Extended-core discotic liquid crystals based on the intramolecular H-bonding in N-acylated 2,2'-bipyridine-3,3'-diamine moieties

Electrospray mass spectrometry (ESI-MS) is used to analyze in detail the structure of the first five generations of the poly(propyleneimine) dendrimers with 4-64 end groups. Although the reaction sequence to prep. these dendrimers is highly optimized, an accumulation of statistical defects is obsd. at higher generations. A simple statistical simulation allows the assignment of all peaks in the deconvoluted spectrum and the detn. of yields for each side reaction in the formation of each generation. The fifth generation of the poly(propyleneimine) dendrimer contg. amine end groups, which is formed after 248 consecutive reaction steps, possesses a dendritic purity of approx. 20%, which corresponds to a polydispersity of approx. 1.002. The defects in the divergent growth patterns of dendrimers are compared to those obsd. in the Merrifield synthesis of polypeptides