Dendrigraft architecture

Figure 1.10 Comparison of dendrimer and dendrigraft architecture Generation 0-2...

Figure 30.2 Molecular weight dependence of intrinsic viscosity [/ ] for polymers with (a) linear, (b) hyperbranched, (c) dendrimer, and (d) dendrigraft architectures. Source Reproduced with permission from Tomalia DA, Frechet JMJ. Introduction to the dendritic state. In Tomalia DA, Frdchet JMJ, editors. Dendrimers and Other Dendritic Polymers. West Sussex Wiley 2001. p 3 [14]. Copyright 2001 John Wiley and Sons.

Very recent work in the Tomalia-Baker group [174] has shown that certain classes of dendritic architecture offer distinct advantages as scaffolding for presenting C-sialoside groups. For example, use of dendrigraft architecture [175] as... 

Figure 1.23 Intermediary of (III) branched and (IV) dendritic architecture in the conversion of (I) linear thermoplastics to (II) crosslinked thermoset polymers. Intermediary of (IVb) dendrigrafts and (IVc) dendrimers in the formation of megamers...

Dendritic polymers, the fourth major architectural class of macromolecules, can be divided into three subclasses. These subclasses may be visualized according to the degree of structural perfection attained, namely (1) hyperbranched polymers (statistical structures, Chapter 7), (2) dendrigraft polymers (semi-controlled structures, reviewed in this chapter) and (3) dendrimers (controlled structures, Chapter 1). 

The synthetic approach used for dendrigraft-po y(butadicncs) has the potential to provide control over the composition and architecture of the molecules. The branch molecular weight is easily varied with the amount of initiator used in the polymerization reaction. Solvent polarity control in the polymerization allows variation of the proportion of 1,2-units in the side chains, and hence the branching density. 

Some 17 years later, many of these predictions are turning into experimental reality as many of these questions are being answered in each new publication or patent that appears on dendritic architecture. Presently, dendritic polymers are recognized as the fourth major class of polymeric architecture consisting of three subsets that are based on degree of structural control, namely (a) random hyperbranched polymers, (b) dendrigraft polymers and (c) dendrimers (Figure 6). 

In the beginning, the term dendrimer , which was established by Tomalia in 1985 [42,43], described all types of dendritic polymers. Later a distinction based on the relative degree of structural control present in the architecture was drawn. Nowadays, many other types of dendritic architectures are known, even if most of them, however, have not yet been widely investigated and fully characterized. The term dendritic polymer involves four substructures (Fig. 2), namely dendrimers themselves, dendrons, random hyperbranched polymers, and dendrigraft polymers [44, 45],... 

More recently, nontraditional polymerization strategies have evolved to produce a fourth new major polymer architectural class, now referred to as dendritic polymers. This new architectural polymer class consists of four major subsets, namely (a) random hyperbranched, (b) dendrigrafts, (c) dendrons, and (d) dendrimers. Dendrimers, the most extensively studied subset, were discovered by the Tomalia group while at The Dow Chemical Company laboratories (1979). They represent the first example of synthetic, macro-molecular dendritic architecture [33,34]. First use of the term dendrimer appeared in preprints for the 1st SPSJ International Polymer Conference held in Kyoto, Japan (1984). The following year, a full article Polymer Journal, Vol. 17, No. 1, pp. 117-132 (1985)) (see article abstract. Fig. 42.7) described the first preparation of a complete family of... 

Frechet [43,106] was the first to compare viscosity parameters for (A) linear topologies, as well as (B) random hyperbranched polymers and (C) dendrimers. More recently, we reported such parameters for (D) dendrigraft polymers [105] as shown in Fig. 42.15. It is clear that all three dendritic topologies behave differently than the linear architecture. There is, however, a continuum of behavior wherein, random hyperbranched polymers behave most nearly like the linear systems. Dendrigrafts exhibit intermediary behavior whereas, dendrimers show a completely different relationship as a function of molecular weight. 

Dendritic architectures are highly branched polymers with tree like branching having an overall spherical or ellipsoidal shape and are known as additives having peripheral functional groups. These macromolecules consist of three subsets namely dendrimers, dendrigraft polymers and hyperbranched polymers (Figrrre 1). 

Properties Dendritic architectures Dendrimers Dendrigraft Hyperb ranched... 

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