3-(2,3-Dihydroxypropoxy)propyl-terminated polydimethylsiloxanes (DHT-PDMS) samples were prepared through the copolymerization of I,I,3,3,5,5,7,7-octamethylcyclotetrasiloxane (D4) and 1,3-bis[3-(2,3-dihydroxypropoxy)propyl]-1,1,3,3-tetramethyldisiloxane by acid-catalyzed equilibration. Their structures were characterized with IR and H-1-NMR spectra. The molecular weights were determined with gel permeation chromatography and H-1-NMR spectra, respectively. Differential scanning calorimetry and thermogravimetric analysis were used to investigate the thermodynamic properties and thermal degradation of DHT-PDMS. The effects of various factors on the synthesis of DHT-PDMS were also examined. However, the preparation of DHT-PDMS through the base-catalyzed equilibrium copolymerization of D, and l,3-bis[3-(2,3-epoxypropoxy)propyl]-1,1,3,3-tetramethyldisiloxane, followed by the hydrolysis of the epoxy groups, was unsuccessful. (C) 2004 Wiley Periodicals, Inc.