Strategies for degradable dendrimers: Fragmenting o-nitrobenzyl ether dendrimers and disassembling oligomers of model dendritic systems

Two dendrimer cores that contain o-nitrobenzyl photolabile moieties have been synthesized from piperonal. Methylated core analogs undergo clean photocleavage as indicated by the evolution of isosbestic points in the UV spectra during photolysis and the observation of degradation products by ¹H NMR. These dendrimer cores serve as precursors to dendrimer-based photodegradable materials. Second generation benzyl aryl ether dendrimers have been synthesized and undergo clean photocleavage as indicated by the evolution of isosbestic points in the UV spectra during photolysis and the observation of degradation products by ¹H NMR. Two oligomeric models of disassembling dendrimers have been synthesized from vanillin and o-vanillin. The first system tests the para cleavage vector while the latter test cleavage through the ortho vector of dendrimer disassembly. These systems are used to test potential trigger groups prior to dendrimer synthesis due to their ease of synthesis. Each system shows clean cleavage when triggered by an allyloxy or o-nitrobenzyloxy trigger group as indicated by the evolution of isosbestic points in the UV spectra during disassembly and the observation of disassembly products by ¹H NMR. Dendrimers with a 2,4-branching motif have been synthesized. These dendritic systems have been triggered with and allyloxy group and undergo disassembly via both the ortho and para cleavage vectors simultaneously. Cleavage was noted by the evolution of an isosbestic point in the UV spectra during disassembly