Pressure, temperature, and thickness dependence of CO2-induced devitrification of polymer films.
The glass transition temperature is known to increase with decreasing film thickness h for sufficiently thin poly(methyl methacrylate) films supported by silicon oxide substrates. We show that this system undergoes a CO2 pressure-induced devitrification transition, P(g), which is film thickness dependent, P(g)(h)=DeltaP(g)+P(bulk)(g). P(bulk)(g) is the bulk glass transition and DeltaP(g) can be positive or negative depending on T and P. The phenomenon of retrograde vitrification, wherein the polymer exhibits a rubbery-to-glassy-to-rubbery transition upon changing temperature isobarically, is also shown to occur in this system and it is film thickness dependent.
Pham
Joseph Q
JQ
Graduate Program in Materials Science and Engineering, University of Texas at Austin, Austin, TX 78712, USA.
Sirard
Stephen M
SM
Johnston
Keith P
KP
Green
Peter F
PF