(774a) Preparation and Characterization of Highly Stable Organic Glasses (Or how to make a million-year-old glass in ten minutes)

The prevailing view in the literature has been that physical vapor deposition produces unstable glasses.  We show that slow depositions onto substrates held near 0.85 T_g can produce exceedingly stable glasses, likely the most stable glasses ever produced in a laboratory.  Producing similar glasses by slowly cooling a liquid would require at least thousands of years.  A mobile surface layer (~ 2 nm) at the glass surface allows rapid equilibration of incoming molecules even at temperatures where bulk relaxation is very slow.  We demonstrate that vapor-deposited glasses can have low enthalpies, low heat capacities, high densities, high mechanical moduli, and a high resistance to vapor uptake.  These materials have some surprising properties and allow us to explore fundamental features of amorphous solids.  They may also prove useful in thin film technologies such as organic photovoltaics, OLEDS, and next-generation photoresists.