Synthesis of nanocomposites with anisotropic properties by controlled radical emulsion polymerization

Author(s)

Thaíssa de Camargo Chaparro

• Document type: Doctoral Thesis
• Press: Lorena.
• Institution: Universidade de São Paulo (USP). Escola de Engenharia de Lorena
• Defense date: 29 mar. 2016

Examining board members

Reinaldo Giudici; Elodie Bourgeat-lami; Philippe Cassagnau; Johan Pieter Anna Heuts; Vanessa Prévot; Amilton Martins dos Santos

• Advisor: Amilton Martins dos Santos

Abstract

The aim of this work is to prepare Laponite RD-based nanocomposite latexes by aqueous emulsion polymerization, using the reversible addition-fragmentation chain transfer (RAFT) polymerization. Laponite platelets were selected as the inorganic filler due, especially, to their anisotropic shape, which allows the production of nanostructured films, but also for their thermal and mechanical properties, their high chemical purity and the uniform dispersity of the platelets. Hydrophilic polymers (macroRAFT) composed of poly(ethylene glycol) (PEG), acrylic acid (AA) or N,N-dimethylaminoethyl methacrylate (DMAEMA) and comprising hydrophobic n-butyl acrylate (BA) units (in some cases) and trithiocarbonate terminal group were initially synthesized. Then, the interaction between the macroRAFTs and the clay was studied through the plot of adsorption isotherms. By acting as coupling agents and stabilizers, the macroRAFT agents were used in the emulsion copolymerization of methyl (meth)acrylate and BA by semi-continuous process in the presence of the clay. Hybrid latex particles with different morphologies were obtained and the results were associated to the nature and concentration of the RAFT (co)polymers, to the pH of the macroRAFT/Laponite dispersion, the glass transition temperature of the final copolymer (function of the composition of the hydrophobic monomers mixture) and to the polymerization conditions. The cryo-TEM images indicate the formation of polymerdecorated Laponite platelets (several latex particles located at the surface of the platelets), dumbbell-like, janus, Laponite-decorated (armored) latex particles, and multiple encapsulated particles (several platelets inside each latex particle). The mechanical properties of polymer/Laponite films were studied by dynamic mechanical analysis and correlated with the particles morphology and the films microstructure. (AU)

• FAPESP's process: 10/19919-6 - Synthesis of nanocomposites with anisotropic properties by controlled radical emulsion polymerization
• Grantee: Thaíssa de Camargo Chaparro
• Support type: Scholarships in Brazil - Doctorate (Direct)