Kazuyuki Tachi

Effects of hydrophobic interactions on swelling of carboxylated core-shell structured latex particles

Carboxylated core-shell particles which contain carboxyl groups in the shell polymer swell in aqueous dispersion by electrostatic repulsion between carboxylate ions. Effects of hydrophobic interactions on the swelling of carboxylated core-shell particles were examined by measuring their diameters as a function of various hydrophobicities of the neutralizing amine, the shell polymer, and the dispersion medium. When the dispersion is neutralized by hydrophobic amine which does not contain a hydroxyl group, the swelling is promoted for low pH and suppressed for high pH with increasing the hydrophobicity of the amine. This result suggests that the amine is concentrated near the particle surface by hydrophobic attractions. This concentrated amine promotes dissociation of carboxyl groups of the shell polymer, but combines with dissociated carboxylate ion electrostatically just like a crosslinker. As the hydrophobicity of the amine increases, the amine becomes highly concentrated, and the dissociation of the carboxyl groups and crosslinking are promoted. The swelling is suppressed when the hydrophobicity of shell polymer increases, and that is promoted when the hydrophobicity of dispersion medium increases.

New Surface Treatment of Polymers by Simultaneous Exposure to Vacuum Ultra-Violet Light and Nanometer-Sized Particles

By focusing the strong vacuum ultra-violet absorption of carbon atoms, polymer surfaces were simultaneously exposed to vacuum ultra-violet light (VUV) and nanometer-sized particles. As a result, the adhesive properties of polymer surfaces were improved. The improvement of the polymer surface is caused by the creation of the bonds between nanometer-sized particles and carbon atoms of the polymer surfaces, which is supported by the theoretical calculation of core electron bonding energy. Despite the other UV treatment, the polymers themselves were not damaged or maintained their surface activations for more than one month. This result should expand new applications of polymers, and apply to almost all polymers scientifically and industrially.

Surface treatment of polymers by simultaneous exposure to vacuum uv and nanometer-sized particles in helium atmosphere

A new surface treatment for polymers in helium at atmospheric pressure for making bonds between surfaces and painting over polymer surfaces was demonstrated. In one-atmospheric helium gas, which was transparent for vacuum UV light at wavelengths between 60 and 80 nm, polymer surfaces were exposed simultaneously to vacuum UV (VUV) and ablated particles from the plasma on a carbon target irradiated with a high-intensity pulse YAG laser. Considering the breakdown threshold and VUV intensity, the optimum irradiation intensity of YAG laser was about 4 GW/cm2. The adhesive properties of polymer surfaces exposed to VUV and particles ablated by 4 GW/cm2 laser irradiation in one-atmospheric helium gas were improved. This result should expand new applications of polymers, and apply to almost all polymers scientifically and industrially.