Linear hybrid block copolymer

It is also possible to introduce polymerizable groups at the focal point of dendritic macromolecules and a number of authors have demonstrated the synthesis of novel hybrid dendritic-linear block copolymers by this methodology [69-73]. Initial experiments in the use of the dendritic macromonomers involved the preparation of a series of polyether dendrimers, such as the third generation derivative, 37, which contains a single styrene at its focal point [74]. Copolymerization of 37 with styrene then affords a hybrid block copolymer, 38, in which... 

The linear polypeptide hybrid block copolymers and block copolypeptides reported to form vesicles in aqueous solution are listed in Fig. 1. 

The most likely pathways of NCA polymerization are the so-called amine and the activated monomeP (AM) mechanisms. The amine mechanism is a nucleophilic ring-opening chain growth process where the polymer could grow linearly with monomer conversion if side reactions were absent (eqn [2]). On the other hand, the AM mechanism is initiated by deprotonation of an NCA, which then becomes the nucleophile that initiates chain growth (eqn [3]). It is important to note that a polymerization can switch back and forth between the amine and AM mechanisms many times a propagation step for one mechanism is a side reaction for the other, and vice versa. It is because of these side reactions that block copolypeptides and hybrid block copolymers prepared from NCAs using amine initiators have structures different than predicted by monomer feed compositions and most likely have considerable homopolymer contamination. These side reactions also prevent control of chain-end functionality desirable for many applications. 

Gitsov 1, Frechet JMJ. Solution and solid-state properties of hybrid linear-dendritic block copolymers. Macromolecules 1993 26 6536-6546. 

For polymer chemists it is interesting to know how well-known linear polymers can be linked with dendritic architectures and what the supramolecular consequences of this approach might be. Combination of dendrimers with linear polymers in hybrid linear-dendritic block copolymers has been employed to achieve particular self-assembly effects. Block copolymers with a linear polyethylene oxide block and dendritic polybenzylether block form large micellar structures in solution that depend on the size (i.e., the generation) of the dendritic block [10]. Amphiphilic block copolymers have been prepared by the combination of a linear, apolar polystyrene chain with a polar, hydrophilic poly(propylene imine) dendrimer [11] as well as PEO with Boc-substituted poly-a, -L-lysine dendrimers, respectively [12]. Such block copolymers form large spherical and cylindrical micelles in solution and have been described as superamphi-philes and hydra-amphiphiles , respectively. 

The solution properties of hybrid-linear dendritic polyether copolymers are investigated by SEC with coupled viscometric detection from the same authors [12]. The results obtained show that the block copolymers are able to form monomolecular and multimole-cular micelles depending on the dendrimer generation and the concentration in methanol-water (good solvent for the linear blocks). 

Walter, M.V., Lundberg, P., Hult, D., Hult, A., Malkoch, M. A one component methodology for the fabrication of honeycomb films from biocompatible amphiphilic block copolymer hybrids a linear-dendritic-linear twist. Polym. Chem 4, 2680-2690 (2013)... 

In this chapter, attention is focused on novel developments for the production of pristine nucleic acid architectures and DNA-polymer hybrid structures, employing the methods, techniques, and materials acquired from molecular biology. However, while the details of linear DNA block copolymers (DBCs), DNA networks, and catenated DNA structures will be included, the preparation and modification of regular DNA nanostructures, using molecular biology methods and enzymes, will not be discussed as an excellent summary of these procedures is available elsewhere [15]. 

PPE Block Copolymers Jacketed PPEs Water-Soluble PPEs Metu-PPEs Linear and Crossed PPE-PPV Hybrids Organometallic PAEs Thiophene-Containing PAEs Nitrogen Heterocycle-Containing PAEs... 

One of the most popular and effective approaches that has emerged is actually a hybrid between the core-first and the coupling-to routes (see Figure 6). In this strategy, a block copolymer is synthesized so that at the jimction point of the two blocks there is a chemical handle for REO coupling. This handle at the junction is usually an azide or an alkyne and is used to couple the third block, which is a preformed linear... 

T., Hult, A., and Malkoch, M. (2013) Multifunctional Poly(ethylene glycol) synthesis, characterization, and potential applications of dendritic-linear-dendritic block copolymer hybrids. Macromolecules, 46 (10), 3726-3736. 

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