Investigation of the Adsorption of Amphipathic macroRAFT Agents onto Montmorillonite Clay

Author(s)

Silva, Rodrigo Duarte ^[1] ; Monteiro, Igor Stefanichen ^[1] ; Chaparro, Thaissa de Camargo ^{[1, 2]} ; Hardt, Raissa Silva ^[1] ; Giudici, Reinaldo ^[3] ; Barros-Timmons, A. ^[4] ; Bourgeat-Lami, Elodie ^[2] ; dos Santos, Amilton Martins ^[1]

Affiliation

^[1] Univ Sao Paulo, Engn Sch Lorena, Lab Polymers, BR-12602810 Lorena, SP - Brazil

^[2] Univ Lyon 1, CPE Lyon, CNRS, UMR 5265, C2P2, 43 Bvd 11 Novembre 1918, F-69616 Villeurbanne - France

^[3] Univ Sao Paulo, Polytech Sch, Dept Chem Engn, BR-05508010 Sao Paulo, SP - Brazil

^[4] Univ Aveiro, Dept Chem, CICECO Aveiro Inst Mat, Campus Univ Santiago, P-3810193 Aveiro - Portugal

• Document type: Journal article
• Source: Langmuir; v. 33, n. 38, p. 9598-9608, SEP 26 2017.
• Web of Science Citations: 6

Abstract

Recently, there has been significant interest in the use of the reversible addition-fragmentation chain-transfer (RAFT) technique to generate a variety of organic/inorganic colloidal composite particles in aqueous dispersed media using the so-called macroRAFT-assisted encapsulating emulsion polymerization (REEP) strategy. In this process, special attention should be paid to the adsorption of the macro molecular RAFT (macroRAFT) agent onto the inorganic particles, as it determines the final particle morphology and can also influence latex stability. In this work, different amphipathic macroRAFT agents were synthesized by RAFT, and their adsorption onto commercial Montmorillonite clay Cloisite Na+ (MMT) was studied by means of adsorption isotherms. Three types of macroRAFT agents were considered: a nonionic one based on poly(ethylene glycol) methyl ether acrylate (PEGA) and n-butyl acrylate (BA), anionic ones, including a block copolymer and random copolymers, based on acrylic acid (AA), BA and PEGA, and cationic ones based on 2-(dimethylamino)ethyl methacrylate (DMAEMA), BA and PEGA. Six adsorption isotherm models (Langmuir, Freundlich, Tempkin, Redlich-Peterson, Sips, and Brunauer-Emmett-Teller) were adjusted to the, experimental isotherms. The nonionic macroRAFT agent formed a monolayer on the clay surface with a maximum adsorption capacity of 400 mg g(-1) at pH 8, as determined from the Sips adsorption model. Adsorption of the AA-based macroRAFT agents onto MMT was moderate at alkaline pH due to electrostatic repulsions, but increased with decreasing pH. The DMAEMA-based macroRAFT agents displayed a much stronger interaction with the oppositely charged MMT surface at acidic pH due to electrostatic interactions, and the concentration of adsorbed macroRAFT agent reached values as high as 800 mg g(-1). The BET model fitted the experimental data relatively well indicating multilayer adsorption promoted by the presence of the hydrophobic BA units. In addition, the cationic macroRAFT agents afforded stable MMT/macroRAFT agent complexes as evaluated by dynamic light scattering and zeta potential analyses. (AU)

• FAPESP's process: 10/50383-5 - Polymer-encapsulation of anisotropic inorganic particles by raft-mediated emulsion polymerization
• Grantee: Amilton Martins dos Santos
• Support Opportunities: Regular Research Grants
• FAPESP's process: 11/20533-8 - Encapsulation of montmorillonite through RAFT controlled radical polymerization in emulsion for the production of nanostructured films with anisotropic properties
• Grantee: Rodrigo Duarte Silva
• Support Opportunities: Scholarships in Brazil - Doctorate