Synthesis of poly(N-isopropylacrylamide) by ATRP using a fluorescein-based initiator

A new fluorescent initiator fluorescein 2-bromoisobutyrate (Flu- Br) was synthesized. The use of Flu- Br as initiator, Me6TREN as ligand and CuCl as catalyst by atom transfer radical polymerization allowed for chain-end fluoresceined poly(N-isopropylacrylamide) ( Flu-PNIPAM) in one step. The polymerization reached high conversion ( 65 %) and low polydispersity (PDI) (1.15-1.28). The linearity plot of the Mn, GPC and Mn, NMR against conversion and the low PDI revealed the well-controlled polymerization by ATRP. In addition, N-isopropylacrylamide (NIPAM) was copolymerized with hydrophilic N, N-dimethylacrylamide (DMAM) using Flu- Br initiator by ATRP. By changing the feed ratio of NIPAM to DMAM, it was very easy to obtain thermo-sensitive fluorescent copolymers with proper lower critical solution temperature (36.0 +/- 0.2 degrees C, 38.0 +/- 0.2 degrees C). The pH dependence on fluorescence intensity of Flu- PNIPAM displayed a similar behavior to the parent fluorescein.