# Efficient Synthesis of Chemically Recyclable Polyamides via Substituent Effects‐Enabled Mechanistic Pathway

## TL;DR

A new method for making polyamides uses a chemical called DADC, which allows for lower temperature synthesis and chemical recycling of the resulting polymers.

## Contribution

The study introduces a catalyst-free, low-temperature method for polyamide synthesis using DADC's substituent effects.

## Key findings

- DADC reacts with amines at 80-120°C without catalysts, much lower than traditional methods.
- The DADC-synthesized polyamides are thermally reprocessable and chemically recyclable under mild conditions.
- The reactivity of DADC is due to synergistic substituent effects from its ketone and diester groups.

## Abstract

Imination and amidation are two fundamental condensation reactions central to modern chemical synthesis, and devising energy‐efficient ways to trigger them is highly relevant in advancing low‐carbon manufacturing, with most approaches relying on the use of catalysts. Here, we revisit the dimethyl acetone‐1,3‐dicarboxylate (DADC) chemistry, and show that it can react with a broad range of small‐molecule and macromolecular amines at moderate temperatures (80‒120 °C) in the absence of any catalysts. This represents a significant reduction in processing temperatures compared to traditional polycondensation methods for polyamide synthesis, which often require temperatures exceeding 230 °C. Mechanistic and model studies reveal that the high reactivity of DADC toward amines arises from its synergistic substituent effects; Specifically, the two ester groups in the symmetric β‐position of DADC’s ketone facilitate initial imination via conjugation and electron‐withdrawing effects, generating a β‐enamino intermediate. This β‐enamine subsequently engages in intramolecular hydrogen bonding with one ester group, reducing steric hindrance on the remaining ester and thus promoting its amidation. Moreover, we demonstrate that the DADC‐synthesized polyamides are thermally reprocessable, and chemically recyclable under either acidic or basic conditions at mild temperatures, and the chemical recycling is possible both for the neat polymer and its mixture with other plastics.

The joint presence of ketone and diester functionalities in dimethyl acetone‐1,3‐dicarboxylate enhances its reactivity toward amines compared to the individual reactivity of each group, due to substituent effects. This increased reactivity enables the efficient synthesis of polyamides under mild conditions, and the resulting polymers are chemically recyclable.