The effects of physical aging on the solubility, diffusivity, and permeability of propane and n‐butane in a hydrocarbon‐based disubstituted polyacetylene, poly(4‐methyl‐2‐pentyne) (PMP), were studied. As the relative pressure of propane and n‐butane increased, the solubility of both hydrocarbons increased. Like other glassy polymers, the sorption isotherms for propane and n‐butane in all PMP films were concave to the relative pressure axis, indicating dual‐mode sorption behavior. The diffusion of propane and n‐butane in PMP followed typical Fickian diffusion in a plane sheet. The propane diffusivity in both the unaged and aged films increased with increasing concentration of propane sorbed in the film. The n‐butane diffusivity in aged films also increased with increasing n‐butane concentration. However, unaged films showed the opposite behavior: the diffusivity decreased with increasing n‐butane concentration. These diffusion phenomena are a consequence of the interplay between thermodynamic and mobility factors. The permeabilities of propane and n‐butane decreased monotonically with increasing penetrant concentration, similar to the behavior observed in other common glassy polymers. The relaxation of the nonequilibrium excess free volume in PMP films induced the decrease in both solubility and diffusivity. As a result, the permeability of propane and n‐butane in PMP decreased upon physical aging. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2407–2418, 2004

We report a method to modify the surface of size-controlled ink particles (SIPs), consisting of natural eumelanin isolated from ink sacs of Sepia officinalis, through simple chemical reactions. The carboxyl group on the SIP was replaced with an amino group using cationization reagents. The original SIPs have a highly negative potential of −50.8 ± 0.6 mV. This value can be modified by cationization reagents. Increases in the surface potentials of the SIPs decreased the effect of blocking the aggregation through electrostatic repulsion. The original SIPs were repelled on negatively charged surfaces but adsorbed on positively charged surfaces. The opposite result was obtained in SIPs modified with cationization reagents. The specific interaction between the carboxyl group and the amino group might play a more important role than the overall electrostatic interactions at neutral pH. The results of this study should serve in the development of hair colorants utilizing SIPs.