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Abstract  

The effects of high pressure carbon dioxide (CO2) on the isotropic transition of three different amphiphilic di-block copolymers, PEOm-b-PMA(Az)n, namely PEO114-b-PMA(Az)40, PEO272-b-PMA(Az)46 and PEO454-b-PMA(Az)47, and on PMA(Az)30 homopolymer have been investigated by scanning transitiometry. Under CO2 pressure, the isotropic transition temperature decreased with the increase of pressure up to around 30 MPa due to CO2 sorption and increased above 40 MPa. Transition entropy of the isotropic transition indicated that the depression of the isotropic transition temperature was caused by the adsorption of CO2 into the azobenzene moieties and that the increase above 40 MPa was caused by the desorption of CO2 into the azobenzene moieties. Comparison between PEOm-b-PMA(Az)n copolymers and PMA(Az) homopolymer clarified PEO domain acted CO2 pathway to approach the equilibrium state rapidly.

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Abstract  

The effects of nitrogen (N2) pressure on amphiphilic di-block copolymer, PEO114-b-PMA(Az)40, were investigated by scanning transitiometry. The isotropic transition temperature increased with the increase of pressure above 20 MPa. The hydrostatic pressure effects evaluated with the Clapeyron equation were smaller than the value obtained by mercury as a pressurizing medium because the amount of absorbed gas decreases the volume change at the isotropic transition.

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Journal of Thermal Analysis and Calorimetry
Authors: S. Boyer, J-P. Grolier, L. Pison, C. Iwamoto, H. Yoshida, and T. Iyoda

Abstract  

The present work deals with the interactions between carbon dioxide, used as pressure medium, either in the gas state (GCO2) or in the supercritical state (SCCO2) and amphiphilic di-block copolymers PEOm-b-PMA(Az)n. The effect of pressure on the isotropic transition of the PEOm-b-PMA(Az)n copolymer was investigated using scanning transitiometry (ST). The experimental results were compared with those measured when using ‘relatively inert’ mercury (Hg) as pressure medium. Morphological observation of a PEOm-b-PMA(Az)n thin film submitted to SCCO2 was performed by atomic force microscopy (AFM) to investigate the nano-structure organization. These results indicate the possibility of modifying the nano-structure in a specific way depending on the CO2 physical state.

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