Dendritic-Linear Hybrid Multiarm Star Polymers: A Straightforward Synthesis of Polymer as Molecular Nanoparticles

Synthesis of multiarm star polymers via "core first" method but possibly through two different chain growth fashions has been described. Two distinct styrenyl-TEMPO-based G3 and G4 dendritic unimolecular initiators have been used for this method. Polymerization of styrene using these core-cum-initiators at 125 degrees C varying the monomer to initiator ratio and polymerization time yields multiarm star polymers with molecular weight (M-w) in the range of 1.71 x 10(5) to 4.75 x 10(5) g mol(-1) and polydispersity in the range of 1.34-1.46. Hydrolysis leading to degradation of inner polyurethane core yields highly narrow dispersed-PDI 1.00 to 1.04-polystyrene chains, and the SEC-MALLS data of these chains confirm the accurate control on predetermination in the number of arms up to 48 of star polymers. The specific refractive index increment (dn/dc) of the polymers is found to be decreased with decreasing weight fraction of core. The transmission electron microscope (TEM) and atomic force microscopy (AFM) images and hydrodynamic radius of chosen polymers confirm the two different chain growth fashions leading to the formation of star polymers as discrete nanoparticle in the case of initiator in which TEMPO is anchored and formation of peripherally low entangled short chains in the case of initiators in which TEMPO is end-capped.