Iterative Exponential Growth Synthesis and Assembly of Uniform Diblock Copolymers

Abstract

Studies on the phase segregation of unimolecular block copolymers (BCPs) are limited by a lack of reliable, versatile methods for the synthesis of such polymers on the preparative scale. Herein, we describe an advancement of Iterative Exponential Growth (IEG) wherein chiral allyl-based IEG oligomers are subjected to thiol-ene reactions and converted into unimolecular BCPs. With this strategy we have synthesized uniform BCPs with molar masses up to 12.1 kDa on ∼1 g scale. BCPs composed of decane-based side chains and either triethyleneglycol- or thioglycerol-based side chains phase-segregate into hexagonal cylinder morphologies. The assembly is not driven by side-chain crystallization, but is instead the result of amorphous BCP assembly.

Coding and decoding libraries of sequence-defined functional copolymers synthesized via photoligation

“…Further, bulk reactions have been conducted in flow systems based on iterative synthesis33. In addition, iterative exponential growth can lead to sequence-defined macromolecules343536. In parallel, strategies involving the consecutive insertion of single monomer units (vinyl or acrylate) based on radical processes started to emerge for the synthesis of sequence-defined polymers3738.…”

“…Concomitant to the development of new synthetic approaches to sequence-defined polymers, selected applications of such molecules are emerging, for example, bio-inspired structures for which high sequence definition is essential4546. For potential data storage applications, solid support-based systems have emerged featuring monomer units with unreactive variable alkyl groups47 and block copolymer phase separation based on sequence-defined oligomers has been demonstrated as well36. The herein proposed synthetic strategy based on photoreactive synthons offers significant applications of the functional sequence-defined macromolecules ranging from mild bioconjugation to base materials for advanced precision photoresists for, for example, direct laser writing48 or precision network formation for nuclear magnetic resonance (NMR) orientation media4950.…”

Stereochemical Sequence Dictates Unimolecular Diblock Copolymer Assembly

“…Our previous route to GPE from commercially available (R)- or (S)-epichlorohydrin (>99.5% ee) 9b, 10, 12 (Scheme 1C, Method A) provided GPE-A in 82% ee in our hands (Figure S19). In this work, (R)- or (S)-epichlorohydrin was treated with propargyl alcohol under Lewis acidic conditions to afford secondary alcohol S1 (see Figure S1), which was then exposed to sodium hydroxide, affording GPE-B in > 99% ee in 71% – 74% yield on ca.…”

“…Our syntheses of DPTs via IEG 10 rely upon copper-catalyzed azide-alkyne cycloaddition (CuAAC) reactions 11 to construct the DPT backbone and thiol-ene addition reactions to install sidechain functionalities. Monomers bearing either an azide or a terminal alkyne are derived from glycidal propargyl ether (GPE) in a divergent fashion (Scheme 1A).…”

Recent Progress in the Design of Monodisperse, Sequence-Defined Macromolecules

“…However, the targeted introduction of tailored side chains in every repeat unit is challenging in IEG‐approaches. Thus, the synthesis is limited to repetitive or palindromic sequences, which can, however, be synthesized in fewer steps than in conventional iterative step by step approaches . Interestingly, iterative exponential growth strategies are named divergent/convergent approaches in the field of conjugated, monodisperse macromolecules (compare Section ).…”