Probe-polymer interaction parameter

By applying the Flory-Huggins equations of polymer solutions to a ternary system with two polymers and one probe, the interaction parameter Xi can be related to the probe-polymer interaction parameters x" and Xu) and the polymer-polymer interaction parameter ( 23) by the following equation [41] ... 

The usefulness of inverse gas chromatography for determining polymer-small molecule interactions is well established (1,2). This method provides a fast and convenient way of obtaining thermodynamic data for concentrated polymer systems. However, this technique can also be used to measure polymer-polymer interaction parameters via a ternary solution approach Q). Measurements of specific retention volumes of two binary (volatile probe-polymer) and one ternary (volatile probe-polymer blend) system are sufficient to calculate xp3 > the Flory-Huggins interaction parameter, which is a measure of the thermodynamic... 

Earlier attempts at using IGC to characterize polymer blends were unsuccessful. The polymer-polymer interaction parameters evaluated were found to vary with the probe used (1-5). For this reason, the use of IGC for the study of blends has been severely... 

Guillet and coworkers (8-10) have determined the solubility parameter of polymers from the probe-polymer interaction coefficients. They separated the interaction parameter into entropic and enthalpic contributions, such that Xi2=X h+Xs to yield, in combination with Hildebrand s solution theory, the following expression ... 

Polymer-Polymer Interaction Parameter. Table I lists the probes used in this work and the numbers that correspond to those shown in the Figures. 

Fig. 11. Values of the polymer-polymer interaction parameters (%), determined by inverse-phase gas chromatography with different probes, for PVC/PCL blends as functions of PCL volume fractions taken from [72]...

Huang, J.-C. (2006) Anomalous solubility parameter and probe dependency of polymer-polymer interaction parameter in inverse gas chromatography. Eur. Polym. J., 42, 1000-1007. 

As a result of the Rowing interest in the GC route to obtain information on polymer-solute systems, a large body of data, activity coefficients and/or interaction parameters, has been reported. Polystyrene 51,59), poly(vinyl chloride) (60), polyethylene (60-62), poly(ethylene oxide) (65) and copolymers of ethylene with propylene and vinyl acetate (62) have been studied with a variety of probes. 

IGC was used to determine the thermodynamic miscibility behavior of several polymer blends polystyrene-poly(n-butyl methacrylate), poly(vinylidene fluoride)-poly(methyl methacrylate), and polystyrene-poly(2,6-dimethyl-1,4-phenylene oxide) blends. Specific retention volumes were measured for a variety of probes in pure and mixed stationary phases of the molten polymers, and Flory-Huggins interaction parameters were calculated. A generally consistent and realistic measure of the polymer-polymer interaction can be obtained with this technique. 

With careful experimented design, inverse gas chromatography can be a viable method for the determination of the polymer-polymer interaction coefficient B23. The variation of apparent B23 values with the probe is shown to be related to the chemical nature of the probe and not due solely to experimented error. A method is presented to allow the estimation of the true B23 value. Experiments were performed on a 50/50 blend of poly(epichloro-hydrin)/poly( -caprolactone) at several teqperatures. Polymer and blend solubility parameters were determined. 

Figure 1. Dependence of the polymer-polymer interaction coefficient B23 (cal/mL) on the solubility parameter of the probe (cal/mLyi for PCI/PECH 50/50 blend at 80 C.

It is postulated that a hypothetical probe, that has the same solubility parameter (cohesive energy) as the blend and does not exhibit any specific interactions with the blend components, yields the true polymer-polymer interaction coefficient. 

Since its introduction some years ago, inverse gas chromatography (IGC) has been recognized as a convenient route to the determination of thermodynamic interaction parameters for polymeric or other non-volatile stationary phases in contact with selected vapor probes (1,2). The principles of IGC experiments have also been extended to two-component stationary phases (3), thereby making it possible to specify thermodynamic interaction parameters for the components of polymer blends (4,5), as well as for filled polymers and other mu 11i-component systems. Despite these attractive features, limitations must by recognized on the general... 

In this section we address the question of accordance between coexistence conditions determined for polymer mixtures in the bulk and confined in thin bilayer films. Macroscopic samples with the size of ca. 1 mm are analyzed by Small Angle Neutron Scattering. It probes the compositional fluctuations away from binodal to yield the effective interaction parameter %SANs(bilayer films are studied by profiling techniques to yield concentrations < q and 2 at binodal. These are described by the composition dependent interaction parameter %(([>). In fact only the section of the relation %(([>) bounded by ( q and <(>2 is relevant as it describes the whole intrinsic profile of Fig. 2. 

A study by A.K. Sen and G.S. Mukheijee (Sen and Mukheijee, 1993) reported the use of inverse gas chromatography to investigate the thermodynamic compatibility of blends of PVC and nitrile rubber (NBR) as a function of blend composition and acrylonitrile content of NBR. The values of the polymer-polymer thermodynamic interaction parameters and the solubility parameter of the polymers and then-blends were determined with the help of the measured retention data for various polar and nonpolar probes in the pure and mixed stationery phases of these polymers. The two polymers exhibited fair compatibility which increased with increasing content of acrylonitrile in NBR. 

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