Copolymeric dendrimers

Dvornic, P. R., de Leuze-Jallouli, A. M., Owen, M. J. and Perz, S. V. Radially layered poly(amidoamine-organosilicon) (PAMAMOS) copolymeric dendrimers in Clarson, S. J., Owen, M. J., Fitzgerald, J. J., Smith, S. D. (eds.), Silicones and Silicone-Modified Materials, ACS Symposium Series, Vol. 729, American Chemical Society, Washington, DC, 2000, pp. 241-269. 

In some applications it is useful to have hydrophilicity in the bulk of the polymer instead of just at the surface. One way of doing this is by simultaneously end linking hydrophilic poly(ethylene glycol) (PEG) chains and hydrophobic PDMS chains. Another way is to make a PDMS network with a trifunctional organosilane R Si(OR)3 end linker that contains a hydrophilic R side chain, such as a polyoxide. Treating only the surfaces is another possibility, for example, by adding hydrophilic brushes by vapor deposition/hydrolysis cycles.Such hydrophilic polysiloxanes can also serve as surfactants. It has also been possible to make radially layered copolymeric dendrimers with hydrophilic polyamidoamine interiors and hydrophobic organosilicon exteriors. " ... 

Radially Layered Poly(amidoamine-organosilicon) Copolymeric Dendrimers and Their Networks Containing Controlled Hydrophilic and Hydrophobic Nanoscopic Domains... 

Figure 1 Schematic representation of homopolymeric (A) and two types or ordered copolymeric dendrimers radially layered (B) and segmented (C) ones. Small circles denote the branch junctures, larger circles represent the branch cells, while numerals indicate dendrimer generation layers and each Z is an end-group. Note that copolymeric dendrimers are composed of at least two different compositional types of branch cells (1 and 2).

The synthesis of radially layered poly(amidoamine-organosilicon) (PAMAMOS) copolymeric dendrimers starts from amine terminated PAMAM dendrimers, which, in turn, are obtained by a well-known excess-reagent divergent growth method that involves a reiterative sequence of (a) Michael addition reactions of methyl acrylate (MA) to primary amines, and (b) amidation of the resulting methyl ester intermediates with ethylenediamine (EDA), as shown in Reaction Scheme 1 (39-41). These PAMAM dendrimers are commercially obtained from Dendritech Inc., (Midland, MI) and they can be used for PAMAMOS preparation without any further purification. The synthesis then involves another Michael addition reaction, this time of a silylated acryl ester, such as (3-acryloxypropyl)dimethoxymethylsilane, as shown in Reaction Scheme 2 (4). 

Vinylphenyl-terminated PBE dendrons were prepared as polymerizable den-drons from 4-vinylbenzyl chloride [37]. The vinylphenyl-terminated PBE dendrons are useful to make the lanthanide-cored dendrimer complexes polymerizable. The Ist-generation Tb +-cored dendrimer complex bearing the vinyl-phenyl terminal on the dendron subunits (Fig. 5) was copolymerized with N-iso-propylacrylamide in the presence of methylene bis-acrylamide (as crosslinker) in DMSO to give a green-luminescence transparent gel. The DMSO gel was con-... 

Polymerization hybrids are obtained by the polymerization of a linear chain initiated from the focal point of a convergent dendrimer or the chain ends of a dendrimer, or by polymerization or copolymerization of a dendronized monomer. 

Kawa M, Takahagi T (2004) Improved antenna effect of terbium(III)-cored dendrimer complex and green-luminescent hydrogel by radical copolymerization. Chem Mater 16 2282-2286... 

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... 

Different architectures, such as block copolymers, crosslinked microparticles, hyperbranched polymers and dendrimers, have emerged (Fig. 7.11). Crosslinked microparticles ( microgels ) can be described as polymer particles with sizes in the submicrometer range and with particular characteristics, such as permanent shape, surface area, and solubility. The use of dispersion/emulsion aqueous or nonaqueous copolymerizations of formulations containing adequate concentrations of multifunctional monomers is the most practical and controllable way of manufacturing micro-gel-based systems (Funke et al., 1998). The sizes of CMP prepared in this way vary between 50 and 300 nm. Functional groups are either distributed in the whole CMP or are grafted onto the surface (core-shell, CS particles). 

The combination of an efficient control over the environment of the active sites in a multi-functional catalyst and its immobilization within an insoluble macromolecular support was pioneered by Seebach et al. In their approach, the chiral ligand to be immobilized was placed in the core of a polymerizable dendrimer, followed by copolymerization of the latter with styrene as shown in Scheme 9 [58]. In this way, no further cross-finking agent was necessary, since the dendrimer itself acted as cross-linker. The dendritic branches are thought to act as spacer units, keeping the obstructing polystyrene backbone... 

Since the first report on Ti-TADDOLate-mediated Diels-Alder reactions [97,98] several studies of the same reaction have been reported these have shown that Ti-TADDOLate is an efficient chiral Lewis acid in enantioselective Diels-Alder reactions. Polymer- and dendrimer-supported Ti-TADDOLates have been reported and their catalytic activity in several enantioselective reactions has been evaluated [59]. Various kinds of polymeric TADDOLs were prepared both by chemical modification (Eq. 22) and by copolymerization (Eq. 23). 

The versatility of NPGs has been further enhanced by chemical modifications of the pent-4-enyl moiety itself. In this context, the pentenyl moiety has been transformed in many spacer functionalities [149,150], used as a handle to incorporate amino-acid moieties [151,152,153, 154], used as a monomer in copolymerization strategies [155,156,157], used in the formation of dendrimers [158], and converted to dimeric and trimeric structures for multivalent presentations [159,160]. These applications fall beyond the scope of this chapter. 

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