Abstract
Three amine-functionalized 1,1-diphenylethylene (DPE) derivatives (DPE-(NMe2)(2), DPE-NMe2 and DPESiH/NMe2) 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 H-1 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 kg) 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 kg) experimental values of DPE-(NMe2)(2), DPE-NMe2 and DPE-SiH/NMe2 were found to be 0.155 x 10(-3), 1.26 x 10(-3), and 6.24 x 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 DPENMe2 and DPE-SiH/NMe2 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. (C) 2018 Elsevier Ltd. All rights reserved.