Modification of aqueous polyurethane dispersions via tetraphenylethane iniferters

Aqueous polyurethane (PU) dispersions containing tetraphenylethane iniferter groups were prepared from 4,4′-diphenylmethane diisocyanate, poly(propylene oxide)glycols, dimethylol propionic acid, and 1,1,2,2-tetraphenylethane-1,2-diol. To improve the water resistance of the dispersions, methyl methacrylate monomers were added into these dispersions and block-copolymerized onto the main PU chain. The viscosity and particle size of the dispersions were determined. Dispersion-cast films were characterized in terms of the contact angle, the swell in water, and the mechanical properties. Contact-angle and water-swell measurements showed that the hydrophilicity of the films was decreased significantly when methyl methacrylate was polymerized in the presence of tetraphenylethane containing aqueous PU dispersions.