This paper presents results of normal hardness, plasticity index and elastic modulus for a selection of organic polymers (a poly(methylmethacrylate), PMMA, a poly(styrene), PS, a poly(carbonate), PC, and an ultra-high molecular weight poly(ethylene), UHMWPE) obtained using the contact compliance method. The paper describes in detail the dependence of the imposed penetration depth, the maximum load and the deformation rate upon the hardness and elastic modulus values for these polymeric surfaces; typical penetration depths range from about 10 nm to m where the imposed loads are less than 300 mN. The results show a considerable strain-rate hardening effect for the present systems and possibly a peculiarly harder response of these materials at the near-to-surface (submicron) layers. The paper includes considerations of a practical nature which are drawn in order to overcome some intrinsic limitations of this technique when it is used for polymeric surfaces, especially for a creeping phenomenon which may be observed at the incipient unloading experimental segments. The appropriateness of using a tip calibration constructed upon hard substrates when indenting polymers is reviewed at the conclusion of the paper.

An in situ ATR (attenuated total reflectance)-IR study of CO 2 dissolved in two ionic liquids at high pressures has demonstrated the effects of the anionic species of the ionic liquids on the molecular state of the dissolved CO 2 .

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The CO2 sorption and the consequent swelling of un-cross-linked poly (dimethylsiloxane) (PDMS) have been measured simultaneously at high pressure using in-situ ATR (Attenuated Total Reflectance)−IR spectroscopy. The absorbance of the ν3 (2335 cm-1) band of CO2 dissolved in PDMS was used to determine quantitative sorption data. The absorbance of the IR band of PDMS was used to calculate the polymer swelling. Data at 25 °C and 50 °C for pressures up to 12 MPa are reported and compared to literature values. A shift of the δ(CH3) band of PDMS (at 1259 cm-1) was observed with the increase of sorbed CO2 and was related to the swelling of the polymer. This is a novel use for high-pressure in-situ ATR−IR spectroscopy, which allows the simultaneous measurement of gas sorption and polymer swelling and provides molecular-level insight into the behavior of polymers under high-pressure or supercritical CO2.

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