Carbodiimides: Templates for Covalent Adaptable Networks and Post Polymerization Modification
Year: 2020
Type: article
Abstract: The global increase in plastic waste has negatively impacted the environment, human health, and economy. Plastics that lack recyclability, such as thermosets are some of the main culprits. To help address this issue, reactive functional groups can be incorporated in macromolecules, enabling straightforward post-polymerization modification (PPM) that can enhance their ability to be recycled. This thesis studied carbodiimides as a reactive functional group for facile PPM with amines through a catalyst-free transformation to N,Nʹ,Nʺ-trisubstituted guanidines. Small molecule studies showed that N,Nʹ,Nʺ-trisubstituted guanidines underwent a reversible thermal exchange reaction without a catalyst. The newly found thermal exchange reaction, termed thermal guanidine metathesis (TGM), was used as the basis for a new type of covalent adaptable network (CAN). At elevated temperatures the CAN transitioned from thermoset to thermoplastic-like rheological behavior, which allowed the material to be reprocessed. TGM-based CANs exhibited vitrimer-like behavior such as a relatively constant crosslink density and the Arrhenius scaling of relaxation times. Additionally, differences in activation energy determined by small molecule studies and stress relaxation analysis were consistent with the Semenov-Rubinstein model of thermoreversible highly crosslinked networks. This thesis also studied the transformation of carbodiimides with multifunctional amines for novel polymers using PPM.
Authors: Melchor Bañales, Julian E. Alberto
Language: English
Subfield: Polymers and Plastics
Field: Materials Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W3155955127