Copolymer cross-linking negative

For some applications, it is desirable to lock the micellar structure by cross-Hnking one of the micellar compartments, as discussed previously in Sect. 2.6. Cross-Hnked core-shell-corona micelles have been prepared and investigated by several groups as illustrated by the work of Wooley and Ma [278], who reported the cross-linking of PS-PMA-PAA micelles in aqueous solution by amidation of the PAA shell. Very recently, Wooley et al. prepared toroidal block copolymer micelles from similar PS-PMA-PAA copolymers dissolved in a mixture of water, THF, and 2,2-(ethylenedioxy)diethylamine [279]. Under optimized conditions, the toroidal phase was the predominant structure of the amphiphilic triblock copolymer (Fig. 19). The collapse of the negatively charged cylindrical micelles into toroids was found to be driven by the divalent 2,2-(ethylenedioxy)diethylamine cation. 

This approach is known as complex coacervation, and it has also been used for the development of physically cross-linked hydrogels (Farris et al. 2009). Some of the examples in this area are complexes of positively and negatively charged triblock copolymers based on poly(allyl glycidyl ether-hiock-ethylene glycol-hiock-allyl glycidyl ether) (Hunt et al. 2011), polycationic chitosan and polyanionic xanthan (Chellat et al. 2000), protein, and hydrocolloids (Magnin et al. 2004). 

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