Abstract
Inclusion of dynamic covalent chemistries within polymer networks has been a topic of significant research due to the ability to endow these materials with reprocessability and recyclability; however, cleavage of dynamic bonds could also serve as a toughening mechanism in glassy thermosets. The influence on mechanical properties of including dynamic disulfide bonds within thermoset epoxies is investigated across broad temperatures and by utilizing several techniques including dynamic mechanical analysis, uniaxial tension and compression, microindentation, and fracture toughness testing. By analyzing the results in the context of a cohesive zone model, it was determined that the observed improvement in toughness in the disulfide-containing epoxies likely results from increased extensibility in the process zone due to preferential cleavage of disulfide linkages before macroscopic network failure. Observation of mechanochromic thiyl radicals in compression samples also provides evidence for increased plasticity in these dynamic glasses and suggests high strains are required for mechanical activation.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 2583-2595 |
| Number of pages | 13 |
| Journal | ACS Applied Polymer Materials |
| Volume | 5 |
| Issue number | 4 |
| DOIs | |
| State | Published - Apr 14 2023 |
Funding
The authors acknowledge Dr. Qifeng Wang and Qihua Chen for useful discussions. This research was sponsored by the Army Research Laboratory and was accomplished under Cooperative Agreement W911NF2120085. The views and conclusions contained in this document are those of the authors and should not be interpreted as representing the official policies, either expressed or implied, of the Army Research Laboratory, or the U.S. Government. The U.S. Government is authorized to reproduce and distribute reprints for Government purposes notwithstanding any copyright notation herein. This work made use of the MatCI and CLaMMP Facilities, which receive support from the MRSEC Program (NSF DMR-1720139) of the Materials Research Center at Northwestern University.
Keywords
- disulfide
- dynamic covalent bonding
- epoxy thermoset
- fracture mechanics
- mechanochromism
- polymer glass
- toughness
ASJC Scopus subject areas
- Process Chemistry and Technology
- Polymers and Plastics
- Organic Chemistry