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Date Permissions Signed


Date of Award

Fall 2020

Document Type

Masters Thesis

Department or Program Affiliation


Degree Name

Master of Science (MS)



First Advisor

Larsen, Michael B.

Second Advisor

O'Neil, Gregory (Gregory W.)

Third Advisor

Murphy, Amanda R.


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.




carbodiimide, guanidine, metathesis, covalent adaptable network, recycable, novel polymer, postpolymerization modification, poly2-aminooimidazole


Western Washington University

OCLC Number


Subject – LCSH

Carbodiimides; Plastics--Recycling; Plastics--Environmental aspects; Thermoplastics--Recycling; Thermoplastics--Environmental aspects; Polymers--Analysis




masters theses




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