Click chemistry copolymers

Liu et al. reported the preparation of two types of shell-cross-linked (SCL) micelles with inverted structures via click chemistry starting from a well-defined schizophrenic water-soluble triblock copolymer in purely aqueous solution. They present an efficient synthesis of two types of SCL micelles with either pH- or temperature-sensitive cores from a novel poly(2-(2-methoxyethoxy) ethyl methacrylate)-ft-poly(2-(dimethylamino) ethyl methacrylate)-Z -poly(2-(diethylamino) ethyl methacrylate) [PME02MA-ft-P(DMA-co-QDMA)- -PDEA] triblock copolymer. First, PMEO2MA- -PDMA- -PDEA was prepared and the DMA blocks were partially converted to a quaternized DMA (QDMA) block with click-cross-linkable moieties to form novel schizophrenic water-soluble triblock copolymers. The pH- or temperature-induced micellization and subsequent shell cross-linking of the P(DMA-co-QDMA) inner shell with the tetra-(ethylene glycol) diazide via click chemistry resulted in nanogel networks (Figure 54.14). 

Jiang, X. Zhang, G. Narain, R. Liu, S.H. Fabrication of two types of shell-cross-linked micelles with Inverted structures in aqueous solution from schizophrenic water-soluble ABC triblock copolymer via click chemistry. Langmuir 2009, 25 (4), 2046-2054. 

X. Pang, L. Zhao, C. Feng, Z. Lin, Novel Amphiphilic Multiarm, Starhke Coil-Rod Diblock Copolymers via a Combination of Click Chemistry with Living Polymerization. Macromolecules 2011,44,7176-7183. 

Degradable brush PHEMA-PDMAEMA-based copolymers were prepared by a combination of ATRP and click chemistty. Click chemistry introduced by Sharpless et al. is one of the most widely used approaches to prepare well-controlled macromolecules and biomolecules. " An azido-modified ATRP initiator was used to prepare PDMAEMA. PHEMA prepared by ATRP was modified with carbonyldiimidazole (CDI)-activated PDMAEMA. The click reaction between two polymers yielded brush polymers of varying molecular weights (Scheme 3.11). A brush copolymer of PDMAEMA of 50 kDa showed high p-galactosidase expression in Cos-7 cells, compared to analogues of other molecular weights. ... 

Recently, well-defined AB2 dual (temperature and pH) sensitive miktoarm star copolymers of (PNIPAm)-(PLL)2 were synthesized through the combination of ATRP, ROP and click chemistry. " Propargylamine was used to initiate ROP of ZLL-NCA for the preparation of all nyl-terminated polypeptide. The use of a diazide-functional ATRP initiator afforded PNIPAm with two azide groups at the chain end. The subsequent click reaction led to the formation of a (PNIPAm)-(PZLL)2 star. The final double hydrophilic structure was obtained after deprotection of the polypeptide arms. 

Among these reactions, the Cu(l)-catalyzed azide-alkyne cycloaddition (CuAAC) is the most widely used. This reaction has been implemented for the preparation of segmented block copolymers from polymerizable monomers by different mechanisms. For example, Opsteen and van Hest [22] successfully prepared poly(ethylene oxide)-b-poly(methyl methacrylate) (PEO-b-PMMA) and PEO-b-PSt by using azide and alkyne end-functionalized homopolymers as the click reaction components (Scheme 11.2). Here, PEO, PSt, and PMMA homopolymers were obtained via living anionic ring-opening polymerization (AROP), atom transfer radical polymerization (ATRP), and postmodification reactions. Several research groups have demonstrated the combination of different polymerization techniques via CuAAC click chemistry, in the synthesis of poly(e-caprolactone)-b-poly(vinyl alcohol) (PCL-b-PVA)... 

Bria et al. synthesized a tetracationic cyclophane-aromatic crown ether-type side-chain poly[2]catenane 59 by employing click chemistry, via route iii (Scheme 17.18) [111]. First, the template-directed coupling reaction between bis(bipyridinium) salt 28 and the alkyne-substituted p-xylylene dibromide 55, in the presence of dinaphtho crown ether 54, afforded an alkyne-functionalized [2]catenane 56 [112], Substitution of the chloro group on styrene-vinylbenzyl chloride copolymer 57 (M = 3.7 kDa, M , = 6.3 kDa) with sodium azide gave the azide-functionalized polymer 58 [83,113-115]. By employing CuS04/ascorbic acid as catalyst [116-120], click chemistry between azide-functionaUzed polymer 58 and alkyne-functionalized [2]catenane 56 afforded the side-chain poly[2]catenane 59, the successful formation of which was confirmed with Fourier transform infrared (FTIR) and NMR analyses. Unfortunately, both of these techniques revealed that the reaction of the azide groups was incomplete, and the observation was ascribed to a Coulombic repulsion of the cyclophane units and steric hindrance caused by the bulky catenane units[121]. 

The use of click chemistry has also influenced the construction of more sophisticated star polymers, such as those with block copolymer arms. Maty-jaszewski has eloquently demonstrated the preparation of three-arm star block copolymers by again combining ATRP with CuAAC click couphng [109]. In these studies the ATRP of styrene, starting from a trifunctional initiator, yielded the three-arm star homopolymer bearing bromide end groups that subsequently were transformed by substitution with sodium azide. CuAAC reaction with PEO-alkyne... 

Living cationic polymerization can be also transformed to RAFT polymerization to synthesize well-defined block copolymers. Very recently, PIB-CTA was prepared by site transformation of hydoxyl-terminated PIB, which was obtained by living cationic polymerization of IB using the TMPCl/TiCU initiation system and subsequent conversion of chlorides into hydroxyl groups. Consequently, RAFT polymerization of MMA or St was mediated by the PIB-CTA resulting in AB block copolymers with narrow polydispersities (Scheme 55). In a very similar report, the PIB-CTA was prepared via click chemistry rather than esterification reaction and used in the polymerization of NIPAM yielding PIB-b-PNIPAM. " ... 

Click chemistry has been considered as a useful synthetic methodology and has been applied to macromolecular chemistry, offering materials ranging from block copolymers to complex macromolecular structures. ... 

Temperature and pH were used in combination to modify the assembly of a double hydrophilic Janus-type A7B14 miktoarm star block copolymer. Click chemistry and ATRP were combined to prepare stars with 7 poIy(diethyIaminoethyI... 

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