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Optical Alignment of Si-Containing Nanodomains Formed by Photoresponsive Amorphous Block Copolymer Thin Films

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journal contribution
posted on 03.01.2020, 19:03 by Mitica Cezar Spiridon, Nils Demazy, Cyril Brochon, Eric Cloutet, Georges Hadziioannou, Karim Aissou, Guillaume Fleury
A series of amorphous block copolymers (BCPs), consisting of a low-glass-transition polydimethylsiloxane (PDMS) block associated with a photoresponsive azobenzene-containing poly­(disperse red 1 methacrylate-co-alkyl methacrylate) (P­(DR1MA-co-RMA)) block, were prepared from a PDMS macro-chain transfer agent used for the reversible addition–fragmentation chain-transfer (RAFT) copolymerization of binary mixtures of methacrylate monomers of various compositions. The resulting BCPs containing up to 40 wt % of azo dye exhibited low dispersity demonstrating a good control of the RAFT polymerization through the copolymerization of the DR1MA and RMA units. Long-range-ordered in-plane PDMS cylinders were produced by exposing the (as-cast) disordered BCP thin films to a p-polarized laser beam, to orthogonally align the azo groups with the polarization direction, prior to promoting the microphase separation of the BCP domains with a solvent vapor annealing treatment. Conversely, the photoinduced alignment of the azo chromophores was not effective within microphase-separated BCP thin films since randomly oriented PDMS features were observed after exposure to a p-polarized laser light.

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