Alexander Hymes

Chemistry and Biochemistry

Faculty Advisor: Haifeng Gao

Introducing exchangeable dynamic cross-links into polymer networks

Polymeric materials have infiltrated into every corner of our life from household items to industrial materials. Among these various applications, polymer thermosets with permanent crosslinks are often the choice of materials because of their dimensional stability, mechanical properties and creep/chemical resistance. However, these thermosets cannot be reshaped, processed or recycled. Considering the explosive growth of plastics waste resulting from difficulties in addressing end-of-life usage, there is a pressing need for a new generation of thermosets materials that can be reprocessed, like thermoplastics, yet still retain the beneficial properties of a crosslinked thermoset material. Recently, an attractive chemical strategy by introducing exchangeable dynamic cross-links into polymer networks is proposed. If chemical cross-links can be efficiently and reliably exchanged between different positions of the polymer chains, macroscopic flow can be achieved without risking structural damage or permanent loss of material properties. These polymer networks containing such exchangeable bonds are called as covalent adaptable networks or CANs. In this project, Alexander Hymes will be designing a type of CAN materials based on our recently developed Friedel-Crafts (F-C) hydroxyalkylation polymerization technique. Alex will be responsible for studying the imines exchange reaction in our F-C polymers to construct the CAN materials. By investigating the imine bond exchange kinetics under various conditions, Alex aims to identify the optimal materials composition and structure to produce CAN materials with the best mechanical properties and re-processibility.