Synthesis of 1,3-Bis(4-Hydroxybutyl)tetramethyldisiloxane and alpha,omega-Bis(4-Hydroxybutyl) polydimethylsiloxane.

In this paper, using ethyl iodide and iodine as catalysts, 1,3-bis(4hydroxybutyl)tetramethyldisiloxane (BHBTMDS) was directly synthesized from dimethyldichlorosilane, purified tetrahydrofuran and magnesium powder. a.,w-Bis(4hydroxybutyl) polydimethylsiloxanes (HB-PDMSs) with different number-average molecular weights could be prepared through the reaction of 1,3-bis(4hydroxybutyl)tetramethyldisiloxane and dimethoxydimethyl silane in the presence of a stoichiometric amount of water and hydrochloric acid. Structures of BHBTMDS and HB-PDMS were characterized by Fourier transform infrared (FTIR) spectroscopy and high-resolution 1H NMR. The number-average molecular weights of these hydroxybutyl-terminated polydimethylsiloxanes could be determined fairly by end group titration method. The results from FTIR and high-resolution 1H NMR clearly illustrated the successful syntheses of BHBTMDS and HB-PDMS. The number-average molecular weight of HB-PDMS obtained was higher than the targeted molecular weight. When the molecular weight is lower, the deviation between targeted number-average molecular weight and experimental number-average molecular weight was larger. At number-average molecular weight higher than 5,000 g/mol smaller deviation was observed.