Zeki Y. Al-Saigh

Review: Inverse Gas Chromatography for the Characterization of Polymer Blends

Abstract Inverse gas chromatography (IGC) has been proven to be useful for the characterization of polymer blends in terms of polymer-polymer interaction parameters, polymer-solute interaction parameters, solubility parameters, molar heat of sorption and mixing, melting point depression as an indicator of miscibility, contact energy parameters, and surface characterization. A complete treatment of the theories of polymer blend solution and IGC are illustrated, and the general use of the IGC method is reviewed.

Surface and thermodynamic characterization of conducting polymers by inverse gas chromatography: I. Polyaniline

The surface thermodynamic characteristics of both doped polyaniline (PANI-HEBSA) and the non-conducting form (PANI-EB) were investigated using inverse gas chromatography. Fourteen solutes were injected into two separate chromatographic columns containing PANI-EB and PANI-HEBSA. All solutes interacted strongly with the conducting form PANI-HEBSA; in particular, undecane and dodecane showed stronger interaction due to the increase of the dispersive forces. Methanol and ethanol showed stronger H-bonding with the conducting form than propanol and butanol. A curvature was observed for acetates and alcohols with a maximum of around 145 degrees C as an indication of a phase change from a semicrystalline to amorphous phase. DeltaH(l)s value increased considerably (-3.35 to -46.44 kJ/mol) while the deltaH(l)s for the undoped PANI (PANI-EB) averaged about -0.03 kJ/mol. PANI-EB-alkane interaction parameters were measured and ranged from +0.40 to +1.50 (endothermic). However, PANI-HEBSA showed an exothermic behavior due to the polar surface (-1.50 to +1.2). Interaction parameters decreased as the temperature increased and are characteristic of the strong interaction. The dispersive surface energy of the non conducting PANI-EB ranged from 29.13 mJ/m2 at 140 degrees C to 94.05 mJ/m2 at 170 degrees C, while the surface energy of the conducting PANI-HEBSA showed higher values (150.24 mJ/m2 at 80 degrees C to 74.27 mJ/m2 at 130 degrees C). Gamma(s)d values for PANI-EB were found to be higher than expected. The trend of the gamma(s)d change direction is also surprising and unexpected due to the thermal activation of the surface of the polymer and perhaps created some nano-pores resulting in an increase in surface energy of the non-conducting form.

Characterization of poly(ethyl methacrylate) by inverse gas chromatography

Abstract The inverse gas chromatography (i.g.c.) method was applied to poly(ethyl methacrylate) (PEMA) as a method for polymer characterization. We have shown that the method was useful in obtaining meaningful thermodynamic data on PEMA-solvent systems, and information on the depolymerization of PEMA at a temperature close to its decomposition temperature. Three chemically different families were used to obtain some insights about PEMA-solvent interactions. PEMA was found to decompose above 245°C. However, above this temperature, the i.g.c. method can be utilized to detect the decomposition temperature. The PEMA-solvent interaction parameters and the free energy of mixing were found to be independent of the number of carbons in the series and temperature. The thermodynamic sorption functions for the sorption process of the three families of probes into PEMA solution were obtained and discussed in terms of their interactions with PEMA backbone. Furthermore, the contributions of CH 2 , CO and OH functional groups in the three series to the sorption process were also obtained. We found that the formation of hydrogen bonds between the CO group of PEMA and the OH group of the alcohols is stronger than the dipole-dipole interactions between PEMA and the carbonyl groups of the acetates and the dispersive forces between PEMA and the alkanes. The latter was shown to be the weakest among the three series, and alkanes were found to be non-solvents of PEMA.

Characterization of poly(vinyl methyl ketone) using the inverse gas chromatography method

The inverse gas chromatography method was applied to the semicrystalline polymer poly(vinyl methyl ketone) (PVMK). The method was able to provide valuable information on the thermodynamic and surface properties of PVMK. Thirteen solutes with different chemical properties were used. They provided information on the type and strength of the polymer-solute interactions which were attributed to the melting behavior of PVMK. The melting temperature of PVMK was detected with precision using solutes that interacted strongly with PVMK. The interaction parameters χ 12 of PVMK-alkanes over the temperature range 70-180°C were obtained and were shown to be independent of temperature and number of carbons in the alkane series. The dispersive contribution of the surface energy of PVMK was measured as a function of temperature. The values ranged between 29.00 and 18.00 mJ/m 2 . The molar heat of sorption and the molar free energy of adsorption were calculated.

Solubility and surface thermodynamics of conducting polymers by inverse gas chromatography. III: polypyrrole chloride.

Inverse gas chromatography, IGC, was applied to characterize conducting polypyrrole chloride (PPyCl) using twenty three solvents. IGC is able to reveal the change in the morphology, the strength of solvent-PPyCl interactions, thermodynamics parameters (χ12, Ω1(∞)), solvent and polymer solubility parameters, and molar heats of sorption, mixing and evaporation (ΔH1(s), ΔH1(∞), ΔH1(v)). The following solvents showed stronger interactions than others; yet, none of these solvents are good solvents for PPyCl: dodecane among the alkane family, tetrahydrofuran and methyl ethyl ketone among the oxy and keto group, dichloromethane among the chlorinated group up to 120°C and chloroform at 180°C, and toluene among the cyclic and aromatic group. Overall, the groups showed higher affinities to PPyCl are: acetates, oxy and cyclic, and chlorinated groups. Comprehensive solvents and PPyCl solubility parameters are obtained. The latter showed that PPyCl is not soluble in any solvent used.

Miscibility and surface characterization of a poly(vinylidene fluoride)‐poly(vinyl methyl ketone) blend by inverse gas chromatography

The miscibility of blends of semicrystalline poly(vinylidene fluoride)(PVF2) and poly(vinyl methyl ketone) (PVMK) along with surface characterization were investigated using the inverse gas chromatography method (IGC), over a range of blend compositions and temperatures. Three chemically different families, alkanes, acetates, and alcohols, were utilized for this study. The values of the PVF2-PVMK interaction parameters were found to be slightly positive for most of the solutes used, although some degree of miscibility was found at all compositions. Miscibility was greatest at a 50:50 w/w composition of the blend. The interaction parameters obtained from IGC are in excellent agreement with those obtained using calorimetry on the same blends. The calculated molar heat of sorption of alkanes, acetates, and alcohols into the blend layer reveal the impact of the combination of dispersive and hydrogen bonding forces on the interaction of solutes with the blends backbone. The dispersive component of the surface energy was found to range from 18.70–64.30 mJ/m2 in the temperature range of 82–163 °C. A comparison of the blends surface energy with that of mercury and other polymers is given.

Photochemistry of 1,1,1-trifluoro-3-bromoacetone

Upon irradiation with ultra violet light, trifluorobromoacetone decomposes into CF3· and CH2Br· radicals and carbon monoxide when irradiated at a wavelength of 305 nm, and into CF3COCH2· and Br· radicals when irradiated at a wavelength of 225 nm. The two modes of decomposition are associated with absorption due to the carbonyl and CBr groups in the molecule.