Polymer chemists have long tried to replicate Nature’s remarkable ability to make macromolecules of defined length, sequence, and chirality. Many new synthetic approaches have attempted to access precisely defined and diversely functionalized uniform macromolecules in useful quantities. We are advancing a promising alternative synthetic strategy called Iterative Exponential Growth (IEG) wherein doubly protected molecules of length L undergo cycles of orthogonal activations and couplings to yield macromolecules with length L x (2^n) cycles. Though IEG is limited to repetitive or palindromic sequences, we have used it to make unimolecular, fully sequence-controlled and stereocontrolled polymers on multigram scales. Through synthetic modification of our base monomers, we can install a variety of functionalities such as alcohols, electron donating and accepting aromatics, free amines, and primary alkenes. We have only just started exploring the vast sequences and topologies that can be made using our system. For instance, using sequential thiol-ene click chemistry, we have synthesized unimolecular block copolymers (BCPs) of up to 12.1 kDA on a gram scale in under a week. BCPs of decane-based side chains and either triethyleneglycol- or thioglycerol-based side chains phase-segregate into hexagonal cylinder morphologies. It is our hope that by using our IEG system, we will elucidate the structure−property relationships that will guide the design of next-generation polymeric materials.

Iterative exponential growth of stereo- and sequence-controlled polymers

256th National Meeting (2018)

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