Anionomer prepolymers based on poly(propylene oxide) (PPG), 4,4’-dicyclohexylmethane diisocyanate (H(12)MDI) and dimethylol propionic acid (DMPA) were synthesized in bulk. The molecular weight of the prepolymers was determined by vapour pressure osmometry (VPO) and gel permeation chromatography (GPC).