Synthesis of double side-chain liquid crystalline block copolymers using RAFT polymerization and the orientational cooperative effect

We report on the synthesis and characterization of a new type of diblock copolymer that is composed of two side-chain liquid crystalline polymers (SCLCP1-block-SCLCP2). The diblock copolymer of poly{6-[4(4-methoxyphenylazo)phenoxy]hexyl methacrylate}-block-poly{6-[4-(4-cyanophenyl)phenoxy]hexyl methacrylate} (PAzoMA-b-PBiPMA) was successfully synthesized using the reversible addition-fragmentation chain transfer (RAFT) polymerization. Low-polydispersity samples of various compositions can be prepared using either PAzoMA or PBiPMA macromolecular chain transfer agent. We show that the orientational cooperative effect can be effective even in microphase-separated samples due to the interaction of the two mesogens via the interface. Indeed, the photoinduced orientation of azobenzene groups on the PAzoMA block can bring biphenyl groups on the PBiPMA block to orient in the same direction inside their respective lamellar domains. While RAFT can be used to access to double or all-SCLC block copolymers, this study also demonstrates the potential interest of exploring the interplay of the LC order of different SCLCPs within a microphase-separated system.