The dynamics of living polymerization of styrene was studied with alkyllithium/potassium alkoxide as bimetallic initiator and cyclohexane as solvent. It was found that the apparent propagation rate constants ( k ap )i...The dynamics of living polymerization of styrene was studied with alkyllithium/potassium alkoxide as bimetallic initiator and cyclohexane as solvent. It was found that the apparent propagation rate constants ( k ap )increased greatly with little increasing of K/Li ratios and in linear relationships with the concentrations of potassium alkoxide (\)when K/Li ratios were lower that 0 1. And the slopes of k ap \|\ lines increased with the decreasing of alkyllithium concentrations. This dynamics feature can not be explained quantitatively by the ordinary association dynamics model which ignored the cross\|association between the propagation species with different metallic ion. In this paper, a new dynamics model on cross\|association concept was established and the dynamics feature of living polymerization of styrene can be interpreted satisfactorily. The propagation rate constant of potassium species(\%k\%\-k) and the constant group, (\%K\%\-1/2)\+\{0.5\}/\%K\%\-3, of dissociation constants of cross\|association species (\%K\%\-3)and lithium species (\%K\%\-1)were derived by curve fitting and led to values of 7 1 ×10 3(mol/L)\+\{-1\}min\+\{-1\} and 67 (mol/L) \+\{-0.5\} respectively at a polymerization temperature of 50℃.展开更多
文摘The dynamics of living polymerization of styrene was studied with alkyllithium/potassium alkoxide as bimetallic initiator and cyclohexane as solvent. It was found that the apparent propagation rate constants ( k ap )increased greatly with little increasing of K/Li ratios and in linear relationships with the concentrations of potassium alkoxide (\)when K/Li ratios were lower that 0 1. And the slopes of k ap \|\ lines increased with the decreasing of alkyllithium concentrations. This dynamics feature can not be explained quantitatively by the ordinary association dynamics model which ignored the cross\|association between the propagation species with different metallic ion. In this paper, a new dynamics model on cross\|association concept was established and the dynamics feature of living polymerization of styrene can be interpreted satisfactorily. The propagation rate constant of potassium species(\%k\%\-k) and the constant group, (\%K\%\-1/2)\+\{0.5\}/\%K\%\-3, of dissociation constants of cross\|association species (\%K\%\-3)and lithium species (\%K\%\-1)were derived by curve fitting and led to values of 7 1 ×10 3(mol/L)\+\{-1\}min\+\{-1\} and 67 (mol/L) \+\{-0.5\} respectively at a polymerization temperature of 50℃.
