ß-Triketones as Reactive Handles for Polymer Diversification via Dynamic Catalyst-Free Diketoenamine Click Chemistry.

The spontaneous condensation of amines with ß-triketones (TK), forming ß,ß'-diketoenamines (DKE) and releasing water as the sole byproduct, exhibits many of the hallmarks of "click" reactions. Such characteristics render TKs as a highly advantageous platform for efficient polymer diversification, even in biological contexts. Leveraging reversible addition-fragmentation chain transfer (RAFT) and photoiniferter polymerization of novel TK-containing vinylic monomers, we synthesized polymers containing pendent TKs with excellent control of molecular weights, even in excess of 106 g mol-1. Under mild, catalyst-free conditions, poly(ß-triketone methacrylate) could be modified with a diverse scope of amines containing a plethora of functional groups. The high efficiency of this functionalization approach was further emphasized when grafting-to with poly(ethylene glycol)-amine resulting in bottlebrushes with molecular weights reaching 2.0 × 107 g mol-1. Critically, while the formed DKE linkages are stable under ambient conditions, they undergo catalyst-free, dynamic transamination at elevated temperatures, paving the way for associative covalent adaptable networks. Overall, we introduce pendent triketone moieties into methacrylate and acrylamide polymers, establishing a novel postpolymerization modification technique that facilitates catalyst-free ligation of amines under highly permissible conditions.

Diversification of Acrylamide Polymers via Direct Transamidation of Unactivated Tertiary Amides.

Postpolymerization modification offers a versatile strategy for synthesizing complex macromolecules, yet modifying acrylamide polymers like poly(N,N-dimethylacrylamide) (PDMA) is notoriously challenging due to the inherent stability and low reactivity of amide bonds. In this study, we unveil a novel approach for the direct transamidation of PDMA, leveraging recent advances in the transamidation of unactivated tertiary amide substrates. By exploiting photoiniferter polymerization, we extended this direct transamidation approach to ultrahigh-molecular-weight (UHMW) PDMA, showcasing the unprecedented postpolymerization modification of synthetic polymers exceeding 106 g/mol. We also designed acrylamide copolymers comprising both the moderately reactive N-methyl-N-phenyl tertiary amides, along with the less reactive, fully alkyl-substituted N,N-dimethyl amides inherent to PDMA. This disparate reactivity enabled a sequential, chemoselective transamidation by initially targeting the more reactive pendant aryl amides with less nucleophilic aromatic amines, and second, transamidating the untouched N,N-dimethyl amide moieties with more nucleophilic aliphatic amines, yielding a uniquely diversified acrylamide copolymer. This work not only broadens the scope of postpolymerization modification strategies by pioneering direct transamidation of unactivated amides but also provides a robust platform for the design of intricate macromolecules, particularly in the realm of UHMW polymers.