Arborescent polymers

Mario Gauthier (University of Waterloo) for the PS Arborescent polymers. Special thanks to the NIST dendrimer team who provided all of the characterization work, Andreas Topp, Ty J. Prosa, Da-Wei Liu, Catheryn L. Jackson, and Giovanni Nisato. This work is supported in part by the US Army Research Office under contract number 35109-CH. 

In spite of this difficult acceptance, it is quite remarkable to note that by the end of 1990 about two dozen publications on dendrimers had appeared in refereed journals. By the end of 1991 the rate of publication of dendrimer papers had started to climb markedly while there still were only three papers on random hyperbranched polymers and two on dendrigraft or arborescent polymers. The courage, persistence and credibility of many key scientists listed in Table 1 during that period, set the stage for the explosive acceptance and recognition of dendritic polymers over the next decade. 

Arborescent Polymers The first grafting technique developed for the synthesis of arborescent polymers used chloromethyl coupling sites located on the phenyl pendants of PS substrates. Coupling living polystyryl anions... 

Another embodiment of this technique was used for the synthesis of high molecular weight, low B arborescent polymers by Yuan and Gauthier in a one-pot synthesis of arborescent PSs [114]. In this case, the anionic copolymerization of styrene (Sty) and 1,3-diisopropenylbenzene (DIB) initiated by iec-butyllithium was carried out in a semibatch process. Following complete monomer conversion, the chains were terminated and the isopropenyl moieties of the DIB units were activated with xec-butyllithium to produce a polyfunctional anionic macroinitiator without additional workup. Further styrene-DIB monomer mixture additions yielded a comb-branched (GO) copolymer, and... 

This chapter focuses on the latest efforts in our laboratory aimed at the synthesis and the physical characterization of arborescent polymers. The synthesis of arborescent styrene and isoprene homopolymers is discussed, together with copolymers incorporating a polystyrene substrate grafted with side chains of different compositions such as poly(2-vinylpyridine). 

Scheme 6.1 General scheme for the synthesis of arborescent polymers. (Reprinted from Progress in Polymer Science, 29, S. J. Teertstra and M. Gauthier, Dendrigraft polymers Macromolecular engineering on a mesoscopic scale, 277-327, 2004, with permission from Elsevier.)...

The step-wise synthesis of arborescent polymers, while able to generate large amounts of materials in good yield, requires isolation and purification of the crude product prior to substrate functionalization. For less-demanding applications not requiring stringent removal of the linear polymer contaminant, a one-pot method was recently developed by Yuan and Gauthier (2006) for the synthesis of arborescent polystyrene without isolation of the reaction intermediates. 

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