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 siloxane–poly(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.