We report the synthesis and design of a Y-shaped inimer (polymerizable initiator) that contains two different initiators attached at a single junction point. The Y-inimer contains an initiator for atom transfer radical polymerization (ATRP) and an initiator for nitroxide-mediated polymerization (NMP) along with a polymerizable methacrylate group. While Y-shaped initiators have been reported in the literature, a polymerizable version has not been demonstrated. Synthesis of the Y-shaped inimer is based on a one-pot multi-component reaction of a benign formamide monomer. We further demonstrate the versatility of this inimer by homopolymerization and copolymerization with crosslinkable monomers. The synthesis of bottlebrush copolymers with precise 1:1 ratio of A and B chains is demonstrated. Crosslinkable versions of the inimer copolymer were synthesized and coated on to a silicon substrate for growth of A/B mixed polymer brushes with high grafting density and uniform grafting ratios. Bottlebrush copolymers that contain two different side chains (A and B) exhibit a wide range of morphologies based on their compositions. They can be synthesized by copolymerization of different macromonomers (grafting-through) or by grafting different polymer chains onto the backbone by post-functionalization methods (grafting-to). However, attaining perfect 1:1 ratio between the A and B side chains remains a challenge since existing methods incorporate A and B polymer chains in separate processes that have different efficiencies. The Y-inimer has the potential to create both bottlebrush copolymers and mixed polymer brushes with increased grafting density due to multiple initiating sites on a single repeating unit. Both systems have great potential for self-assembly due to extraordinary high grafting density leading to an unexplored region of morphology.

Y-shaped inimer for the synthesis of mixed polymer brushes

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