A new synthesis for polyurethane dispersions was developed using both trimellitic anhydride alone and in combination with dimethylol propionic acid as internal emulsifiers. During synthesis of the polyurethane ionomer, Fourier transform infrared spectroscopy was used for monitoring and characterizing both the polyaddition step and the anhydride ring opening process. Depending on the synthesis route, the carboxylic groups are either located at the end of the polymer backbone or additionally statistically distributed within the polymer chain itself. The effect of the carboxylic group's position on the chemical and physical properties, with particular reference to particle size and pH, was analyzed. Three different polyols were used to synthesize the polyurethane dispersions. Driven by the current trend to find renewable alternatives to petrochemical-based raw materials, one bio-based polyol was included for the synthesis. The effect of the different structures of the polyurethane dispersions (petrochemical- or bio-based polyols) on mechanical properties and thermal behavior was investigated. (c) 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 680-690