Unexpected Strong Blue Photoluminescence Produced from the Aggregation of Unconventional Chromophores in Novel Siloxane-Poly(amidoamine) Dendrimers

Poly(amidoamine) (PAMAM) dendrimers and hyperbranched poly(amidoamine)s are the first reported and most investigated luminescent polymers containing unconventional chromophores. The luminescence of these compounds is associated with the N-branched tertiary amine moiety, and the oxidation of the tertiary amine is assigned to the emitting source. However, in this paper, a series of novel siloxanepoly(amidoamine) (Si-PAMAM) dendrimers were synthesized by aza-Micheal reaction, and strong blue photoluminescence was observed even with the naked eye when these compounds were excited by a UV lamp. All of these compounds were not oxidated at all. Studies on the molecular structure showed that N -> Si coordination bonds existed in these compounds, and those N -> Si bonds caused the aggregation of carbonyl groups which show the strong luminescence.