(595c) Combining Polymer Synthesis with Self-Assembly of Block Copolymers

Authors: 
Qiang, Z., Northwestern University
Wang, M., Northwestern University
Self-assembly of polymers has emerged as an important and promising technique for nanopatterning due to its advantages of low cost and high versatility. The conventional strategy requires two separate steps including (1) chemical synthesis and (2) physical assembly, where the resulting morphology is governed by the underlying polymer chemistry. Altering the nanostructures of block copolymer (BCP) films from its thermodynamic equilibrium state is challenging, due to our very limited control over chemistry during or after self-assembly. Integrating polymer synthesis within a self-assembled film would enable exact on-demand control over the resulting morphology, functionality, and properties in different regions.

In this talk, we will demonstrate a new approach for performing polymerization reactions within block copolymer thin films. The vapor phase monomer is first introduced into the block copolymer film, which can be subsequently converted to polymers through the photopolymerization. The newly synthesized homopolymers blend with BCP films and alter the nanostructures by changing the underlying polymer chemistry and composition. Identical photopolymerization conditions with lower UV intensity causes more expansion of selective domains due to the addition of higher molecular weight homopolymers, leading to highly asymmetric nanopatterns. As these altered nanostructures are locally near equilibrium, this method can be adapted and combined with common annealing techniques to improve order. This strategy also enables a stable phase of toroidal micelles by polymerizing a monomer that has distinct chemistry compared to the block copolymer chemical composition. By successfully combining polymer chemistry with self-assembly, this in-film polymerization method provides an exciting platform for on-demand synthesis as well as opening up a new area for radical polymerizations of monomers within geometrically confined, swollen films.