Study On The Anionic Synthesis Of Hydroxyl-Terminated Polybutadiene By Using Group-Protected Initator

In this paper, the new group-protected initiator 3-(t-butyldimethylsiloxy)-1-propyllithium, was synthesized at first. Then it was used to initiate the polymerization of butadiene to obtain the hydroxyl-terminated polybutadiene (HTPB). Comparing with the commonly used dilithium initiators, the pseudo-gel phenomenon which always happened during the end-capped process was successfully avoided. The linear HTPB was prepared by the following methods:end-capped with ethylene oxide, coupled with ethylene dibromide and hydrolyzed with acid. Correspondingly, the star HTPB could be synthesized just by changing the coupling agent to silicon tetrachloride or divinylbenzene (DVB).The THF was added as modifier in the butadiene anionic polymerization. Its effect on the microstucture of PB was studied by GPC, 'H-NMR. The results indicated that the polybutadiene showed high content of 1,4-structure (92.1%) after reacting for 20 hours at 30℃with the absence of modifier. The added THF made the content of 1,4-structure fall sharply, and assimilated with the designed molecular weight and the experimental molecular weight, and moreover, the narrowed polydispersity. The hydroxyl value of linear HTPB was examined. The degree of functionality approached 2. For the star HTPB, the coupling efficiency became higher while the more amount of coupling agent. Comparing the polymerization in 2L reactor with 250ml flask, the linking efficiency was much higher by two-step coupling procedures. The experiment results showed that when 1.2 times stoichiometric ratio coupling agent (silicon tetrachloride) was added to HTPB whose designed molecular weight was 15000, the coupling efficiency approached 95% and the degree of functionality approached 3.8. With the ratio of [DVB]/[Li]=5, the linking efficiency was 88.7% and the average arm number was 6.1.There was initial research about te reaction between HTPB and TDI performing as crosslinker. Hydroxyl-terminated polybuadiene polyturethane was tested by DMTA. The obtained Hydroxyl-terminated polybuadiene polyturethane produced by star HTPB ([DVB]/[Li]=5, Mw of each arm was 15000), its tensile-strength was 0.8 MPa and its elongation at break was 830%. The tgδvalue was 0.243 at 0℃, and 0.235 at 60℃respectively.