Phenylacetylene-based dendrimers

Similarly, phenylacetylene based dendrimers [7, 8] and those investigated by Goodson and co-workers [15] show substantial coupling between the branches while all others discussed above, due to flexibility of the connecting arms, have an undefined three-dimensional structure and hence variable donor-acceptor distances. 

The chemistry used to prepare phenylacetylene dendrimers is also based on this methodology in view of the multiple conversions, a high-yielding and well-established procedure was required. The dendrimer was prepared in an elegant way by repeating the cross-coupling and deprotection using monomers such as those shown in Scheme 5-5 [58]. 

Liquid crystalline dendrimers characterized by a well-defined molecular weight and exhibiting thermotropic columnar mesophases have been reported very recently. An example is the dendrimers based on the stiff, triconnected phenylacetylene monomer [93] is shown in Fig. 18. 

Hyperbranched Macromolecules. Because of their close structural and synthetic similarities to dendrimers, the comparison of hyperbranched macromolecules with their dendritic analogs has been studied by a number of groups. Ihre and Hult(7i) have recently reported the synthesis and characterization of the dendritic analogs of the commercially available hyperbranched polyesters, Boltron(D(7, based on 2,2-bis(hydroxymethyl)propionic acid, while Moor iJ) has reported a novel solid-supported synthesis of hyperbranched poly(phenylacetylenes) which are the hyperbranched analogs of Moore s well studied phaiylacetylene dendrimers(id). An intriguing study was also reported by Feast into the synthesis and physical properties of hyperbranched analogues of Tomalia s poly(amidoamine) dendrimers (77). 

Irrespective of these differences, both approaches have proved to be extremely successful for the preparation of dendritic macromolecules. By the use of either the divergent or convergent growth approaches a number of different groups have prepared dendrimers based on a wide variety of functional groups i.e. dendritic poly(amides) (5), poly(etherketones) (6), poly(amines) (7), poly(phenylenes) (8), poly(silanes) (9), poly(phosphonium salts) (10), poly(esters) (11), poly(phenylacetylenes) (12), poly(alkanes) (13), etc. Interesting variations on this theme have been the preparation of optically active dendrimers (14), dendritic poly(radicals) (15), and dendrimers based on co-ordination chemistry with... 

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