Dendritic-linear copolymer hybrid

Hybridization of Architectural States Dendritic-linear Copolymer Hybrids... 

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. 

In the example above, the key role of the dendritic architecture is to act as a multivalent crossUnking imit in the formation of the gel-phase materials. Gitsov and Zhu have also utiUsed a similar approach to the appHcation of dendritic architectures. They reacted Fr chet-type dendritic benzyl bromides and polyethylene glycol to generate hybrid covdently crosshnked dendritic-linear copolymers, which acted as hydrogels [49]. 

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... 

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)... 

Emrick, T., Hayes, W., and Frechet, J. M. J. (1999). A TEMPO-mediated living free-radical approach to ABA triblock dendritic linear hybrid copolymers. J. Polym. Sci., Part A Polym. Chem., 57(20) 3748-3755. 

Some of the hybrid linear-dendritic block copolymers have been subjected to a thorough characterization in solution [48,55] and in the solid state... 

In order to explore the properties that may be obtained by hybridizing the linear and dendritic architectural states, both diblock and triblock copolymer... 

As this brief overview demonstrates, novel copolymers obtained by hybridization of the linear and globular architectural states are readily prepared through a variety of synthetic approaches. In general the dendritic components of the hybrid copolymers are well defined, with unique molecular and structural characteristics. In contrast, all the linear components prepared polymerization are less precisely defined and are polydisperse. Only the very short linear components, themselves prepared by stepwise synthesis just like the dendrons, are monodisperse and can be used to prepare well-defined, monodisperse hybrids. While architectural and structural precision may be of great importance for the determination of ultimate properties, some degree of structural variation is quite acceptable for practical applications in many areas including, for example, surface modification, sensing, or encapsulated delivery. 

Because linear and dendritic polymers have very different physical properties and intermolecular interactions, copolymers of these two macromolecular architectures are expected to exhibit interesting behavior. Gitsov et al. first synthesized these polymeric hybrids by reacting one or both hydroxyl... 

Cylindrical, rod-shaped dendrimer assemblies were first synthesized by TomaUa et al. as early as 1987 [35,37,177]. These structures represent some of the first examples of hybridized dendritic architecture. Since they possess a linear polymeric core and dendritic arms, they are called architectural copolymers or dendronized, linear polymers. This work was recently reported in detail [160]. The method involved the divergent dendronization of //near poly(ethyleneimine) (PEI) cores... 

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