Clear polyurethane dispersions of nanometer size derived from carboxylic polycaprolactonediols

Aqueous polyurethanes dispersions of nanometer size derived from various carboxylic polycaprolactonediols of different molecular weights, carboxylic diols, including 2,2-di(hydroxymethyl)propanoic acid (DMPA), 2,2-di(hydroxymethyl)butanoic acid (DMBA), and di(4-isocyanatocyclohexyl)methane (HMDI) were prepared by a method in which the dispersing procedure was modified to enhance the molecular weight. The molecular weight, particle size, and UV–vis spectra of the polyurethane dispersions were investigated. The tensile properties of the cast films were determined. The modified dispersing procedure gave polyurethane dispersions with higher molecular weight and better tensile strength. As the molecular weight of the carboxylic polycaprolactonediol decreases, the content of the ionic groups increases, the particle size decreases accordingly. As the molecular weight of the carboxylic polycaprolactonediol used is 1000 g/mol or below, the polyurethanes dispersions become completely clear. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008