Dendritic-linear copolymers

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

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]. 

Linear-dendritic star copolymers [5], most frequently obtained via processes in which dendrimers function as multifunctional initiator cores for the poly-... 

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 broad applicability of ATRP in the ionic liquid [BMIMjPFg was shown by extending it to the polymerization of N-substituted maleimides with styrene. The ATRP was initiated with dendritic polyaryl ether 2-bromoisobutyrate as the initiator at room temperature. The dendritic-linear block copolymers formed in the ionic liquid were characterized by low polydispersity (1.05chain-extension polymerization, suggesting the living nature of the polymerization 247). 

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

Nguyen PM, Hammond PT. Amphiphilic linear-dendritic triblock copolymers composed of poly(amidoamine) and poly(propylene oxide) and their micellar-phase and encapsulation properties. Langmuir 2006 22 7825-7832. 

Table 4.5 Limiting area per molecule from extrapolation of the condensed-phase region of the isotherms for the modified linear-dendritic diblock copolymers. (From ref. [112])...

Figure 5.2. Linear dendritic triblock copolymers prepared via anion trapping with benzyl bromide focal groups.

Kim and coworkers observed the formation of micelles in aqueous solutions by synthesizing a amphiphilic linear-dendritic diblock copolymer based on poly(ethylene oxide) (PEO) (Figure 5)50,62. In this case, the PEO can be considered as the core upon which the dendrimer was synthesized via a divergent process. In an aqueous phase, the hydrophilic... 

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. 

Yu, D. Vladimirov, N. Erechet, J.M.J. MALDI-TOE in the characterizations of dendritic-linear block copolymers and stars. Macromolecules 1999, 32, 5186-5192. 

Gitsov and Frechet [11] reported the syntheses of novel linear-dendritic triblock copolymers achieved via anionic polymerization of styrene and final quenching with reactive dendrimers. For the characterization of the products in the reaction mixture, SEC with double detection was performed at 45°C on a chromatography line consisting of a 510 pump, a U6K universal injector, three Ultrastyragel columns with... 

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). 

Unique dendritic—linear block copolymers have also been prepared by the coupling of functionalized initiators with dendritic macromolecules prepared by the convergent growth approach.194 In these ap-... 

PEO prepared by anionic polymerization using the monofunctional initiator ((diphenylmethyl)potassium) has one -OH end group leading to the formation of linear-dendritic diblock copolymers (Scheme 102). 

---