Chemistry Reference
In-Depth Information
thermo-isolated hoses. The H¨ber cryostat/thermostat connected to the calorimeter
can be operated over the temperature range from
90 to 200
C, with ± 0.02
C
10
C, and has cooling power at 0,
temperature stability at
20,
40,
60 and
80
C of 5.2, 5, 4.2, 3.1, and 0.9 kW, respectively.
The maximum delivery of the circulating pump is 40 L min
1
and the maximal
delivery pressure is 1.5 bars. The cryostat is microprocessor-controllable and
equipped with an RS232 interface. The cryostat is PC-controlled thanks to Lab-
worldsoft 3.01 graphical software. The software allows building the temperature
program (up to 99 sequences), controls the temperature with high accuracy, and
performs data acquisition into a file, with a selectable frequency.
A striking (patented [
25
]) feature of scanning transitiometry is, for the investi-
gation of gas polymer interactions, the possibility to use different pressurizing or
pressure-transmitting hydraulic fluids. Depending on the type of measurement, the
sample under investigation can either be confined in a closed supple ampoule, itself
immerged in the hydraulic fluid, or positioned directly in contact with the hydraulic
fluid. In the latter case, the energetic interaction upon the possible sorption of the
fluid with the sample can be directly evaluated and documented.
Transitiometry is at the center of different types of utilization since, with such
techniques, bulk properties, transitions, and reactions can all be advantageously
studied. In the case of polymer synthesis, a scanning transitiometer was used as an
isothermal reaction calorimeter, the advancement of a polymerization reaction
being accurately monitored through rigorous control of the thermodynamic para-
meters [
27
,
28
]. To gather additional information, the measuring cell can be
coupled with other analytical devices (e.g., on-line FTIR, particle sizing probes,
turbidity probes, pH or other ion selective probes) [
29
]. For studying chemical
reactions, the scanning calorimeter has been also used as a temperature oscillation
calorimeter, and the high-pressure cells replaced by specially designed reaction
vessels. These vessels allow stirring, different dosing profiles for one or two
reactants, and can accommodate a small optical probe coupled to a miniaturized
spectrophotometer (for more details see [
28 31
]).
3 Gas-Polymer Interactions and Practical Applications
The performance and advantages of combining scanning transitiometry and the gas
sorption swelling technique are well demonstrated by typical applications in sev-
eral important fields: (a) transitions of polymer systems under various constraints
(temperature, pressure, gas sorption) including first-order phase and glass tran-
sitions; (b) polymer thermophysical properties and influence of gas sorption (blis-
tering phenomena); (c) thermodynamic control of molecular organization in
polymeric structures (foaming process, self-assembling nanostructures). Some
illustrative examples have been chosen for their impact in polymer science, in the
petroleum industry, and in microelectronics.
