Starburst poly polymers

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]. 

Hyper-branched starburst poly(siloxysilane) polymers are synthesized through hydrosi-lylation-polymerization of CH2=CHSi(OSiMe2H)3 (269) and HSi(OSiMe2CH=CH2)3 (270). The polymer from 269 has Si—H moieties on the surface of the dendrimer, while that arising from 270 possesses vinyl groups on the outer sphere264. 

Various thiophene-based polymers have been used to improve hole injection in OLEDs such as PTV [346], electrogenerated poly(2,2 -bithiophene) [347], or a starburst-polymer poly(tris[4-(2-thienyl)phenyl]amine 201 [348]. In the last case, an OLED was also reported [349]. Polymer 202 combining the electron-poor phenylquinoline units with dialkylbithiophenes has been proposed as electron-transport material [350,351]. 

Tomalia-type poly(amidoamine) (PAMAM) dendrimers and their use as precise, fundamental building blocks to form poly(dendrimers) or so-called starburst polymers. These poly(dendrimers) are now referred to as megamers [35,36] and are described in more detail later. Other pioneers in the dendritic polymer field include Vogtle, New-kome, Frechet, and others. These historical contributions have been reviewed recently [33],... 

Some attention has arisen to consider dendrimers as building blocks for the construction of nanoarchitectures possessing higher complexity and dimensions beyond the dendrimer. In an early paper, Tomalia et al referred to their starburst polymers as a class of macromolecules obtained from the chemical bridging of starburst dendrimers. These macromolecules have been termed megamers, which have been defined as architectures derived from the combination of two or more dendritic macromolecules or poly(dendrimers). Many examples of randomly assembled as well as structure-controlled megamers have been reported, such as oligomeric covalent assemblies of dendrimers (i.e., dimers, trimers) referred... 

More recently, non-traditional polymerization strategies have evolved to produce a fourth new major polymer architecmral class, now referred to as dendritic polymers [43]. This new architectural polymer class consists of four major subsets (1) random hyperbranched, (2) dendrigrafts, (3) dendrons and (4) dendrimers. Dendrimers, the most extensively studied subset were discovered by the Tomalia group while in The Dow Chemical Company laboratories (1979) and represent the first example of synthetic, macromolecular dendritic architecture [43,44]. First use of the term dendrimer appeared in preprints for the first SPSJ International Polymer Conference, held in Kyoto, Japan in 1984 [45]. The following year, a full article in Polymer Journal [46] (Fig. 8) described the first preparation of a complete family of Tomalia-type poly(amidoamine) (PAMAM) dendrimers (G = 1-7) and their use as precise, fundamental building blocks to form poly (dendrimers) or so-called starburst polymers. These poly(dendrimers) are now referred to as megamers [47, 48] and are described in more detail later in Sect. 6.4.3. Other pioneers in the dendritic polymer field include Vogtle, Newkome, Frechet, Majoral, and others. These historical contributions have been reviewed recently [52]. ... 

Brief definitions of starburst polymers, dendrimers, and dendrons are as follows, and the reader is referred for detailed descriptions to Tomalia s excellent reviews [1]. Starburst is a the trademark name of poly(amide-amine)s, as shown in Scheme 1, and was presented by Tomalia. Recently, dendrimers and dendrons have been defined in general terms for a class of hyperbranched polymers. Dendrimers are systematically constructed to form regularly branched treelike structures. Under ideal conditions, the molecular architecture is very uniform, as shown in Figure 1. A dendron is one of the major subdivisions of a dendrimer. For example. Figure 1 shows the division of a dendrimer into three separate dendrons, labeled A, B, and C. Further subdivisions are also possible, with each of the three dendrons dividing into two subdendrons, each of which then divides into two subdendrons, etc. Thus, one of the major differences between linear polymers and dendrimers is this branched architecture. 

Tomalia presented the synthesis of dendrimers as Starburst polymers, which consisted of poly(amide-amine)s as shown in Scheme 1 [2]. The core molecule in this case was ammonia, and the building block was methylacrylate. First, ammonia reacted with methylacrylate by a Michael-type addition. The obtained ester-terminated molecule was treated with a large excess amount of ethylene-diamine to form amino groups at the terminal positions (generation 0, GO). In this reaction, the methylester is the protected form of the amine, and the treatment with ethylenediamine (ester-amide transformation) corresponds to the deprotection of the ester function. Treatment of this amine-terminated molecule again with methylacrylate results in the formation of another terminal methyl-ester group. The molecule can be extended by repeating these operations. 

Cationic polymer is also frequently examined to increase the potential of a gene drug. Large molecular weight cationic polymers can condense pDNA more efficiently than cationic liposomes. They include poly-L-lysine (PLL), poly-L-omithine, polyethyleneimine (PEI), chitosan, starburst dendrimer and various novel synthetic polymers. These polymers can enhance the cellular uptake of pDNA by nonspecific adsorptive endocytosis. 

Starburst polyacrylamines and their semiconducting complexes as potentially electroactive materials. [H. K. Hall, Jr., D. W. Polis, Polym. Bull. 1987, 77(5), 409-416] [ 604]. 

High-molecular mass surfactants such as butyl acrylate-butyl methacrylate-methacrylic acid copolymer sodium salts, starburst dendrimers, poly(amidoamines), and diaminobutane-based poly(propyleneimine) as well as cationic polyelectrolytes (ionenes) had all been presented as successful secondary phases for aromatic compounds. The determination of 10 nitrophenols in glycine buffers modified by 3-CD (0-10 mmolL" ) and polyvinylpyrrolidone (PVP) (0.5-2.5% w/v) is an example of application of polymer-based electrolytes to rain, tap, and process water. ... 

In 1979, while working for Dow Chemical Co., Donald A. Tomalia discovered Starburst dendrimers, which are poly(amidoamine) (PAMAM) dendrimers prepared by a so-called divergent synthesis [25]. These structures are some of the best characterized and most extensively utilized dendritic polymers in the field of bioscience. Other widely known den-drimer structures are polyethers, which were reported in 1990 by Frdchet [26], and poly(propylene imine) (PPI) dendrimers from the groups of Womer and Miilhaupt [27] and de Brabander-van den Berg and Meijer [28]. Smaller PPI dendrons were described by Vogtle et al. already in 1978 [29]. 

The upper mass range of a polymer that can be analyzed by MALDl-MS is dependent on the polymer type. For example, Danis et al. reported the detection of water-soluble poly(styrenesulfonic acid) with a molecular mass just below 400000 [122], and the detection of a poly(methyl methacrylate) sample with a molecular mass of about 256000 [17]. Multiply charged ions from a starburst polyamidoamine dendrimer with a molecular mass as high as 1.2 milbon has been reported by Savickas [123]. Yalcin et al. showed that polybutadienes of narrow polydispersity with masses up to 300000 Da, and polyisoprenes of narrow polydispersity with masses up to 150 000 Da, can also be analyzed [42]. 

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