Novel Nanoscopic Architectures. Linear-Globular ABA Copolymers with Polyether Dendrimers as A Blocks and Polystyrene as B Block

The synthesis of novel linear-dendritic triblock copolymers was achieved via anionic polymerization of styrene (St) initiated by potassium naphthylide, subsequent modification of the “living” poly-St with 1,1-diphenylethylene, and final quenching with reactive dendrimers. The effectiveness of the coupling was high as confirmed by size-exclusion chromatography (SEC) with photodiode array detection. The ABA block copolymers were characterized by SEC with coupled viscometry and multiangle laser light scattering, NMR, and thermal analysis. It was found that, in solution, these hybrid materials have radii of gyration between 2.5 and 15 nm. They undergo a shape transition from an extended globular form to a statistical coil as the molecular weight of their linear (poly-St) block increases. All ABA copolymers seem to experience substantial entanglements in the solid state, but they have a single T_g with values ranging from 313 to 367 K, indicating that the linear and dendritic blocks are miscible on the molecular level unlike physical mixtures of their two individual components.