Xiuju Lin,Bing Liao,Jialin Li,Jianheng Huang,Mangeng Lu,Hao Pang
In order to investigate the effect of double bond content in the crosslinkers on the performance of superplasticizers, three different crosslinked polycarboxylate superplasticizers were synthesized herein with various respective crosslinkers. Their impacts on the fluidity, absorption, and hydration behavior of cement systems were studied. The results showed that the polymer, which was synthesized using a crosslinker with four double bonds and five/six double bonds, had higher fluidity and the highest fluidity reached up to 395 mm at W/C of 0.35. Additionally, thermogravimetric analysis and hydration heat tests showed that the crosslinked polycarboxylate superplasticizers could prolong the hydration process of cement slurries. Among these three kinds of crosslinked polycarboxylate superplasticizers, the induction period of cement slurry containing the polymer with crosslinker of four double bonds was significantly extended to facilitate the processing of the concrete. The purpose of this study is to provide strategies for studying high-performance polycarboxylate superplasticizers with novel topological structure.
Guangqian Zhu,Liang Wang,Jia Kuang,Guangqiang Xu,Yongqiang Zhang,Qinggang Wang
The highly selective cationic polymerization of isoprene has been a great challenge over the last 70 years. Here, a synergistic Tf2NH-ionic liquid (IL) catalytic system has been developed to address this issue under mild conditions. Tf2NH serves as a highly efficient catalyst for the cationic polymerization with 0.01 mol % loading, and its counteranion IL serves as a remarkable selectivity-controlled medium delivering low-molecular-weight (Mn < 1500 g/mol) polyisoprenes with excellent yields (up to 99%), double bond content (DBs, up to 99%), and trans-1,4 selectivities (>95%). Mechanistic investigations indicated that an IL cation could effectively suppress the reprotonation of double bonds in polymer chains by reducing the electron density, leading to highly linear desired polymers. The industrial application prospects are illustrated by the IL recycling process, which could be used for more than five rounds with excellent yields and DBs.
危险品化学品经营许可证（带存储）