The acetylation reaction of polytetramethylene glycol (PTMG) with acetic anhydride in pyridine was studied. The extent of acetylation was measured by H-1-NMR, and the acetylation product was characterized with FTIR, H-1-NMR, and C-13-NMR. The effects of the experimental conditions, i.e., reaction time and temperature, acetylation reagent concentration (anhydride and hydroxyl molar ratio), were investigated. The increase in reaction temperature and reaction time favored the acetylation yields. (c) 2007 Wiley Periodicals, Inc.