The properties of glasses strongly depend on the path to glass formation. Low energy, ultra-stable organic molecular glasses can be formed by physical vapor deposition. This route to producing ultra-stable glasses is not amenable to polymers. As such, the formation of low energy, ultra-stable polymer glasses have not been realized. The first objective of this CAREER award is to explore Matrix Assisted Pulsed Laser Evaporation (MAPLE) as a route to produce low-energy, ultra-stable polymer films. Processing parameters to be explored include growth rate (both instantaneous and average), substrate temperature, and kinetic energy of the depositing molecule. The stability, morphology, and mechanical properties will be characterized for all films. The second objective of this CAREER is to explore the mechanism of stable glass formation. Here, new experiments are proposed to explore the relationship between stable glass formation and surface mobility. First, the stability of polymer glasses that exhibit different enhanced surface mobility will be compared. Second, the stability of polymer films formed with different surface area/volume ratios will be compared. Third, a unique fluorescence multilayer approach that will allow for the direct measurement of free surface stability and energy-landscape surface will be developed. Fundamental questions this proposal will address include: Do films with greater surface mobility form more stable glasses? Are surface molecules able to explore lower energy states?
NON-TECHNICAL SUMMARY:
The work addresses fundamental questions concerning low-energy, stable glass formation, and, ultimately, the work may someday provide guidelines for the development of polymer glasses with unmatched thermal and kinetic stability. This proposal will explore one possible application of stable polymer glasses as ultra-barrier membranes. Other potential applications of these materials include 1) displays based on organic light-emitting diode technology, possessing enhanced stability to environmental factors (e.g., humidity, temperature fluctuations), and lower power consumption, 2) organic electronics with greater morphological stability, and 3) coatings and protective skin layers exhibiting greater resistance to contaminants. The new discovery of low energy, stable glasses will be incorporated into a new undergraduate/graduate elective course on the glass transition. The proposed research will be accomplished by a diverse team of high school, undergraduate and graduate students. This CAREER award outlines a unique 4-tier educational and outreach program to increase the number of underrepresented minorities and students from economically disadvantaged backgrounds interested in science, obtaining STEM degrees, and participating in academic research. The outreach program is designed to promote scientific involvement at all levels of a scientific career path.
