Synthesis and Characterization of Model Dumbbell Polymers

High molecular weight dumbbell shaped polymers were prepared by atom transfer radical polymerization (ATRP) to grow branches from repeat units of end blocks of a symmetric triblock copolymer. The triblock copolymer itself was prepared by polymer−polymer coupling of a commercially obtained α,ω-end functionalized polystyrene as central block with end-functionalized poly(chloromethylstyrene) that we synthesized by nitroxide-mediated polymerization. Temperature gradient interaction chromatography (TGIC) enabled the estimation of the terminal hydroxyl functionality of the high molecular weight α,ω-difunctional polystyrene as 75%. Size exclusion chromatography (SEC) and 1H NMR enabled the determination of molecular weights and verification of the structures of the intermediate and the cleaved products. Size exclusion chromatography coupled with light scattering (SEC-LS) and scanning force microscopy (SFM) were used to confirm that the desired dumbbell architecture was obtained.