Hydrocarbon interaction parameters

It has been demonstrated that the length of the hydrocarbon solvent molecule can have a significant impact of the stability of sterically stabilized nanoparticles [24, 30]. The solvation of a sterically stabilized nanoparticle depends on the interaction parameter, %, between the solvent and the ligand [25, 30-33], such that... 

The above values are applicable only in the limiting case of infinite dilution. The interaction parameter varies with the volume fraction of polymer network as has been demonstrated for the PDMS-benzene system by Flory (47) and PDMS-methyl ethyl ketone, PDMS-methyl isobutyl ketone, PDMS-ethyl-n-butyl ketone, and PDMS-diisobutyl ketone by Shiomi et al. (48). Theoretically calculated and experimentally observed values of X as a function of volume fraction of polymer are given for PDMS in alkanes, aromatic hydrocarbons, and dimethyl siloxane oligomers by Gottlieb and Herskowitz (49). In the case of PDMS-alkanes, x was practically independent of the volume fraction of polymer. 

Although being qualitatively in agreement with experimental results, disagreements between experiment and theory remain. Besides the composition, /a, and the total degree of polymerization, N, all theoretical works refer to the segmental interaction parameter x This parameter can be estimated from a relationship to the solubility parameters. The ODT as a thermodynamic measure of the incompatibility was used to compare a set of symmetrically composed diblock copolymers from different hydrocarbons, polydimethyl-siloxane and poly(ethylene oxide) (PEO) [33]. While the behaviour of hydrocarbon diblock copolymers was successfully described by a consistent set of solubility parameters, this procedure failed for systems containing PEO. The... 

Chiu, S. W., Clark, M. M., Jakobsson, E., Subramaniam, S. and Scott, H. L. (1999). Optimization of hydrocarbon chain interaction parameters application to the simulation of fluid phase lipid bilayers, J. Phys. Chem. B, 103, 6323-6327. 

For ternary and higher order mixtures, we have usually assumed that the interaction parameters for the non-water binary pairs in the water rich phase are identical to the vapor (hydrocarbon rich liquid phase) interaction parameters. Some work has been done on changing all water phase interaction parameters we concluded that predicted results were not improved enough to warrant the expenditure of time required to develop the additional parameters. A third interaction parameter for the hydrocarbon rich liquid could also be determined. Again, our work indicated that little improvement resulted from using this third parameter. Additional work is being done on both points. 

A similar strategy was used to develop the PFGC-MES equation of state parameters for describing the behavior of methanol hydrocarbon acid gas water systems. Multiple phase binary interaction parameters were used as required. Again, these second phase binary interaction parameters were usually not temperature dependent. 

Other Hydrocarbon - Water Systems. Interaction parameters were generated for the benzene - water system. The data used were those of Scheffer (31 ) > Rebert and Kay 35) > and Connolly... 

J. As with the alkane - water systems, the interaction parameters for the aqueous liquid phase were found to be temperature - dependent. However, the compositions for the benzene - rich phases could not be accurately represented using any single value for the constant interaction parameter. The calculated water mole fractions in the hydrocarbon - rich phases were always greater than the experimental values as reported by Rebert and Kay (35). The final value for the constant interaction parameter was chosen to fit the three phase locus of this system. Nevertheless, the calculated three-phase critical point was about 9°C lower than the experimental value. 

Interaction parameter was also generated for the hydrocarbon -rich phases of the n-octane - water system. The data of Kalafati and Piir (37j were used. There were no data available for the water - rich liquid phase for this binary. 

Experimental solubility data are available for some higher alkane - water systems (see, for example, Skripka et al., (38)). However, these data either cover only a very limited temperature range or contain results for one phase only. No attempt has been made to determine the interaction parameters for water - hydrocarbon systems where the hydrocarbon is larger than n-octane. 

Fractional Precipitation of Cellulose Triacetate. The reported partial or non-fractionation of cellulose triacetate from chlorinated hydrocarbons or acetic acid may be explained in terms of the polymer-solvent Interaction parameter x (1-11) The x values for cellulose triacetate-tetrachloroethane and cellulose triacetate-chloroform systems are reported (10,21) as 0.29 and 0.34 respectively. The lower values of x for such systems will result in a smaller or negative heat of mixing (AHm) and therefore partial or non-fractionation of the polymer in question results. 

Here, also we have extended (10) our treatment of synergism to 2-phase liquid systems and have derived equations that are completely analogous to those obtained for solutions in contact with air, when the nonaqueous phase is a hydrocarbon. The interaction parameter,... 

