Multi-armed, TEMPO-functionalized unimolecular initiators for starburst dendrimer synthesis via stable free radical polymerisation. 2. Tris (1,3,5)benzyloxy unimers

The synthesis of the trifunctionalized TEMPO-modified unimolecular initiators, unimers I, II, and III is described. Unimer I was prepared via an S(N)2 type Williamson ether coupling of 1,3,5-tris(iodomethyl)benzene with a TEMPO-containing ethylbenzene hydroxy derivative. The synthesis of unimer II, however, was accomplished through S(N)1 reaction of 1,3,5-tris(bromomethyl)benzene with the hydroxy-ethylbenzene TEMPO derivative in the presence of silver triflate. Synthesis of unimer III started from phloroglucinol and an SNAr reaction with 1-fluoro-4-nitrobenzene, followed by reduction to the amino compound and Schiff base formation with the TEMPO-derivatized aromatic aldehyde. Stable free radical polymerisation (SFRP) of styrene and acetoxystyrene with unimer I are also described with molecular weights and polydispersities reported. It is concluded that the SFRP of styrene with a triradical initiator meets the requirements of a living system.