Diels-Alder Click Reactions

Diels-Alder dick reaction, (a) Backbone mod- MMA) copolymers by Diels-Alder dick reac-ification with tetracyano ethylene (r.t., 48h) tion (110°C, 48h, toluene) [38]. 

A special feature of olefin metathesis polymerization is that the unsaturation of the monomer is retained in the course of the reaction. Thus, thiol- ene click chemistry can be directly applied at the polymeric backbone for attaching functional moieties [44, 61]. The reaction proceeds under irradiation of UV hght (254, 365, 

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Figure 14 The first examples of click reactions explored for dendrimer synthesis (a) CuAAC click reaction (b) Diels-Alder click reaction and (c) thiol-ene click reaction...

Diels-Alder click reaction for the synthesis of star block copolymers consisting of PSt-PMMA arms. This so-called double click strategy is summarized in Scheme 71. 

Figure 12.20 Diels-Alder click reactions of maleimide with (a) furan and (b) anthracene.

Scheme P12.10.1 Diels-Alder click reactions in the synthesis of (a) PMMA-i>-PSt, (b) PEG-h-PSt, and (c) PMMA-(>-PEG copolymers. (Adapted from Durmaz, Colakoglu, Tunca, and Hizal, 2006.)...

Scheme P12.11.1 Schematic presentation of grafting process by Diels-Alder click reaction. (Adapted from Gacal, Durmaz, Tasdelen, Hizal, Tunca, Yagci, and Damirel, 2006.)...

Diels-Alder click reactions have been successfully used for the preparation of well-de ned star polymers. Devise methodologies using this route to prepare 3-arm star polymers with uniform arms, core-As, where A is (a) poly(ethylene glycol), (b) poly(methyl methacrylate), and (c) poly(tert-butyl... 

Scheme 9.1 Overview of click type reactions. (a) Azide/alkyne click reaction, (b) nitrile oxide cycloaddition, (c) Diels-Alder click reaction, for example, reaction of...

The anthracene group, required for Diels-Alder click reaction, is compatible with the ruthenium catalyst and can be introduced directly within the monomer... 

Tunca et al. [27, 28,38] reported in a series of papers on a multi-click approach for the preparation of brush copolymers. The backbone consisted of homopolymers, statistical polymers, or block copolymers from ONBEs with orthogonal side groups for Diels-Alder click reaction [27,28,38], azide/alkyne click reaction, [27, 28, 38] and nitroxide coupling [27]. In a grafting-to approach, maleimide-or ONBE-functionalized polymers (PEG, P BA, PMMA (56)) were attached by Diels-Alder click reaction with the anthracene groups pendant at the polymer backbone (55) (Scheme 9.8b). PCL chains were attached by an azide/alkyne click reaction, while a combination of Diels-Alder and azide/alkyne click reaction allowed the synthesis of graft copolymers with PS-/ -PEG-, PS-h-PMMA-, or PS-/ -P BA side chains. 

Dag, A., Durmaz, H., Thnca, U., and Hizal, G. (2009) Multiarm star block copolymers via Diels-Alder click reaction. Journal of Polymer Science Part A-Polymer Chemistry, XI, 178. 

Recently, a new strategy toward the synthesis of dendronized polymers via Diels-Alder click reaction was designed by Sanyal and coworkers (Tonga et al, 2010). First, a styrene-based... 

Diels-Alder Click Reaction for the Synthesis of Star-Shaped Polymers... 

In addition to the broad application of the CuAAC reaction, other types of highly efficient click reactions were used for the synthesis of star-shaped polymers. Tunca and coworkers used the Diels-Alder click reaction for the preparation of 3-arm star-shaped polymers using furan protected maleimide end-fiinctionalized PEO, PMMA or PtBuA and trianthracene functional linking agents (Dag et al., 2008). However, the resulting yields are comprised between 82 and 93% depending on the coupled polymer, the reaction conditions are more drastic than those used in CuAAC. 

The same group also reported on the synthesis of multiarm star block copolymers by using Diels-Alder cycloaddition reactions (Dag et al., 2009). First, an a-anthracene-end functionalized PS (PS-anthr) and furan-protected maleimide-end-functionaUzed polymers, including PMMA and PtBuA, were prepared via ATRP. The maleimide functionalities were protected as they can contribute to the copolymerization with MMA or tBuA. Moreover, the polymerization temperature was kept below 60 °C to prevent deprotection during the polymerization. In the next step, a 33-arm anthracene-end functionalized (PS) star polymer was obtained using PS-anthr as macroinitiator and divinyl benzene as crosslinker. These star polymers were then reacted with the unprotected maleimide end-functionalized PMMA or PtBuA to give multiarm star block copolymers via Diels-Alder click reaction. The efficiencies were foimd to be 96 and 88%, respectively. 

Tasdelen MA (2011) Diels-Alder click reactions recent applications in polymer and material science. Polym Chem 2 2133-2145... 

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