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An electrospray technique for hyperquenched glass calorimetry studies: Propylene glycol and di-n-butyl phthalate
 

Summary: An electrospray technique for hyperquenched glass calorimetry
studies: Propylene glycol and di-n-butyl phthalate
Li-Min Wang a
, Steve Borick b
, C. Austen Angell a,*
a
Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ 85287-1604, United States
b
Department of Chemistry, Scottsdale Community College, Scottsdale, AZ 85256, United States
Abstract
We describe an electrospray technique for in situ preparation, for differential scanning calorimetry study, of samples of molecular
liquids quenched into the glassy state on extremely short time scales (hyperquenched). We study the cases of a hydrogen-bonded liquid,
propylene glycol, PG and a Van der Waals liquid, di-n-butyl phthalate DBP. Using a fictive temperature method of obtaining the tem-
perature dependence of enthalpy relaxation, we show that the electrospray method yields quenching rates of $105
K/s, while the more
common method, dropping a sealed pan of sample into liquid nitrogen, yields only 120 K/s. These hyperquenched samples start to relax,
exothermically, far below the glass temperature, at a temperature (0.75Tg) where the thermal energy permits escape from the shallow
traps in which the system becomes localized during hyperquenching. This permits estimation of the trap depths, which are then compared
with the activation energy estimated from the fictive temperature of the glass and the relaxation time at the fictive temperature. The trap
depth in molar energy units is compared with the `height of the landscape' for PG, the quasi-lattice energy of the liquid based on the

  

Source: Angell, C. Austen - Department of Chemistry and Biochemistry, Arizona State University

 

Collections: Materials Science; Chemistry