Segmented-block dendrimer

Dendrimers, or arborols, or cascade, or cauliflower, or starburst polymers, were first synthesized in the early 1980s [3,4]. In 1985 Tomalia et al. [5] and Newkome et al. [6] presented the first papers dealing with dendrimers. A multitude of dendrimers have been presented in the literature ranging from polyami-doamine [7,8],poly(propylene imine) [9,10], aromatic polyethers [11-13] and polyesters [14, 15], aUphatic polyethers [16] and polyesters [17], polyalkane [18-19], polyphenylene [20], polysilane [21] to phosphorus [22] dendrimers. Combinations of different monomers as well as architectural modifications have also been presented. For example, chirality has been incorporated in dendrimers [23,24]. Copolymers of linear blocks with dendrimer segments (dendrons) [25-27] and block-copolymers of different dendrons have been described [28]. 

The convergent synthetic strategy is well suited for the production of macro-molecular architectures such as segmented-block dendrimers, which bear either the same or different generations of dendrons, but with different molecular scaffolds linked to a core unit. This type of dendrimer is of interest owing to its multifunctionality. 

Fig. la-f. Types of micellar polymers a block copolymers (macrosurfactants) b stars c graft copolymers d dendrimers e segmented block copolymers f polysoaps... 

Fig. 2a-f. Examples of micellar polymers a block copolymer ( macrosurfactant [25] b star [35] c graft copolymer [36] d dendrimer [44] e segmented block copolymer [56, 57] f polysoap [61-74]... 

Fig. 2. Schematic drawing of layer-block, segment-block, and surface-block dendrimers...

Fig. 3. Schematic drawing of the layered segment-block dendrimer 24-[G 4]2-[G j]...

Following the first papers of Tomalia [178] and Newkome et al. [179] in 1985 dealing with dendrimers, a large number of dendrimers have been presented in the literature ranging from polyamidoamine, aromatic polyethers and polyesters, aliphatic polyethers and polyesters, polypropyleneimine, polyphenylene to polysilane. Copolymers of linear blocks with dendrimer segments (dendrons) and block copolymers of different dendrons have been described. 

FIGURE 5.6 Schematic representation of dendritic copolymers with different polarities (a) segment-block dendrimer and (b) layer-block dendrimer. (From Klajnert, B. and Bryszewska, M., Acta Biochimica Polonica, 48, 199, 2001. With permission.)... 

Polyether-b-polyester dendrimer 3,5-dihydroxybenzyl alcohol as monomer for ether-linked fragments and 2,2,2-trichloroethyl 3,5-dihydroxybenzoate for ester linked fragments radially alternating the dendritic segments produced segmented-block polymer and concentric alternation gave layer-block polymer spectroscopy, thermal characterization described. [269]... 

To obtain segment block dendiimers, Kose et al. (2008) utilized Frechet type dendrons appended with electron rich furan at the focal point and a complementary set of polyester dendrons containing the electron de cient maleimide group at the focal point Combination of these two complimentary dendrons was accomphshed by heating in benzene to obtain thermoresponsive segment block dendrimers in good yields (Hg. 12.27). The dendiimers fell apart upon heating them to 110°C. 

Figure 12.27 Synthesis of thermoresponsive segment-block dendrimers via furan-maleimide DA cycloaddition reaction.

Maraval V, Laurent R, Donnadieu B, Mauzac M, Caminade AM, Majmal JP (2000) Rapid synthesis of phosphoms-containing dendrimers with controlled molecular architectures first example of surface-block, layer-block, and segment-block dendrimers issued from the same dendron. J Am Chem Soc 122 2499-2511... 

Poly(ethylene oxide)-b-poly (L-lysine) dendrimer (PEO-b-dendr PLL) Block copolymer, dendrimer PLL segment Encapsulation of plasmids and oligonucleotides (Choi et al, 1999)... 

In the case of surface-block dendrimers, the dendrimer periphery exhibits different functionalities in specific molecular segments. They are formed by coupling of dendrons differing in the nature of their terminal functionalities to a common core unit (cf. Section 3.2.1) [6, 10]. 

Fig. 3.8 Convergent synthesis of a bifunctionalised dendrimer with two different peripheral groups in separate molecular segments (surface-block dendrimers)...

Surface-block dendrimer with different peripheral groups in separate segments of the molecule. 

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