The effect of amine-functionalized 1,1-diphenylethylene (DPE) derivatives on end-capping reactions and the simulation of their precision for sequence control
Three amine-functionalized 1,1-diphenylethylene (DPE) derivatives (DPE-(NMe 2 ) 2 , DPE-NMe 2 and DPE-SiH/NMe 2 ) were used to study the end-capping reactions of poly(styryl)lithium (PS-Li) for investigating the effect on end-capping of electron-donating groups in DPE structures. In situ 1 H NMR was used to measure the kinetic parameters of end-capping reactions. When the DPE derivative was held constant in the PS-Li capping reaction, the kinetic parameter (k SD ) did not change with the variance of either concentration or degree of polymerization of PS-Li. Additionally, the k SD value changed dramatically when various electronic properties of the DPE derivative substituents were modified. Electron-withdrawing groups accelerated the end-capping reaction, while electron-donating groups decelerated it. The k SD experimental values of DPE-(NMe 2 ) 2 , DPE-NMe 2 and DPE-SiH/NMe 2 were found to be 0.155 × 10 −3 , 1.26 × 10 −3 , and 6.24 × 10 −3 L 1/2 mol −1/2 s −1 , respectively. An intuitive model was established to simulate the precision of the sequence-controlled copolymerization with DPE derivatives based on investigations of end-capping kinetics. The model depicts the degree of fictitious styrene propagation for the chain insertion of one DPE derivative unit. The fictitious degrees of polymerization of styrene (FDPs) for DPE-NMe 2 and DPE-SiH/NMe 2 were calculated to be 37 and 13, respectively, suggesting that using DPE derivatives containing an electron-withdrawing group in the synthesis of sequence-controlled polymers might lead to a more precise structure.
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