The Effect of Surface Adsorption on Gas Chromatographic Measurements Near Polymer Melting Transitions

Determination of Crystallinity by Gas Chromatography. Effect of Curvilinearity of Retention Diagrams

“…The specific retention volume is related to the polymer-solute properties by the expres-sion16 •17 In Vg = In [273.16 /( 1 1)" ,? 1] -(p?/RT)(Bu -VJ + (P0J¡/RT)(2B1S -VO (8) where (ai/itii)"_is the infinite dilution weight fraction activity coefficient, p?, Vlf and Mi are the vapor pressure, molar volume, and molecular weight of the solute, Bn and B13 are the second virial coefficients, R is the gas constant, T is the temperature, and J\ is given by eq 2. For a retention diagram to be linear, the value of the derivative, d In Vg/d (1/71), must be constant at all temperatures.…”

Analysis of interactions in multicomponent polymeric systems: The key-role of inverse gas chromatography

“…The approach of Dorris and Gray [105,107,115,119,120] is similar to that of Fowkes. This approach involves the use of molecular surface areas to elucidate the dispersive surface free energies, derived via the dispersive component of the work of adhesion.…”

Peer Reviewed: Characterizing Polymers by MPC

“…These points are marked with arrows in Figure 1 and vary over a range of 40 °C The T determined from differential scanning calorimetry for this narticular batch of PMMAwas 90-100 °C So ii this snerifir case the hydrocarbon probe 2-butanone produced the most reliable from the van't Hoff plot This probe dependence is a commonly observed phenomenon with MPC (8) and brings into question the idea of simple ad/absorption processes as the dominant retention mechanisms. Some investigators, most recently Romdhane and coworkers (9), have even suggested that absorption of the solute into the bulk polymer was the only retention mechanism operative in polymeric systems and that the characteristic shape of the van't Hoff plots was caused solely by the variation of the diffusion coefficient of the probe in the polymer with the temperature and physical state of the polymer In particular it was suggested that the controlling factor was the ratio of the carrier gas flow (which determines the contact time of the solute with the polymer) to the diffusion coefficient (11). If this ratio is low, ,hat ts, if the flow rate is low and the diffusion coefficient high, then the elution peaks would be symmetric and the retention times high; on the other hand, if the ratio is high, then the peaks would be asymmetric (because of slow diffusion) and the retention times low.…”