Copolymer characterization by surface tension

Abstract

synopsisThe use of surface tension measurements is proposed as a simple method for the determination of copolymerization ratios. The procedure depends on the parachor of the copolymer in the liquid state (n), which is defined by II = II,for solutions and II = [ D P ] Do for liquid or molten polymers, where II, is the parachor of the solvent of molecular weight M,; w p and w, are the weights of the polymer and solvent in solution; while IIo and Mo are the parachor and molecular weight of the repeating unit of the copolymer, respectively. The validity of this relationship is demonstrated by analysis of the surface tension properties of liquid silicone polymers, polystyrene-Decalin solutions, and molten polymers as well as by the calculation of the composition of some characterized tetrahydrofuran-propylene oxide copolymers. The application of surface tension measurement is also suggested as a means of estimating the degree of chain branching in a polymer.The establishment of the ratio of the constituent units in a copolymer is a common problem often encountered in macromolecular research. While the complete armamentarium of modern analytical chemistry can be brought to bear to resolve such questions, the procedures required may be cumbersome and tedious or they may involve the use of costly instrumentation not always readily ac~essible.~The simple physical measurement of the surface tension4J of a solution of the copolymer or the molten material is now proposed as a rapid, straightforward and inexpensive technique for securing this information without destruction of the sample. Thus, for example, rather precise (=k0.250/,) determinations of surface tensions can be made using the ubiquitous analytical laboratory balance. The overall procedure ultimately depends on the evaluation of the parachor II of the copolymer. The parachor was originally introduced as a physical constant by Sugden6 nearly half a century ago and defined by eq. (l), in which y is the surface tension of a substance of molecular weight M having a density of D L and d , for the liquid and vapor, respectively: 999

Plastic Sulfur Stabilization by Copolymerization of Sulfur with Dicyclopentadiene

“…It has been shown for silicone polymers that as the viscosity increases from an increase in molecular weight, the surface tension increases (27). A "step growth copolymerization mechanism," as mentioned earlier for the sulfur-DCP solutions, will have an increase of molecular weight with time, and the surface tension behavior appears to support this mechanism.…”

Molybdenum/Tungsten‐Based Heteropoly Salts in Oxidations

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Chemical foaming extrusion of poly(lactic acid) with chain-extenders: Physical and morphological characterizations

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