A novel type of crosslinkable waterborne polyurethane ionomer was prepared by the acetone process. Two new types of sulfonated diols compatible with this process were synthesized from dimethyl 5-sodium sulfo isophthalate using a one- or two-stage method. Isocyanate-terminated polyurethane oligomers were prepared from the sulfonated diols with various combinations of diols and diisocyanates and subsequently reacted with amino silane derivatives. Stable, low-volatile organic chemical, waterborne dispersions of the sulfo-urethane silanol polymers spontaneously crosslink upon drying without extra additives or processing steps. Despite the lack of organic coalescing solvents, the dispersions have minimum film-forming temperatures below 10 degreesC, regardless of glass-transition temperature. Tensile strengths up to 6000 psi with elongations between 300 and 600% were obtained for the crosslinked films. The hard-segment content of the films can be controlled to produce films with a Sward-Rocker hardness value up to 42. Through silane end-group modification, the crosslinking density of the films can also be modified to produce polyurethanes with a wide range of physical properties.