▣ Special Seminar ▣
- Topic: Control of molecular orientation, thermal stability, and photochemical stability in vapor-deposited organic glasses
- Speaker: Mark Ediger (University of Wisconsin-Madison / Department of Chemistry)
- Date: 2016. 9. 30(Fri) 16:00~
- Venue: KAIST Applied Engineering B/D(W1) #1317
- Host: Prof. Sang Ouk Kim
We have used physical vapor deposition and the mobility of glassy surfaces to prepare what are likely the most stable glasses on the planet.(1) These materials have the properties expected for “million-year-old” glasses, including high density and high mechanical moduli.(2) Surprisingly, these glasses “melt” like crystals, with a constant velocity transformation front.(3) In addition, they resist photochemical degradation better than liquid-cooled glasses. Molecular orientation in vapordeposited glasses can be highly anisotropic.(4) These properties all depend systematically on the substrate temperature during deposition and can be measured efficiently with high throughput spectroscopic ellipsometry.(5)
The interesting properties of vapor-deposited glasses arise from the high mobility of glass surfaces. During deposition, molecules near the free surface have the opportunity to sample many different packing arrangements. This mechanism allows the molecular orientation in vapor-deposited glasses to be predicted from molecular dynamics computer simulations(4, 6) and could be useful for optimizing the performance of organic light emitting diodes (OLEDs).