Polymers dendritic

DSM has commercialized new dendritic (highly branched) polymers, under the name Hyhrane. Related to the original dendrimer. Astramol, these performance additives are described as hyperbranched . They do not require such a perfect structure as a dendrimer, but they generally retain many of the properties characteristic of these materials. 

The use of dendritic cores in star polymer synthesis by NMP, ATRP and RAFT polymerization was mentioned in Section 9.9.1, In this section wc describe the synthesis of multi-generation dendritic polymers by an iterative approach. 

Percec et developed what they termed the TERMINI approach to 

Graft copolymers made by living polymerization processes are often called polymer brushes because of the uniformity in graft length that is possible. The basic approaches to graft copolymers also have some analogies with those used in making block and star copolymers. 

Examples of pol5nners with dendrimer structures include amide amine dendrimers and phenyl ether dendrimers. The terminal amino group of an amide amine dendrimer may be allowed to react with acrylic acid derivatives or methacryUc acid derivatives to S)mthesize amide amine dendrimers having terminals of acrylic or methacrylic acid derivatives (44). 

Another synthesis route of a dendrimer is as follows (44) 3,5-Di-hydroxybenzyl alcohol is allowed to react with 3,5-diphenoxybenzyl bromide to synthesize a second generation benzyl alcohol. The OH group of the benzyl alcohol is replaced with Br using CBri and tri-phenylphosphine, and then the product is allowed to react with 3,5-dihydroxybenzyl alcohol to S5mthesize a next generation benzyl alcohol. The same reaction is repeated to S5mthesize the desired 

In the synthesis of a dendrimer an alkyl halide is used as an alternative to benzyl bromide to produce a phenyl ether dendrimer having a terminal structure including the corresponding alkyl group (45). Also, polyamine dendrimers can be used (46). 

A photocurable ink composition that contains a dendrimer has been described. The dendritic polymer has a molecule structure in which a functional group is dense on the surface with high density in comparison to a linear polymer. 

However, if the dendritic polymer is added to the ink composition, the viscosity of an ink is significantly increased and discharge failures of the inkjet head may occur (48). 

Synthesis Controlled, stepwise growth Single-step polycondensation 

Crystallinity Non-crystalline, amorphous Semi-crystalline/crystalline 

Although we have described the growth of dendritic polymers as being highly controllable, the resultant size of the polymer is mathematically limited. This is in direct contrast to linear polymers that may increase in size to infinity (as long as they 

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J.M.J. Frechet (C. J. Hawker, 1990) replaced the divergent synthesis by a convergent growth of a dendritic polymer. The repeatedly employed monomer, 5-hydroxymethyl-l, 3-benzenediol, was 1,3-O-dibenzylatcd with 3,5-bis(benzyloxy)benzyl bromide. The resulting benzyl alcohol containing 7 benzene rings was converted to the benzyl bromide which was... 

The first steps of a second process for divergent synthesis of dendritic polymers by ATRP are shown in Scheme 9.73.12S In this case, a caiixarcnc core... 

Due to dieir compact, branched structure and to die resulting lack of chain entanglement, dendritic polymers exhibit much lower melt and solution viscosity dian their lineal" counterparts. Low a-values in die Mark-Houwink-Sakurada intrinsic viscosity-molar mass equation have been reported for hyperbranched polyesters.198 199 Dendrimers do not obey diis equation, a maximum being observed in die corresponding log-log viscosity-molar mass curves.200 The lack of chain entanglements, which are responsible for most of the polymer mechanical properties, also explains why hyperbranched polymers cannot be used as diermoplastics for structural applications. Aldiough some crystalline or liquid... 

J.M.J. Frechet and D. TomaUa, Dendrimers and Other Dendritic Polymers, Wiley, Chichester, 2001. 

Muscat D, van Benthem RATM (2001) Hyperbranched Polyesteramides - New Dendritic Polymers. 212 41-80... 

JMJ Frechet, DA Tomalia (2001) Dendrimers and other Dendritic Polymers. Wiley, Chichester, UK. GR Newkome, CN Moorefield, F VBgtle (2001) Dendrimers and Dendrons. Wiley-VCH,Weinheim, Germany. 

Figure 14 rr-Conjugated dendritic polymers (18 and 19) obtained from tri-9-anthrylborane. The branched conducting polymer 20 was obtained from tris(JV-pyrrolyl)borane. (Adapted from refs. 38 and 39.)... 

Chapman et al. [131] reported the synthesis of poly(ethylene oxide) (PEO) supported dendritic f-BOC-poly(a, c-L-lysines). These dendritic polymers termed as hydramphiphiles formed foams possessing good temporal stability in aqueous solution. Scrimin et al. [132] synthesized a three-directional polypeptide having uses in membrane permeability modulation. Decapeptide fragments were linked to TREN [tris(2-aminoethyl)amine] core. 

Employing 0.2 equiv. of polymer-bound dendritic Ti-TADDOLates of type 89 (1st and 2nd generation) enantioselectivities up to 98 2 were observed (Fig. 31). This value is comparable to those obtained in heterogeneous reactions using non-dendritic, polymer-bound analogs 88 (er up to 98,5 1,5 [ 105 ]) and with the... 

A comparison of the rates showed that the polymer-bound Ti-TADDOLate 88 and the dendritic polymer 89 catalyze the Et2Zn-to-PhCHO addition at a similar fast rate as the monomeric TADDOLate 86 and the dendritic TADDOLate 87 in homogeneous solution [107,112]. Further experiments also with other ligands are being carried out in our laboratories. 

Because reductive cleavage of aliphatic nitro compounds with Bu3SnH proceeds via alkyl radicals, nitro compounds are also used as precursors to alkyl radicals. Reactions using nitro compounds may have some advantages over other ones, since aliphatic nitro compounds are available from various sources. For example, the sequence of the Michael additions of nitro compounds provides an excellent method for the construction of quaternary carbon compounds (Eq. 7.79).126 Newkome has used this strategy for the construction of dendritic polymers (Eq. 7.80).127... 

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