cient synthesis route is shown in Scheme P12.1.1. 

Scheme P12.2.1 Synthesis of a-alkyne-w-azide-terminated polystyrene (PSt) of high molecular weight by the method of Tsarevsky et al., 2005.

Scheme P12.3.2 Outline for the synthesis of o -(TIPS-acetylene)-a -azide terminated polystyrene. (Drawn following the synthesis method of Opsteen and Van Hest, 2007.)...

Jia and coworkers took advantage of CuAAC to design an elastin-like peptide-polymer conjugate. The reaction between a bifunctional, azide-terminated PEO block and an alkyne-functionalized peptide composed of two different functional domains yielded a multiblock copolymer (Figure 1.12). 

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 . 

Upper rim appended hybrid calixarenes are obtained from azide terminated calixarenes and alkyne terminated polymers... 

The RAFT polymerization of a -azido- u-dithiopyridine affords azide-terminated het-erotelechelic polymers which were reacted with biotin/avidine glutathion and bovin serum albumine via click and thiol-disulflde exchange reactions... 

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