Multi-scale degradation analysis of soft materials
With the growing awareness of global environmental issues, including the SDGs goals, the “long-term use of materials” is becoming more important. Efforts in the field of soft materials, which can also lead to the problem of waste plastics, will be viewed with greater scrutiny than ever before. In particular, it is important to understand the “degradation phenomenon” of soft materials for industrial use, which is the change in physicochemical properties over time that results in the failure to meet performance requirements.
Degradation phenomena start with microscopic degradation reactions, and the resulting changes in molecular chain morphology, such as chain scission and crosslink formation, change the internal microstructure of the material. Ultimately, these microscopic changes accumulate and scale up, leading to the deterioration of macroscopic properties. In order to understand the full picture of such degradation mechanisms, comprehensive and multifaceted material analysis across scales is essential. We have been analyzing the degradation of various polymeric materials subjected to photo (ultraviolet) and thermal degradation by using “multi-scale degradation analysis,” which is a series of protocols for understanding the picture of material degradation.
- T. Ishida, R. Kitagaki, H. Hagihara, Y. Elakneswaran Polym. Test., 96, 107123 (2021).
- T. Ishida, R. Kitagaki, R. Watanabe, H. Hagihara, Y. Elakneswaran, H. Shinzawa Polym. Degrad. Stab., 179 109242 (2020).
- T. Ishida, R. Kitagaki, S. Yamane, H. Hagihara Polym. Degrad. Stab., 162, 85-93 (2019).
Kinetics of chemical reacions and time evolution of network architecture
Thermosetting resins and polymer gels with a network structure have a variety of applications and are used in many situations. The relationship between the reaction dynamics and the internal network structure is naturally important, and has been studied since the “gelation theory” by Flory and Stockmayer in the 1940’s up to today. We are studying both the process of network “creation” by cross-linking reaction and the process of network “collapse” by molecular chain breakage due to degradation. The combination of classical network theory, in which the reaction rate of bonds is a variable, and the kinetic analysis of the assumed reaction mechanism is a powerful tool for understanding the time evolution of network architecture in various systems. We have shown that degelation, which is caused by network disorganization due to molecular cleavage, can trigger large-scale structural transformation. We believe that this is the “structural” material life of resin materials with network structures, and we are continuing to try to validate this from various perspectives.
- T. Ishida, E. Richaud, M. Gervais, A. Gaudy, R. Kitagaki, H. Hagihara, Y. Elakneswaran Prog. Org. Coatings, 163, 106654 (2022).
- T. Ishida, R. Kitagaki, H. Hagihara, Y. Elakneswaran Polymer, 186, 122035 (2020).
Multi-scale simulation for polymer aging: from molecular dynamics to macroscopic properties
In recent years, materials integration (MI) has been widely practiced to accelerate materials development by feeding back computational material properties and performance to the materials development process through theoretical models and simulations. This is also known as data-driven materials science, and materials informatics is included in MI.
In order to accelerate the development of materials that can be used for a long time, it is necessary to construct a “multi-scale degradation simulation platform” that can reproduce the changes in molecular motion associated with material degradation, i.e., changes in the nanoscale dynamics of molecular chains, on a computer. We are investigating the construction of a platform with a series of simulation engines that can effectively describe the phenomena occurring at each scale from microscale to macroscale.