Polymerization-Induced Nanostructural Transitions Driven by In Situ Polymer Grafting.

Polymerization-induced structural transitions have gained attention recently due to the ease of creating and modifying nanostructured materials with controlled morphologies and length scales. Here, we show that order-order and disorder-order nanostructural transitions are possible using in situ polymer grafting from the diblock polymer, poly(styrene)--poly(butadiene). In our approach, we are able to control the resulting nanostructure (lamellar, hexagonally packed cylinders, and disordered spheres) by changing the initial block polymer/monomer ratio. The nanostructural transition occurs by a grafting from mechanism in which poly(styrene) chains are initiated from the poly(butadiene) block via the creation of an allylic radical, which increases the overall molecular weight and the poly(styrene) volume fraction. The work presented here highlights how the chemical process of converting standard linear diblock copolymers to grafted block polymers drives interesting and controllable polymerization-induced morphology transitions.