PEP Review 94-1-4
Dendrimer Polymer from Diaminobutane and Acrylonitrile
The new dendrimer polymers have molecules that, unlike those of other polymers, are usually spherical as they approach their limiting size. In theory, all dendrimer molecules are the same size, although in practice they may deviate somewhat from this ideal; nonetheless, they still "have a well defined size" (560308) compared with normal polymers. Their unique uniformity and structure make dendrimers suitable for a variety of high technology uses, including medical imaging, site-specific drug delivery systems, and property/enhancing additives for polymers, paints and lubricants.
Of the many companies and universities researching dendrimer surfaces and internal structures, only Dendritech and DSM have announced production facilities. This review focuses on the DSM batch process, which is based on the addition of four molecules of acrylonitrile to diaminobutane, followed by hydrogenation that converts each nitrile to an amine group. Because two nitrile groups add to each amine group, each addition has two times as many nitrile groups as the previous addition. Alternating hydrogenation and addition reactions are carried out, adding layers until a spherical dendrimer of 6910 molecular weight is formed with an outer surface composed of 64 nitrile groups. To produce this precise structure, careful control is necessary to ensure that every reactive site is completely reacted during each addition and each hydrogenation, and that no side reactions take place. Intermediate products or the product of one additional hydrogenation (MW = 7166) can also be made with this process but are not examined extensively in this review.