具有离子响应性的聚(1-乙烯基-3-乙基咪唑四氟硼酸盐)@CaO微胶囊的表征及触发释放

Characteration and triggered release of ion-responsive poly(1-vinyl-3-ethylimidazolium tetrafluoroborate)@CaO microcapsules

采用相分离法合成了具有离子响应性的聚(1-乙烯基-3-乙基咪唑四氟硼酸盐)(PVEIm^+BF4^-)@CaO微胶囊。聚离子液体(PILs)的BF4-与水溶液中的Cl-发生离子交换使疏水性的交联PILs壳转变为亲水性,在水中形成亲水通道。PVEIm+BF4-@CaO微胶囊内部的CaO从通道被释放到水中形成Ca(OH)2。PVEIm^+BF4^-@CaO微胶囊加入后,NaCl水溶液中Cl-的浓度由8.3mmol·L^-1降低至5.8mmol·L^-1,pH值由7.00增加至11.83。提高反应物中的离子液体(ILs)的加入量、苯乙烯(St)∶二乙烯基苯(DVB)的质量比或水溶液中Cl-的浓度均可提高PVEIm+BF4-@CaO微胶囊中CaO的释放速率。不同含量单体组成的微胶囊或被不同浓度Cl-触发的微胶囊内的CaO均可被全部释放至NaCl溶液中。溶液中的最大Ca^2+浓度基本一致,约为3.4mmol·L^-1。SO42-也可触发微胶囊的释放。结果表明,PVEIm^+BF4^-@CaO微胶囊对Cl^-和SO4^2-具有良好的响应性。加入PVEIm^+BF4^-@CaO微胶囊后,NaCl水溶液中Cl^-/OH^-的浓度比显著降低,有利于提高钢筋的抗Cl-腐蚀能力。

The ion-responsive poly(1-vinyl-3-ethylimidazolium tetrafluoroborate)(PVEIm^+BF4^-)@CaO microcapsule was synthesized by phase separation. By the ion-exchange of BF4- on the poly(ionic liquids)(PILs) with Cl^- in water, the hydrophobic crosslinked PILs shell can be converted to hydrophilic and formed hydrophilic channels in water. The CaO in microcapsules can be released to water through the channels and transferred to Ca(OH)2. The addition of PVEIm+BF4-@CaO microcapsule to NaCl solution can reduce the Cl^- concentration from 8.3 mmolL^-1 to 5.8 mmolL^-1 and increase the pH from 7.00 to 11.83 simultaneously. The release rate of CaO shows a direct relationship with ionic liquids (ILs) content and the mass ratio of styrene(St):divinylbenzene(DVB). The increase of Cl^- concentration can result in the increase of CaO release rate. The CaO can be completely released to NaCl solution from PVEIm^+BF4^-@CaO microcapsules consisted with different mass ratios of monomers or triggered by various concentrations of Cl^-. The maximum Ca^2+ concentrations in the solution are similar, which is about 3.4 mmolL^-1. SO4^2- can also trigger the release of microcapsule. The results show that the PVEIm^+BF4^-@CaO microcapsules are sensitive to Cl^- and SO4^2-. The concentration ratio of Cl^-/OH^- decreases significantly after the PVEIm^+BF4^-@CaO microcapsules adding, which is beneficial to improve the corrosion resistance of steel bars to Cl^-.