長鎖ビニル重合体を一成分として含む混合単分子膜の研究 (第1報)

表面圧-面積曲線による分子間相互作用の検討

抄録

The binary mixed monolayers of polyvinyl stearate with various long chain compounds, such as 1-hexadecanol, 1-octadecanol, stearic acid, vinyl and ethyl stearates, have been studied by pressure-area characteristics, with some interests in the resistance of these mixed monolayers to water evaporation. In all cases, the mixed monolayers showed remarkable condensation effect. For the mixed monolayers of polyvinyl stearate with 1-hexadecanol, 1-octadecanol and ethyl stearate, the mean areas per hydrocarbon chain exhibited minima, while the compressional moduli exhibited maxima, in the particular compositions where the mole fractions (monomer unit) of polyvinyl stearate were 0.3 to 0.4.
From the data of pressure-area isotherms, the apparent excess free energies of mixing ΔGex were evaluated, using the area and the mole fraction in monomer unit for the polymeric component, on the assumption that each monomer residue behaves independently as a kinetic unit. Negative deviations were largest at nearly the same composition as the above, where the values of ΔGex were obtained in the range of -40 to -80 cal/mole at 20 dynes/cm. On the other hand, for the mixed monolayer of 1-octadecanol with ethyl stearate which can be considered to be equivalent to the repeating unit of polyvinyl stearate, negative deviation was rather small. Thus, the above-mentioned remarkable condensation effect seems to be characteristic of the mixed monolayers in which one component is the comb-like polymer with long side chains while the other is monomeric long chain compounds. It has been considered that the penetration of long chain alcohol or acid into the two-dimensional coil of polyvinyl stearate in the monolayer causes a decrease of the free area of the polymer and closer packing of the hydrocarbon chains of the both components. Contribution of hydrogen bonding between the polar groups seems to be rather small.