It has been well established3-7 that gas-liquid chromatography (glc) can give accurate thermodynamic data on binary solutions where the components differ considerably in volatility or molecular weight. The substance of lower molecular weight (component 1) is injected into the moving gas phase and dissolves at effectively infinite dilution in the stationary liquid phase. This is formed by the higher molecular weight material, for example,3 squalane, biphenyl, dinonyl phthalate, glycerol, or the higher «-alkanes such as Cíe, C24, C36, etc. The convenience of the technique is such that activity coefficient data have already been obtained for hundreds of systems. In contrast, activity data are available for far fewer high polymer systems, in part certainly because of the need to use the laborious vapor sorption technique. While that technique gives activity
The surface properties of cellulose fibers have been modified by heat treatment, by silane coupling agents, and by maleated polypropylene grafts. The effectiveness of these methods has been evaluated by electron spectroscopy (ESCA), by contact angle measurements, and by inverse gas chromatography. The latter analyses yielded information on the fibers' acid/base interaction potential. Cellulose was found to be amphoteric, with prevalent acidic properties. Heat and chloro-silane treatments accentuated acidity, while amino-silane treatment produced net basicity in the fiber surface. Modification with rnaleated polypropylene reduced specific interactions and converted the fiber to a predominantly dispersion-force solid. The modified fibers were used in composites with polypropylene (neutral), polystyrene (base), and chlorinated polyethylene (acid) as matrix. Stress/strain and dynamic mechanical parameters were found to vary with acid/base interactions between polymer and fiber, significant improvements being noted in elastic and storage moduli, in tensile strength and elongation. In polypropylene, properties were unaffected by acid/base considerations. Acid/base forces, not necessarily dominant, merit consideration in the design of surface modification strategies intended to optimize composite mechanical properties.
This paper examines the applicability of inverse gas chromatography (IGC) to the quantification for polymer substrates of electron acceptor-donor (or Lewis acid-base) interactions. Polycarbonate is used as the reference stationary-phase material. Various options have been compared for the graphical representation of experimental data leading to the evaluation of acid-base contributions, and preference among these was accorded on the basis of the convenience and breadth of applicability. From the temperature dependence of these acid-base contributions, the enthalpies of acid-base interaction have been determined. These were found to correlate with donor and new acceptor numbers, both in thermodynamically consistent units. Parameters expressing the ability of the polycarbonate surface to accept or to donate electrons may now be compared on an unequivocal basis. The polymer may be described as being amphoteric but with predominant basicity.
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