Polymer Microstructures: Modification and Characterization by Fluid Sorption

Abstract

Polymer micro-organization can be modified by a combination of three constraints, thermal, hydrostatic, and fluid sorption. In selecting the fluid's nature, chemically active or inert, and its physical state, liquid or supercritical, new "materials" can be generated. In addition, the interplay of temperature and pressure allows tailoring the obtained material structure for specific applications. Several complementary techniques have been developed to modify, analyze, and characterize the end products: scanning transitiometry, vibrating-wire (VW)-PVT coupling, thermoporosimetry, and temperature-modulated DSC (TMDSC). The great variety of possible applications in materials science is illustrated with different polymers which can produce materials from soft gel to rigid foams when submitted to fluid sorption, typical fluids being methane or a simple gas (CO 2 or N 2 ). Absorption of an appropriate fluid in a crosslinked polymer leads to a swelling phenomenon. Thermoporosimetry is a calorimetric technique developed to measure the shift by confinement of thermal-transition temperatures of the swelling fluids, which can be currently used solvents or mercury.Application of thermoporosimetry to a swollen cross-linked polymer allows calculation of the mesh size distribution and evaluation of the degree of reticulation of the polymer. The same technique can be applied to characterize the pore size distribution in a foamed polymer.

Water as a morphological probe to study polymer–filler interfaces: an original application of thermoporosimetry

“…For cyclohexane, the conversion of the crystallization thermogram of the confined liquid into pore size distributions was performed using the equations published in a previous work. 24 A specific program was used for the thermoporosimetry experiment with a drying step which allows observation of the progressive desorption of the confined solvent and thus estimation of the size of the un-swelled mesh. Successive cooling programs were performed including drying periods between each cooling.…”

Coagulation dimension of freezable bound solvent in isotactic polypropylene/o-dichlorobenzene gel

“…Recently, Nedelec et al 17 reported that the coagulation radius estimated by differential scanning calorimetry (DSC) measurements can be described by an exponential function. [15][16][17][18][19] The former relationship corresponds to the first-order Taylor polynomial of the latter one. By using the first-order approximate function, 20,21 we reported the coagulation dimension of water in a PVA hydrogel formed from freeze/thaw cycles.…”