The carbon di oxi de/lemon oil P-x behavior shown in Figures 4, 5, and 6 is typical of binary carbon dioxide hydrocarbon systems, such as those containing heptane (Im and Kurata, VO, decane (Kulkarni et al., 1 2), or benzene (Gupta et al., 1 3). Our lemon oil samples contained in excess of 64 mole % limonene so we modeled our data as a reduced binary of limonene and carbon dioxide. The Peng-Robinson (6) equation was used, with critical temperatures, critical pressures, and acentric factors obtained from Daubert and Danner (J 4), and Reid et al. (J 5). For carbon dioxide, u> - 0.225 for limonene, u - 0.327, Tc = 656.4 K, Pc = 2.75 MPa. It was necessary to vary the interaction parameter with temperature in order to correlate the data satisfactorily. The values of d 1 2 are 0.1135 at 303 K, 0.1129 at 308 K, and 0.1013 at 313 K. Comparisons of calculated and experimental results are given in Figures 4, 5, and 6. 

The influence of size and shape on the diffusion of hydrophobic solutes was estimated by simulations involving artificial Lennard-Jones particles those intermolecu-lar interaction parameters were based on those for ammonia or oxygen, respectively. The results on the size dependence of diffusion confirmed that the membrane interior differs strongly from a bulk hydrocarbon. In the center of the bilayer, the excess free energy for hydrophobic Lennard-Jones particles remained low irrespective of the size of the particles. This can be explained by the large fraction of accessible volume in that region. 

Here, again, we start from compressible SCFT formalism described in Section 2.2 and consider a model system in which bulk polymer consists of "free" matrix chains (Ny= 300) and "active" one-sticker chains (Na= 100). Flory-Huggins interaction parameters between various species are summarized in Table 1. This corresponds to the scenario in which surfactants, matrix chains, and functionalized chains are all hydrocarbon molecules (e.g., surfactant is a C12 linear chain, matrix is a 100,000 Da molecular weight polyethylene, and functionalized chain is a shorter polyethylene molecule with one grafted maleic group). The nonzero interaction parameter between voids and hydrocarbon monomers reflects the nonzero surface tension of polyethylene. The interaction parameter between the clay surface and the hydrocarbon monomers, Xac= 10 (a = G, F, A), reflects a very strong incompatibility between the nonpolar polymers and... 

Charlet, G. Ducasse, R. Delmas, G., "Thermodynamic Properties of Polyolefin Solutions at High Temperature 2. Lower Critical Solubility Temperatures for Polybutene-1, Polypen-tene-1 and Poly(4-methylpentene-1) in Hydrocarbon Solvents and Determination of the Polymer-Solvent Interaction Parameter," Polymer, 22, 1190 (1981). 

Since the initial work of Smidsrod and Guillet numerous investigators have used I.G.C. to determine physicochemical parameters characterising the interaction of small amounts of volatile solutes with polymers Baranyi has shown that infinite dilution weight fraction activity coefficients, interaction parameters and excess partial molar heats of mixing can be readily determined with this technique. Partial molar heats and free energies of mixing, and solubility parameters of a wide variety of hydrocarbons in polystyrene and poly(methyl methacrylete) have been determined The temperature dependence of the interaction parameter between two polymers has also been studied... 

Schreiber and collaborators (44,4S) reported such compariscms of interaction parameters obtained by GC and static methods for poly(dimethyl siloxane) (44) and natural mbber (45). A summary of their results for hydrocarbon K>hites in poly(di-methyl siloxane) is given in Table 3 for both x (x ) d X12 interaction parameters. 

Schreiber, Tewari and Patterson 53) reported interaction parameters of more than 20 hydrocarbons in linear and branched polyethylenes, at temperatures above the melting point. The corresponding x parameters are given in Table 5. Despite the chemical identity of the components, substantial interaction parameters were obtained. This was attributed to the large contribution arising from the free volume dissimilarities of the components. Indeed it proved possible to correlate the magnitude... 

Tables 4 and 5 also list the values of the energy interaction parameters Tij for the alcohol/water and hydrocarbon/water systems. For the alcohol/water systems, the parameters were calculated for both dilute solutions of alcohol in water and dilute solutions of water in alcohol. For hydrocarbon/water systems, the calculations were carried out only for dilute solutions of hydrocarbon in water, because no experimental information could be found for the solutions of water in hydrocarbons. Figure 3 presents a plot of F12 versus the number of carbon atoms in molecules for normal alcohols and hydrocarbons.

For the prediction of the mixed-gas solubilities from the solubilities of the pure individual gases, the pressure dependence of the binary parameters ku is needed. The Peng—Robinson EOS was used to determine the binary parameters ku. The binary interaction parameter qi2 in the van der Waals mixing rule was taken from ref 28, where it was evaluated for the water-rich phases of water—hydrocarbon and water—carbon dioxide binary mixtures. The calculated binary parameters ku are listed in Table 1. One should note that, as expected for a liquid phase, the above parameters are almost independent of pressure, in contrast to their dependence on pressure in the gaseous phase near the critical point,... 

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