Synthesis And Properties Of Fluorescent Functionalized Miktoarm Star Polymers

Reversible addition fragmentation chain transfer(RAFT)polymerization has the great advantages of wide range of monomers and easy mild reaction conditions.It is widely used in the preparation of functionalized polymers with complex topological structures with predicted molecular weight and narrow molecular weight distribution including block copolymers and star polymers,etc.Fluorescence dyes have great value in bio-imaging,fluorescence probes and many other fields.In this research,seven kinds of fluorescent functionalized RAFT agents,such as dansyl chloride,rhodamine B,anthracene,coumarin,BODIPY and bisindolylmaleimide,have been designed and synthesized via different synthetic routes.The structures and purities of all intermediates and final products were determined by nuclear magnetic resonance and mass spectrometry.Subsequently,we prepared a series of fluorescent end-capped linear polymers with the fluorescence labeled RAFT reagents,which proved that the fluorescence groups modified RAFT agents still possess great controllability over polymerization and chain extension process.Moreover,the results showed that the fluorescence end group had considerable residual amounts in all polymer samples.During the investigation of fluorescence properties,we found that fluorescence-labeled polymers' emission intensity increased linearly with concentration over a range of concentrations which was normally regarded as the nature of small molecular dyes.Standard curves of the polymer fluorescence were obtained afterwards with high linear fitting constants.This findings can be used in calculating the molecular weight or the concentration of unknown fluorescence labeled polymers.Finally,a series of miktoarm star polymers were synthesized by changing the feed ratio of different arms via RAFT mediated "arm first" approach.The average arm contents were analyzed by the fluorescence properties which provided a novel pathway for the characterization of star polymers prepared by "arm first" approach.