Covalent Adaptable Networks with Tailorable Material Properties Based on Divanillin Polyimines

TL;DR

This paper introduces covalent adaptable networks made from renewable materials that can be reprocessed and recycled while maintaining strong mechanical properties.

Contribution

The study presents a new class of sustainable covalent adaptable networks with tailorable properties and chemical recyclability.

Findings

CANs showed tensile strength ranging from 1.07 to 18.7 MPa and glass transition temperatures from 16 to 61 °C.

The materials were reprocessed up to three times without structural changes and retained mechanical performance.

Divanillin monomer was successfully recovered and reused for synthesizing recycled CANs with similar properties.

Abstract

Covalent adaptable networks (CANs) are being developed
as future
replacements for thermosets as they can retain the high mechanical
and chemical robustness inherent to thermosets but also integrate
the possibility of reprocessing after material use. Here, covalent
adaptable polyimine-based networks were designed with methoxy and
allyloxy-substituted divanillin as a core component together with
long flexible aliphatic fatty acid-based amines and a short rigid
chain triamine, yielding CANs with a high renewable content. The designed
series of CANs with reversible imine functionality allowed for fast
stress relaxation and tailorability of the thermomechanical properties,
as a result of the ratio between long flexible and short rigid amines,
with tensile strength (σb) ranging 1.07–18.7
MPa and glass transition temperatures ranging 16–61 °C.
The CANs were subsequently successfully reprocessed up to three times
without determinantal structure alterations and retained mechanical
performance. The CANs were also successfully chemically recycled under
acidic conditions, where the starting divanillin monomer was recovered
and utilized for the synthesis of a recycled CAN with similar thermal
and mechanical properties. This promising class of thermosets bearing
sustainable dynamic functionalities opens a window of opportunity
for the progressive replacement of fossil-based thermosets.

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