Approaches to phthalimido and amino end-functional polystyrene by atom transfer radical polymerisation (ATRP)

Approaches to the synthesis of amine end-functional polystyrenes through intermediary phthalimido end-functional polystyrenes have been explored. Phthalimido groups can be quantitatively converted to amine groups by hydrazinolysis according to an Ing--Manske procedure. Approaches based on alpha- (functional initiator) and omega-functionalisation (end-group substitution) were examined. Thus, well defined, low molecular weight, omega-bromopolystyrenes, prepared by atom transfer radical polymerisation (ATRP) with copper(l) bromide, 4,4'-di-(nonyl)-2,2' bipyridine (dNbpy) and 1-bromoethylbenzene initiator, were transformed into omega-phthalimidopolystyrenes by substitution with potassium phthalimide. However, elimination of the terminal bromine to form an unsaturated chain end was observed as a side reaction. Various alpha-phthalimidopolystyrenes were successfully prepared using plithalimido-functional initiators. Phthalimido-functional bromo isobutyrate derivatives proved very effective in yielding very low polydispersity polystyrene (M-w/M-n similar to 1. 1). However, the conversion of the derived alpha-phthaliniidopolystyrense to an alpha-aminopolystyrene was problematic because of concomitant hydrazinolysis of the isobutyrate ester linkage and other side reactions. N-(Bromomethyl)phthalimide was successfully used as an ATRP initiator to prepare low polydispersity alpha-pthalimidopolystyrene (M-w - M-n similar to 1.3) and thence alpha-aminopolystyrene with a high degree of end-group purity. End-group interconversions were followed by H-1 NMR. (c) 2005 Elsevier B.V. All rights reserved.