Chaparro Thaíssa de Camargo, Silva Rodrigo Duarte, Monteiro Igor Stefanichen, Barros-Timmons A, Giudici Reinaldo, Martins Dos Santos Amilton, Bourgeat-Lami Elodie
Univ Lyon, Université Claude Bernard Lyon 1, CPE Lyon, CNRS, UMR 5265, Chemistry, Catalysis, Polymers and Processes (C2P2) , 43, Bvd du 11 Novembre 1918 , F-69616 Villeurbanne , France.
Engineering School of Lorena , University of São Paulo , 12.602-810 Lorena , SP , Brazil.
Langmuir. 2019 Sep 3;35(35):11512-11523. doi: 10.1021/acs.langmuir.9b01987. Epub 2019 Aug 22.
The functionalization of Laponite RD platelets with different cationic, anionic, and nonionic homo- and copolymers synthesized by reversible addition-fragmentation chain transfer (RAFT) has been investigated. The effective interaction of the macromolecular RAFT agents (macroRAFTs) with the inorganic particles is known to be of crucial importance for the successful coating of minerals with polymers via RAFT-mediated emulsion polymerization to produce polymer-encapsulated inorganic particles. The macroRAFT agents synthesized in the present work contain carefully selected reinitiating R groups, which bear either ionizable tertiary amine or quaternary ammonium moieties (from 2-(dimethylamino)ethyl methacrylate, DMAEMA), negatively charged acrylic acid (AA) repeat units, or neutral polyethylene glycol (PEG) side chains, and are capable of interacting with Laponite via different adsorption mechanisms. The equilibrium adsorption of these RAFT (co)polymers was investigated by the plotting of adsorption isotherms, and either L-type or H-type curves were obtained. The hydrophobicity of the macroRAFT was shown to promote adsorption, as did the pending configuration of the PEG block. Charge repulsion between AA and the negatively charged surface of Laponite at pH 7.5, on the other hand, was prejudicial for adsorption, while the strong electrostatic interaction between the cationic DMAEMA molecules and the Laponite surface led to high-affinity-type curves.
通过可逆加成-断裂链转移（RAFT）合成的不同阳离子、阴离子和非离子均聚物及共聚物对锂皂石RD片状颗粒进行功能化的研究已经展开。已知大分子RAFT试剂（macroRAFTs）与无机颗粒的有效相互作用对于通过RAFT介导的乳液聚合用聚合物成功包覆矿物以制备聚合物包裹的无机颗粒至关重要。本工作中合成的macroRAFT试剂含有精心选择的再引发R基团，这些基团带有可电离的叔胺或季铵部分（来自甲基丙烯酸2-(二甲氨基)乙酯，DMAEMA）、带负电荷的丙烯酸（AA）重复单元或中性聚乙二醇（PEG）侧链，并且能够通过不同的吸附机制与锂皂石相互作用。通过绘制吸附等温线研究了这些RAFT（共）聚合物的平衡吸附，得到了L型或H型曲线。结果表明，macroRAFT的疏水性促进了吸附，PEG嵌段的悬垂构型也有同样的作用。另一方面，在pH 7.5时，AA与锂皂石带负电荷表面之间的电荷排斥不利于吸附，而阳离子DMAEMA分子与锂皂石表面之间的强静电相互作用导致了高亲和力型曲线。
