Butadiene And Styrene Anionic Polymerization Initiated By Three Bimentallic Systerms At High Temperature

The investigation on the anionic polymerization was carried out to aim at the low concentration of monomer, low polymerization temperature and the high solvent consumption. Some anionic homo-and block-polymerization of styrene or butadiene was successfully obtained with cyclohexane as solvent, several bimetallic systems as initiator at high temperatures. And the microstructure of polymerization was studied in this paper.It suggested that the monomer conversion was influenced greatly by sodium hydride/tri-isobutyl aluminum (as [Na]/[Al]) ratio. The butadiene was almost not aggregated when [Na]/[Al]=1:1. NaH content was increased to raise butadiene conversion gradually and stabilized up to 85%. And when [Na]/[Al]<2:1, the design polymer molecular weight was different from the actual values widely, and the distribution was relatively wide. The content of polymerizer contains both cyclohexane soluble PB and the other precipitated from the solution. The 1H-NMR and IR spectra indicated that [Na]/[Al] ratio had little effect on microstructure of PB. The 1,2-content of soluble fraction was up to 30% or more, almost 1,2-content, trans-1,4-polybutadiene of insoluble part was 40%,37%. But [Na]/[Al]=1:1.5 was specialties, trans-1,4-polybutadiene of insoluble part as much as 55%.The retard anionic polymerization of styrene initiated by PBLi/i-Bu3Al at 70-120℃in cyclohexane was studied. The results showed that polymerization slowed down to complete stagnation with increasing [Al]/[Li]. The reaction rate increased with reaction temperature. The apparent activation energy of propagation reaction was 36-51kJ/mol at [Al]/[Li]=0.3-0.7, whereas it was 283kJ/mol when [Al]/[Li] increased to 1. These indicated that 2:1 PBLi/i-Bu3Al complex probably formed at low [Al]/[Li], which could initiate styrene rapidly at 70℃. And 1:1 complex formed at high [Al]/[Li], the plymerization. rate of which was considerable just at high temperature(≥100℃). The reactive activity of the former was higher than the latter and transformation might exist between them.Polybutadiene initiated by n-butyl lithium (n-BuLi)/dodecyl benzene sulfonate barium was studied. The results showed that the microstructure of polymer was little influenced as [Ba]/[Li] ratio and temperature.1,2-content maintained about 10%, and trans-1,4-polybutadiene was about 36-44%. Monomer conversion connecting with [Ba]/[Li] was at first increased and then decreased, reach up to 100%. When [Ba]/[Li]= 0.4 the monomer conversion was low very much. The highest conversion value appeared between the ratio of 0.2-0.3 rise the molecular weight was closed to the design value when rising temperature, and the weight distribution was between 1.2-1.5. The increase of Ba content in reduced activity of alkyl lithium initiator, but no effect on monomer insertion method, conversion decreasing with the Ba content increased. And raising the temperature is conducive to the actual molecular weight close to the design value.